< draft-ietf-opsawg-capwap-alt-tunnel   rfc8350.txt 
Opsawg Working Group R. Zhang Internet Engineering Task Force (IETF) R. Zhang
Internet-Draft China Telecom Request for Comments: 8350 China Telecom
Intended status: Experimental R. Pazhyannur Category: Experimental R. Pazhyannur
Expires: August 2, 2018 S. Gundavelli ISSN: 2070-1721 S. Gundavelli
Cisco Cisco
Z. Cao Z. Cao
H. Deng H. Deng
Z. Du Z. Du
Huawei Huawei
January 29, 2018 April 2018
Alternate Tunnel Encapsulation for Data Frames in CAPWAP Alternate Tunnel Encapsulation for Data Frames in
draft-ietf-opsawg-capwap-alt-tunnel-12 Control and Provisioning of Wireless Access Points (CAPWAP)
Abstract Abstract
Control and Provisioning of Wireless Access Points (CAPWAP) defines a Control and Provisioning of Wireless Access Points (CAPWAP) is a
specification to encapsulate a station's data frames between the protocol for encapsulating a station's data frames between the
Wireless Transmission Point (WTP) and Access Controller (AC). Wireless Transmission Point (WTP) and Access Controller (AC).
Specifically, the station's IEEE 802.11 data frames can be either Specifically, the station's IEEE 802.11 data frames can be either
locally bridged or tunneled to the AC. When tunneled, a CAPWAP data locally bridged or tunneled to the AC. When tunneled, a CAPWAP Data
channel is used for tunneling. In many deployments encapsulating Channel is used for tunneling. In many deployments, encapsulating
data frames to an entity other than the AC (for example to an Access data frames to an entity other than the AC (for example, to an Access
Router (AR)) is desirable. Furthermore, it may also be desirable to Router (AR)) is desirable. Furthermore, it may also be desirable to
use different tunnel encapsulation modes between the WTP and the use different tunnel encapsulation modes between the WTP and the
Access Router. This document defines extension to CAPWAP protocol Access Router. This document defines an extension to the CAPWAP
for supporting this capability and refers to it as alternate tunnel protocol that supports this capability and refers to it as alternate
encapsulation. The alternate tunnel encapsulation allows 1) the WTP tunnel encapsulation. The alternate tunnel encapsulation allows 1)
to tunnel non-management data frames to an endpoint different from the WTP to tunnel non-management data frames to an endpoint different
the AC and 2) the WTP to tunnel using one of many known encapsulation from the AC and 2) the WTP to tunnel using one of many known
types such as IP-IP, IP-GRE, CAPWAP. The WTP may advertise support encapsulation types, such as IP-IP, IP-GRE, or CAPWAP. The WTP may
for alternate tunnel encapsulation during the discovery and join advertise support for alternate tunnel encapsulation during the
process and AC may select one of the supported alternate tunnel discovery and join process, and the AC may select one of the
encapsulation types while configuring the WTP. supported alternate tunnel encapsulation types while configuring the
WTP.
Status of This Memo Status of This Memo
This Internet-Draft is submitted in full conformance with the This document is not an Internet Standards Track specification; it is
provisions of BCP 78 and BCP 79. published for examination, experimental implementation, and
evaluation.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months This document defines an Experimental Protocol for the Internet
and may be updated, replaced, or obsoleted by other documents at any community. This document is a product of the Internet Engineering
time. It is inappropriate to use Internet-Drafts as reference Task Force (IETF). It represents the consensus of the IETF
material or to cite them other than as "work in progress." community. It has received public review and has been approved for
publication by the Internet Engineering Steering Group (IESG). Not
all documents approved by the IESG are candidates for any level of
Internet Standard; see Section 2 of RFC 7841.
This Internet-Draft will expire on August 2, 2018. Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc8350.
Copyright Notice Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . 7 1.1. Conventions Used in This Document . . . . . . . . . . . . 7
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 7
1.3. History of the document . . . . . . . . . . . . . . . . . 8 1.3. History of the Document . . . . . . . . . . . . . . . . . 8
2. Alternate Tunnel Encapsulation Overview . . . . . . . . . . . 8 2. Alternate Tunnel Encapsulation Overview . . . . . . . . . . . 9
3. CAPWAP Protocol Message Elements Extensions . . . . . . . . . 11 3. Extensions for CAPWAP Protocol Message Elements . . . . . . . 11
3.1. Supported Alternate Tunnel Encapsulations . . . . . . . . 11 3.1. Supported Alternate Tunnel Encapsulations . . . . . . . . 11
3.2. Alternate Tunnel Encapsulations Type . . . . . . . . . . 11 3.2. Alternate Tunnel Encapsulations Type . . . . . . . . . . 11
3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication . . . 12 3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication . . . 12
4. Alternate Tunnel Types . . . . . . . . . . . . . . . . . . . 13 4. Alternate Tunnel Types . . . . . . . . . . . . . . . . . . . 13
4.1. CAPWAP based Alternate Tunnel . . . . . . . . . . . . . . 13 4.1. CAPWAP-Based Alternate Tunnel . . . . . . . . . . . . . . 13
4.2. PMIPv6 based Alternate Tunnel . . . . . . . . . . . . . . 14 4.2. PMIPv6-Based Alternate Tunnel . . . . . . . . . . . . . . 14
4.3. GRE based Alternate Tunnel . . . . . . . . . . . . . . . 15 4.3. GRE-Based Alternate Tunnel . . . . . . . . . . . . . . . 15
5. Alternate Tunnel Information Elements . . . . . . . . . . . . 15 5. Alternate Tunnel Information Elements . . . . . . . . . . . . 16
5.1. Access Router Information Elements . . . . . . . . . . . 15 5.1. Access Router Information Elements . . . . . . . . . . . 16
5.1.1. AR IPv4 List Element . . . . . . . . . . . . . . . . 16 5.1.1. AR IPv4 List Element . . . . . . . . . . . . . . . . 16
5.1.2. AR IPv6 List Element . . . . . . . . . . . . . . . . 16 5.1.2. AR IPv6 List Element . . . . . . . . . . . . . . . . 17
5.2. Tunnel DTLS Policy Element . . . . . . . . . . . . . . . 17 5.2. Tunnel DTLS Policy Element . . . . . . . . . . . . . . . 17
5.3. IEEE 802.11 Tagging Mode Policy Element . . . . . . . . . 19 5.3. IEEE 802.11 Tagging Mode Policy Element . . . . . . . . . 19
5.4. CAPWAP Transport Protocol Element . . . . . . . . . . . . 20 5.4. CAPWAP Transport Protocol Element . . . . . . . . . . . . 20
5.5. GRE Key Element . . . . . . . . . . . . . . . . . . . . . 22 5.5. GRE Key Element . . . . . . . . . . . . . . . . . . . . . 22
5.6. IPv6 MTU Element . . . . . . . . . . . . . . . . . . . . 23 5.6. IPv6 MTU Element . . . . . . . . . . . . . . . . . . . . 23
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 23 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 24
7. Security Considerations . . . . . . . . . . . . . . . . . . . 25 7. Security Considerations . . . . . . . . . . . . . . . . . . . 25
8. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 25 8. References . . . . . . . . . . . . . . . . . . . . . . . . . 25
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 25 8.1. Normative References . . . . . . . . . . . . . . . . . . 25
9.1. Normative References . . . . . . . . . . . . . . . . . . 25 8.2. Informative References . . . . . . . . . . . . . . . . . 27
9.2. Informative References . . . . . . . . . . . . . . . . . 26 Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 28
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 27 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 28
1. Introduction 1. Introduction
Service Providers are deploying very large Wi-Fi network containing Service Providers are deploying very large Wi-Fi networks containing
hundreds of thousands of Access Points (APs), which are referred to hundreds of thousands of Access Points (APs), which are referred to
as Wireless Transmission Points (WTPs) in Control and Provisioning of as Wireless Transmission Points (WTPs) in Control and Provisioning of
Wireless Access Points (CAPWAP) terminology [RFC5415]. These Wireless Access Points (CAPWAP) terminology [RFC5415]. These
networks are designed to carry traffic generated from mobile users. networks are designed to carry traffic generated from mobile users.
The volume in mobile user traffic is already very large and expected The volume in mobile user traffic is already very large and expected
to continue growing rapidly. As a result, operators are looking for to continue growing rapidly. As a result, operators are looking for
scalable solutions that can meet the increasing demand. The scalable solutions that can meet the increasing demand. The
scalability requirement can be met by splitting the control/ scalability requirement can be met by splitting the control/
management plane from the data plane. This enables the data plane to management plane from the data plane. This enables the data plane to
scale independent of the control/management plane. This scale independent of the control/management plane. This
specification provides a way to enable such separation. specification provides a way to enable such separation.
CAPWAP ([RFC5415], [RFC5416]) defines a tunnel mode that describes CAPWAP [RFC5415] [RFC5416] defines a tunnel mode that describes how
how the WTP handles the data plane (user traffic). The following the WTP handles the data plane (user traffic). The following types
types are defined: are defined:
o Local Bridging: All data frames are locally bridged. o Local Bridging: All data frames are locally bridged.
o 802.3 Tunnel: All data frames are tunneled to the Access
Controller (AC) in 802.3 format. o IEEE 802.3 Tunnel: All data frames are tunneled to the Access
o 802.11 Tunnel: All data frames are tunneled to the AC in 802.11 Controller (AC) in IEEE 802.3 format.
format.
o IEEE 802.11 Tunnel: All data frames are tunneled to the AC in IEEE
802.11 format.
Figure 1 describes a system with Local Bridging. The AC is in a Figure 1 describes a system with Local Bridging. The AC is in a
centralized location. The data plane is locally bridged by the WTPs centralized location. The data plane is locally bridged by the WTPs;
leading to a system with centralized control plane with distributed this leads to a system with a centralized control plane and a
data plane. This system has two benefits: 1) reduces the scale distributed data plane. This system has two benefits: 1) it reduces
requirement on data traffic handling capability of the AC and 2) the scale requirement on the data traffic handling capability of the
leads to more efficient/optimal routing of data traffic while AC, and 2) it leads to more efficient/optimal routing of data traffic
maintaining centralized control/management. while maintaining centralized control/management.
Locally Bridged Locally Bridged
+-----+ Data Frames +----------------+ +-----+ Data Frames +----------------+
| WTP |===============| Access Router | | WTP |===============| Access Router |
+-----+ +----------------+ +-----+ +----------------+
\\ \\
\\ CAPWAP Control Channel +----------+ \\ CAPWAP Control Channel +----------+
++=========================| AC | ++=========================| AC |
// CAPWAP Data Channel: | | // CAPWAP Data Channel: | |
// IEEE 802.11 Mgmt traffic +----------+ // IEEE 802.11 Mgmt Traffic +----------+
// //
+-----+ +----------------+ +-----+ +----------------+
| WTP |============== | Access Router | | WTP |============== | Access Router |
+-----+ +----------------+ +-----+ +----------------+
Locally Bridged Locally Bridged
Data Frames Data Frames
Figure 1: Centralized Control with Distributed Data Figure 1: Centralized Control with Distributed Data
The AC handles control of WTPs. In addition, the AC also handles the The AC handles control of WTPs. In addition, the AC also handles the
IEEE 802.11 management traffic to/from the stations. There is CAPWAP IEEE 802.11 management traffic to/from the stations. There is a
Control and Data Channel between the WTP and the AC. Note that even CAPWAP Control and Data Channel between the WTP and the AC. Note
though there is no user traffic transported between the WTP and AC, that even though there is no user traffic transported between the WTP
there is still a CAPWAP Data Channel. The CAPWAP Data Channel and AC, there is still a CAPWAP Data Channel. The CAPWAP Data
carries the IEEE 802.11 management traffic (like IEEE 802.11 Action Channel carries the IEEE 802.11 management traffic (like IEEE 802.11
Frames). Action Frames).
Figure 2 shows a system where the tunnel mode is configured to tunnel Figure 2 shows a system where the tunnel mode is configured to tunnel
data frames between the WTP and the AC either using 802.3 Tunnel or data frames between the WTP and the AC using either the IEEE 802.3
802.11 Tunnel configurations. Operators deploy this configuration Tunnel or 802.11 Tunnel configurations. Operators deploy this
when they need to tunnel the user traffic. The tunneling requirement configuration when they need to tunnel the user traffic. The
may be driven by the need to apply policy at the AC. This tunneling requirement may be driven by the need to apply policy at
requirement could be met in the locally bridged system (Figure 1) if the AC. This requirement could be met in the locally bridged system
the Access Router (AR) implemented the required policy. However, in (Figure 1) if the Access Router (AR) implemented the required policy.
many deployments the operator managing the WTP is different than the However, in many deployments, the operator managing the WTP is
operator managing the Access Router. When the operators are different than the operator managing the Access Router. When the
different, the policy has to be enforced in a tunnel termination operators are different, the policy has to be enforced in a tunnel
point in the WTP operator's network. termination point in the WTP operator's network.
+-----+ +-----+
| WTP | | WTP |
+-----+ +-----+
\\ \\
\\ CAPWAP Control Channel +----------+ \\ CAPWAP Control Channel +----------+
++=========================| AC | ++=========================| AC |
// CAPWAP Data Channel: | | // CAPWAP Data Channel: | |
// IEEE 802.11 Mgmt traffic | | // IEEE 802.11 Mgmt Traffic | |
// Data Frames +----------+ // Data Frames +----------+
// //
+-----+ +-----+
| WTP | | WTP |
+-----+ +-----+
Figure 2: Centralized Control and Centralized Data Figure 2: Centralized Control and Centralized Data
The key difference with the locally bridged system is that the data The key difference with the locally bridged system is that the data
frames are tunneled to the AC instead of being locally bridged. frames are tunneled to the AC instead of being locally bridged.
There are two shortcomings with the system in Figure 2. 1) They do There are two shortcomings with the system in Figure 2: 1) it does
not allow the WTP to tunnel data frames to an endpoint different from not allow the WTP to tunnel data frames to an endpoint different from
the AC and 2) They do not allow the WTP to tunnel data frames using the AC, and 2) it does not allow the WTP to tunnel data frames using
any encapsulation other than CAPWAP (as specified in Section 4.4.2 of any encapsulation other than CAPWAP (as specified in Section 4.4.2 of
[RFC5415]). [RFC5415]).
Figure 3 shows a system where the WTP tunnels data frames to an Figure 3 shows a system where the WTP tunnels data frames to an
alternate entity different from the AC. The WTP also uses an alternate entity different from the AC. The WTP also uses an
alternate tunnel encapsulation such as L2TP, L2TPv3, IP-in-IP, IP/ alternate tunnel encapsulation such as Layer 2 Tunneling Protocol
GRE, etc. This enables 1) independent scaling of data plane and 2) (L2TP), L2TPv3, IP-in-IP, IP/GRE, etc. This enables 1) independent
leveraging of commonly used tunnel encapsulations such as L2TP, GRE, scaling of data plane and 2) leveraging of commonly used tunnel
etc. encapsulations such as L2TP, GRE, etc.
Alternate Tunnel to AR (L2TPv3, IP-IP, CAPWAP, etc.) Alternate Tunnel to AR (L2TPv3, IP-IP, CAPWAP, etc.)
_________ _________
+-----+ ( ) +-----------------+ +-----+ ( ) +-----------------+
| WTP |======+Internet +==============|Access Router(AR)| | WTP |======+Internet +==============|Access Router(AR)|
+-----+ (_________) +-----------------+ +-----+ (_________) +-----------------+
\\ ________ CAPWAP Control \\ ________ CAPWAP Control
\\ ( ) Channel +--------+ \\ ( ) Channel +--------+
++=+Internet+========================| AC | ++=+Internet+========================| AC |
// (________)CAPWAP Data Channel: +--------+ // (________)CAPWAP Data Channel: +--------+
// IEEE 802.11 Mgmt traffic // IEEE 802.11 Mgmt Traffic
// _________ // _________
+-----+ ( ) +----------------+ +-----+ ( ) +----------------+
| WTP |====+Internet +================| Access Router | | WTP |====+Internet +================| Access Router |
+-----+ (_________) +----------------+ +-----+ (_________) +----------------+
Alternate Tunnel to AR (L2TPv3, IP-in-IP, CAPWAP, etc.) Alternate Tunnel to AR (L2TPv3, IP-in-IP, CAPWAP, etc.)
Figure 3: Centralized Control with Alternate Tunnel for Data Figure 3: Centralized Control with an Alternate Tunnel for Data
The WTP may support widely used encapsulation types such as L2TP, The WTP may support widely used encapsulation types such as L2TP,
L2TPv3, IP-in-IP, IP/GRE, etc. The WTP advertises the different L2TPv3, IP-in-IP, IP/GRE, etc. The WTP advertises the different
alternate tunnel encapsulation types it can support. The AC alternate tunnel encapsulation types it can support. The AC
configures one of the advertised types. As shown in the figure there configures one of the advertised types. As is shown in Figure 3,
is a CAPWAP control and data channel between the WTP and AC. The there is a CAPWAP Control and Data Channel between the WTP and AC.
CAPWAP data channel carries the stations' management traffic as in The CAPWAP Data Channel carries the stations' management traffic, as
the case of the locally bridged system. The main reason to maintain in the case of the locally bridged system. The main reason to
a CAPWAP data channel is to maintain similarity with the locally maintain a CAPWAP Data Channel is to maintain similarity with the
bridged system. The WTP maintains three tunnels: CAPWAP Control, locally bridged system. The WTP maintains three tunnels: CAPWAP
CAPWAP Data, and another alternate tunnel for the data frames. The Control, CAPWAP Data, and another alternate tunnel for the data
data frames are transported by an alternate tunnel between the WTP frames. The data frames are transported by an alternate tunnel
and a tunnel termination point such as an Access Router. This between the WTP and a tunnel termination point, such as an Access
specification describes how the alternate tunnel can be established. Router. This specification describes how the alternate tunnel can be
The specification defines message elements for the WTP to advertise established. The specification defines message elements for the WTP
support for alternate tunnel encapsulation, for the AC to configure to advertise support for alternate tunnel encapsulation, for the AC
alternate tunnel encapsulation, and for the WTP to report failure of to configure alternate tunnel encapsulation, and for the WTP to
the alternate tunnel. report failure of the alternate tunnel.
The alternate tunnel encapsulation also supports the third-party WLAN The alternate tunnel encapsulation also supports the third-party WLAN
service provider scenario (i.e. Virtual Network Operator, VNO). service provider scenario (i.e., Virtual Network Operator (VNO)).
Under this scenario, the WLAN provider owns the WTP and AC resources, Under this scenario, the WLAN provider owns the WTP and AC resources
while the VNOs can rent the WTP resources from the WLAN provider for while the VNOs can rent the WTP resources from the WLAN provider for
network access. The AC belonging to the WLAN service provider network access. The AC belonging to the WLAN service provider
manages the WTPs in the centralized mode. manages the WTPs in the centralized mode.
As shown in Figure 4, VNO 1&2 don't possess the network access As shown in Figure 4, VNO 1 and VNO 2 don't possess the network
resources, however they provide services by acquiring resources from access resources; however, they provide services by acquiring
the WLAN provider. Since a WTP is capable of supporting up to 16 resources from the WLAN provider. Since a WTP is capable of
Service Set Identifiers (SSIDs), the WLAN provider may provide supporting up to 16 Service Set Identifiers (SSIDs), the WLAN
network access service for different providers with different SSIDs. provider may provide network access service for different providers
For example, SSID1 is advertised by the WTP for VNO1; while SSID2 is with different SSIDs. For example, SSID1 is advertised by the WTP
advertised by the WTP for VNO2. Therefore the data traffic from the for VNO 1 while SSID2 is advertised by the WTP for VNO 2. Therefore,
user can be directly steered to the corresponding access router of the data traffic from the user can be directly steered to the
the VNO who owns that user. As shown in Figure 4, AC can notify corresponding Access Router of the VNO who owns that user. As is
multiple AR addresses for load balancing or redundancy. shown in Figure 4, AC can notify multiple AR addresses for load
balancing or redundancy.
+----+ +----+
| AC | | AC |
+--+-+ +--+-+
CAPWAP-CTL | CAPWAP-CTL |
+-----------------+ +-----------------+
| CAPWAP-DATA: IEEE 802.11 Mgmt traffic | CAPWAP-DATA: IEEE 802.11 Mgmt Traffic
| |
WLAN Provider| VNO 1 WLAN Provider| VNO 1
+-----+ CAPWAP-DATA (SSID1) +---------------+ +-----+ CAPWAP-DATA (SSID1) +---------------+
SSID1 | WTP +--------------------------|Access Router 1| SSID1 | WTP +--------------------------|Access Router 1|
SSID2 +--+-++ +---------------+ SSID2 +--+-++ +---------------+
| | | |
| | VNO 1 | | VNO 1
| | GRE-DATA (SSID1) +---------------+ | | GRE-DATA (SSID1) +---------------+
| +---------------------------|Access Router 2| | +---------------------------|Access Router 2|
| +---------------+ | +---------------+
| |
| VNO 2 | VNO 2
| CAPWAP-DATA (SSID2) +---------------+ | CAPWAP-DATA (SSID2) +---------------+
+-----------------------------|Access Router 3| +-----------------------------|Access Router 3|
+---------------+ +---------------+
Figure 4: Third-party WLAN Service Provider Figure 4: Third-Party WLAN Service Provider
1.1. Conventions used in this document 1.1. Conventions Used in This Document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
document are to be interpreted as described in [RFC2119]. "OPTIONAL" in this document are to be interpreted as described in
BCP 14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
1.2. Terminology 1.2. Terminology
Station (STA): A device that contains an IEEE 802.11 conformant Station (STA): A device that contains an IEEE 802.11-conformant
medium access control (MAC) and physical layer (PHY) interface to the Medium Access Control (MAC) and Physical layer (PHY) interface to the
wireless medium (WM). Wireless Medium (WM).
Access Controller (AC): The network entity that provides WTP access Access Controller (AC): The network entity that provides WTP access
to the network infrastructure in the data plane, control plane, to the network infrastructure in the data plane, control plane,
management plane, or a combination therein. management plane, or a combination therein.
Access Router (AR): A specialized router usually residing at the edge Access Router (AR): A specialized router usually residing at the edge
or boundary of a network. This router ensures the connectivity of or boundary of a network. This router ensures the connectivity of
its network with external networks, a wide area network or the its network with external networks, a wide area network, or the
Internet. Internet.
Wireless Termination Point (WTP): The physical or network entity that Wireless Termination Point (WTP): The physical or network entity that
contains an RF antenna and wireless Physical Layer (PHY) to transmit contains a Radio Frequency (RF) antenna and wireless Physical layer
and receive station traffic for wireless access networks. (PHY) to transmit and receive station traffic for wireless access
networks.
CAPWAP Control Channel: A bi-directional flow defined by the AC IP CAPWAP Control Channel: A bidirectional flow defined by the AC IP
Address, WTP IP Address, AC control port, WTP control port, and the Address, WTP IP Address, AC control port, WTP control port, and the
transport-layer protocol (UDP or UDP-Lite) over which CAPWAP Control transport-layer protocol (UDP or UDP-Lite) over which CAPWAP Control
packets are sent and received. packets are sent and received.
CAPWAP Data Channel: A bi-directional flow defined by the AC IP CAPWAP Data Channel: A bidirectional flow defined by the AC IP
Address, WTP IP Address, AC data port, WTP data port, and the Address, WTP IP Address, AC data port, WTP data port, and the
transport-layer protocol (UDP or UDP-Lite) over which CAPWAP Data transport-layer protocol (UDP or UDP-Lite) over which CAPWAP Data
packets are sent and received. In certain WTP modes, the CAPWAP Data packets are sent and received. In certain WTP modes, the CAPWAP Data
Channel only transports IEEE 802.11 management frames and not the Channel only transports IEEE 802.11 management frames and not the
data plane (user traffic). data plane (user traffic).
1.3. History of the document 1.3. History of the Document
This document was started to accommodate Service Providers' need of a This document was started to accommodate Service Providers' need of a
more flexible deployment mode with alternative tunnels [RFC7494]. more flexible deployment mode with alternative tunnels [RFC7494].
Experiments and tests have been done for this alt-tunnel network Experiments and tests have been done for this alternate tunnel
infrastructure. However important, the deployment of relevant network infrastructure. However important, the deployment of
technology is yet to complete. This experimental document is relevant technology is yet to be completed. This Experimental
intended to serve as an archival record for any future work as to the document is intended to serve as an archival record for any future
operational and deployment requirements. work on the operational and deployment requirements.
2. Alternate Tunnel Encapsulation Overview 2. Alternate Tunnel Encapsulation Overview
+-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+
| WTP | | AC | | WTP | | AC |
+-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+
|Join Request [ Supported Alternate | |Join Request [ Supported Alternate |
| Tunnel Encapsulations ] | | Tunnel Encapsulations ] |
|---------------------------------------->| |---------------------------------------->|
| | | |
|Join Response | |Join Response |
|<----------------------------------------| |<----------------------------------------|
| | | |
skipping to change at page 9, line 32 skipping to change at page 9, line 35
+-+-+-+-+-+-+ | +-+-+-+-+-+-+ |
| Setup | | | Setup | |
| Alternate | | | Alternate | |
| Tunnel | | | Tunnel | |
+-+-+-+-+-+-+ | +-+-+-+-+-+-+ |
|IEEE 802.11 WLAN Configuration Response | |IEEE 802.11 WLAN Configuration Response |
|[ Alternate Tunnel Encapsulation ( | |[ Alternate Tunnel Encapsulation ( |
| Tunnel Type, Tunnel Info Element) ] | | Tunnel Type, Tunnel Info Element) ] |
|---------------------------------------->| |---------------------------------------->|
| | | |
| |
+-+-+-+-+-+-+ | +-+-+-+-+-+-+ |
| Tunnel | | | Tunnel | |
| Failure | | | Failure | |
+-+-+-+-+-+-+ | +-+-+-+-+-+-+ |
|WTP Alternate Tunnel Failure Indication | |WTP Alternate Tunnel Failure Indication |
|(report failure (AR address(es))) | |(Report Failure (AR Address(es))) |
|---------------------------------------->| |---------------------------------------->|
| | | |
+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+ |
| Tunnel | | | Tunnel | |
| Established | | | Established | |
+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+ |
|WTP Alternate Tunnel Failure Indication | |WTP Alternate Tunnel Failure Indication |
|(report clearing failure) | |(Report Clearing Failure) |
|---------------------------------------->| |---------------------------------------->|
| | | |
Figure 5: Setup of Alternate Tunnel Figure 5: Setup of an Alternate Tunnel
The above example describes how the alternate tunnel encapsulation The above example describes how the alternate tunnel encapsulation
may be established. When the WTP joins the AC, it should indicate may be established. When the WTP joins the AC, it should indicate
its alternate tunnel encapsulation capability. The AC determines its alternate tunnel encapsulation capability. The AC determines
whether an alternate tunnel configuration is required. If an whether an alternate tunnel configuration is required. If an
appropriate alternate tunnel type is selected, then the AC provides appropriate alternate tunnel type is selected, then the AC provides
the alternate tunnel encapsulation message element containing the the Alternate Tunnel Encapsulations Type message element containing
tunnel type and a tunnel-specific information element. The tunnel- the tunnel type and a tunnel-specific information element. The
specific information element, for example, may contain information tunnel-specific information element, for example, may contain
like the IP address of the tunnel termination point. The WTP sets up information like the IP address of the tunnel termination point. The
the alternate tunnel using the alternate tunnel encapsulation message WTP sets up the alternate tunnel using the Alternate Tunnel
element. Encapsulations Type message element.
Since AC can configure a WTP with more than one AR available for the Since an AC can configure a WTP with more than one AR available for
WTP to establish the data tunnel(s) for user traffic, it may be the WTP to establish the data tunnel(s) for user traffic, it may be
useful for the WTP to communicate the selected AR. To enable this, useful for the WTP to communicate the selected AR. To enable this,
the IEEE 802.11 WLAN Configuration Response may carry the alternate the IEEE 802.11 WLAN Configuration Response may carry the Alternate
tunnel encapsulation message element containing the AR list element Tunnel Encapsulations Type message element containing the AR list
corresponding to the selected AR as shown in Figure 5. element corresponding to the selected AR as shown in Figure 5.
On detecting a tunnel failure, WTP SHALL forward data frames to the On detecting a tunnel failure, the WTP SHALL forward data frames to
AC and discard the frames. In addition, WTP may dissociate existing the AC and discard the frames. In addition, the WTP may dissociate
clients and refuse association requests from new clients. Depending existing clients and refuse association requests from new clients.
on the implementation and deployment scenario, the AC may choose to Depending on the implementation and deployment scenario, the AC may
reconfigure the WLAN (on the WTP) to a local bridging mode or to choose to reconfigure the WLAN (on the WTP) to a Local Bridging mode
tunnel frames to the AC. When the WTP detects an alternate tunnel or to tunnel frames to the AC. When the WTP detects an alternate
failure, the WTP informs the AC using a message element, WTP tunnel failure, the WTP informs the AC using a message element, IEEE
Alternate Tunnel Fail Indication (defined in this specification). It 802.11 WTP Alternate Tunnel Failure Indication (defined in
MAY be carried in the WTP Event Request message which is defined in Section 3.3). It MAY be carried in the WTP Event Request message,
[RFC5415]. which is defined in [RFC5415].
The WTP also needs to notify the AC of which AR(s) are unavailable. The WTP also needs to notify the AC of which AR(s) are unavailable.
Particularly, in the VNO scenario, the AC of the WLAN service Particularly, in the VNO scenario, the AC of the WLAN service
provider needs to maintain the association of the AR addresses of the provider needs to maintain the association of the AR addresses of the
VNOs and SSIDs, and provide this information to the WTP for the VNOs and SSIDs and provide this information to the WTP for the
purpose of load balancing or master-slave mode. purpose of load balancing or master-slave mode.
The message element has a status field that indicates whether the The message element has a Status field that indicates whether the
message denotes reporting a failure or the clearing of the previously message is reporting a failure or clearing the previously reported
reported failure. failure.
For the case where AC is unreachable but the tunnel end point is For the case where an AC is unreachable but the tunnel endpoint is
still reachable, the WTP behavior is up to the implementation. For still reachable, the WTP behavior is up to the implementation. For
example, the WTP could either choose to tear down the alternate example, the WTP could choose to either tear down the alternate
tunnel or let the existing user's traffic continue to be tunneled. tunnel or let the existing user's traffic continue to be tunneled.
3. CAPWAP Protocol Message Elements Extensions 3. Extensions for CAPWAP Protocol Message Elements
3.1. Supported Alternate Tunnel Encapsulations 3.1. Supported Alternate Tunnel Encapsulations
This message element is sent by a WTP to communicate its capability This message element is sent by a WTP to communicate its capability
to support alternate tunnel encapsulations. The message element to support alternate tunnel encapsulations. The message element
contains the following fields: contains the following fields:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type 1 | Tunnel-Type 2 | | Tunnel-Type 1 | Tunnel-Type 2 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ... | Tunnel-Type N | | ... | Tunnel-Type N |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Supported Alternate Tunnel Encapsulations Figure 6: Supported Alternate Tunnel Encapsulations
o Type: <IANA-1> for Supported Alternate Tunnel Encapsulations o Type: 54 for Supported Alternate Tunnel Encapsulations Type
o Length: The length in bytes, two bytes for each Alternative tunnel
type that is included o Length: The length in bytes; two bytes for each Alternative
o Tunnel-Type: This is identified by value defined in Section 3.2. Tunnel-Type that is included
There may be one or more Tunnel-Types as shows in Figure 6.
o Tunnel-Type: This is identified by the value defined in
Section 3.2. There may be one or more Tunnel-Types, as is shown
in Figure 6.
3.2. Alternate Tunnel Encapsulations Type 3.2. Alternate Tunnel Encapsulations Type
This message element can be sent by the AC. This message element This message element can be sent by the AC, allows the AC to select
allows the AC to select the alternate tunnel encapsulation. This the alternate tunnel encapsulation, and may be provided along with
message element may be provided along with the IEEE 802.11 Add WLAN the IEEE 802.11 Add WLAN message element. When the message element
message element. When the message element is present, the following is present, the following fields of the IEEE 802.11 Add WLAN element
fields of the IEEE 802.11 Add WLAN element SHALL be set as follows: SHALL be set as follows: MAC mode is set to 0 (Local MAC), and Tunnel
MAC mode is set to 0 (Local MAC) and Tunnel Mode is set to 0 (Local Mode is set to 0 (Local Bridging). Besides, the message element can
Bridging). Besides, the message element can also be sent by the WTP also be sent by the WTP to communicate the selected AR(s).
to communicate the selected AR(s).
The message element contains the following fields: The message element contains the following fields:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type | Info Element Length | | Tunnel-Type | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Info Element | Info Element
+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+
Figure 7: Alternate Tunnel Encapsulations Type Figure 7: Alternate Tunnel Encapsulations Type
o Type: <IANA-2> for Alternate Tunnel Encapsulation Type o Type: 55 for Alternate Tunnel Encapsulations Type
o Length: > 4 o Length: > 4
o Tunnel-Type: The tunnel type is specified by a 2 byte value. This
specification defines the values from zero (0) to six (6) as given
below. The remaining values are reserved for future use.
* 0: CAPWAP. This refers to a CAPWAP data channel described in o Tunnel-Type: The Tunnel-Type is specified by a 2-byte value. This
specification defines the values from 0 to 6 as given below. The
remaining values are reserved for future use.
* 0: CAPWAP. This refers to a CAPWAP Data Channel described in
[RFC5415] and [RFC5416]. [RFC5415] and [RFC5416].
* 1: L2TP. This refers to tunnel encapsulation described in * 1: L2TP. This refers to tunnel encapsulation described in
[RFC2661]. [RFC2661].
* 2: L2TPv3. This refers to tunnel encapsulation described in * 2: L2TPv3. This refers to tunnel encapsulation described in
[RFC3931]. [RFC3931].
* 3: IP-in-IP. This refers to tunnel encapsulation described in * 3: IP-in-IP. This refers to tunnel encapsulation described in
[RFC2003]. [RFC2003].
* 4: PMIPv6-UDP. This refers to the UDP encapsulation mode
described in [RFC5844]. This encapsulation mode is the basic * 4: PMIPv6-UDP. This refers to the UDP encapsulation mode for
encapsulation mode and does not include the TLV header Proxy Mobile IPv6 (PMIPv6) described in [RFC5844]. This
specified in section 7.2, of [RFC5845]. encapsulation mode is the basic encapsulation mode and does not
include the TLV header specified in Section 7.2 of [RFC5845].
* 5: GRE. This refers to GRE tunnel encapsulation as described * 5: GRE. This refers to GRE tunnel encapsulation as described
in [RFC2784]. in [RFC2784].
* 6: GTPv1-U. This refers to GTPv1 user plane mode as described
in [TS29281]. * 6: GTPv1-U. This refers to the GPRS Tunnelling Protocol (GTP)
o Info Element: This field contains tunnel specific configuration User Plane mode as described in [TS.3GPP.29.281].
parameters to enable the WTP to setup the alternate tunnel. This
specification provides details for this elements for CAPWAP, o Info Element: This field contains tunnel-specific configuration
parameters to enable the WTP to set up the alternate tunnel. This
specification provides details for this element for CAPWAP,
PMIPv6, and GRE. This specification reserves the tunnel type PMIPv6, and GRE. This specification reserves the tunnel type
values for the key tunnel types and defines the most common values for the key tunnel types and defines the most common
message elements. It is anticipated that message elements for the message elements. It is anticipated that message elements for the
other protocols (like L2TPv3, etc.) will be defined in other other protocols (like L2TPv3) will be defined in other
specifications in the future. specifications in the future.
3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication 3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication
The WTP MAY include the Alternate Tunnel Failure Indication message The WTP MAY include the Alternate Tunnel Failure Indication message
in a WTP Event Request message to inform the AC about the status of in a WTP Event Request message to inform the AC about the status of
the Alternate Tunnel. For the case where WTP establishes data the alternate tunnel. For the case where the WTP establishes data
tunnels with multiple ARs (e.g., under VNO scenario), the WTP needs tunnels with multiple ARs (e.g., under a VNO scenario), the WTP needs
to notify the AC of which AR(s) are unavailable. The message element to notify the AC of which AR(s) are unavailable. The message element
contains the following fields: contains the following fields:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| WLAN ID | Status | Reserved | | WLAN ID | Status | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element . . Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: IEEE 802.11 WTP Alternate Tunnel Failure Indication Figure 8: IEEE 802.11 WTP Alternate Tunnel Failure Indication
o Type: <IANA-3> for IEEE 802.11 WTP Alternate Tunnel Failure o Type: 1062 for IEEE 802.11 WTP Alternate Tunnel Failure Indication
Indication
o Length: > 4 o Length: > 4
o WLAN ID: An 8-bit value specifying the WLAN Identifier. The value o WLAN ID: An 8-bit value specifying the WLAN Identifier. The value
MUST be between one (1) and 16. MUST be between 1 and 16.
o Status: An 8-bit boolean indicating whether the radio failure is o Status: An 8-bit boolean indicating whether the radio failure is
being reported or cleared. A value of zero is used to clear the being reported or cleared. A value of 0 is used to clear the
event, while a value of one is used to report the event. event, while a value of 1 is used to report the event.
o Reserved: MUST be set to a value of 0 and MUST be ignored by the o Reserved: MUST be set to a value of 0 and MUST be ignored by the
receiver. receiver.
o Access Router Information Element: IPv4 address or IPv6 address of
the Access Router that terminates the alternate tunnel. The o Access Router Information Element: The IPv4 or IPv6 address of the
Access Router Information Elements allow the WTP to notify the AC Access Router that terminates the alternate tunnel. The Access
of which AR(s) are unavailable. Router Information Elements allow the WTP to notify the AC of
which AR(s) are unavailable.
4. Alternate Tunnel Types 4. Alternate Tunnel Types
4.1. CAPWAP based Alternate Tunnel 4.1. CAPWAP-Based Alternate Tunnel
If the CAPWAP encapsulation is selected by the AC and configured by If the CAPWAP encapsulation is selected by the AC and configured by
the AC to the WTP, the Info Element field defined in Section 3.2 the AC to the WTP, the Info Element field defined in Section 3.2
SHOULD contain the following information: SHOULD contain the following information:
o Access Router Information: IPv4 address or IPv6 address of the o Access Router Information: The IPv4 or IPv6 address of the Access
Access Router for the alternate tunnel. Router for the alternate tunnel.
o Tunnel DTLS Policy: The CAPWAP protocol allows optional protection o Tunnel DTLS Policy: The CAPWAP protocol allows optional protection
of data packets using DTLS. Use of data packet protection on a of data packets using DTLS. Use of data packet protection on a
WTP is not mandatory but determined by the associated AC policy WTP is not mandatory but is determined by the associated AC
(This is consistent with the WTP behavior described in [RFC5415]). policy. (This is consistent with the WTP behavior described in
[RFC5415].)
o IEEE 802.11 Tagging Mode Policy: It is used to specify how the o IEEE 802.11 Tagging Mode Policy: It is used to specify how the
CAPWAP data channel packet are to be tagged for QoS purposes (see CAPWAP Data Channel packets are to be tagged for QoS purposes (see
[RFC5416] for more details). [RFC5416] for more details).
o CAPWAP Transport Protocol: The CAPWAP protocol supports both UDP o CAPWAP Transport Protocol: The CAPWAP protocol supports both UDP
and UDP-Lite (see [RFC3828]). When run over IPv4, UDP is used for and UDP-Lite (see [RFC3828]). When run over IPv4, UDP is used for
the CAPWAP data channels. When run over IPv6, the CAPWAP data the CAPWAP Data Channels. When run over IPv6, the CAPWAP Data
channel may use either UDP or UDP-lite. Channel may use either UDP or UDP-Lite.
The message element structure for CAPWAP encapsulation is shown in The message element structure for CAPWAP encapsulation is shown in
Figure 9: Figure 9:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type=0 | Info Element Length | | Tunnel-Type=0 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element . . Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Tunnel DTLS Policy Element . . Tunnel DTLS Policy Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. IEEE 802.11 Tagging Mode Policy Element . . IEEE 802.11 Tagging Mode Policy Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. CAPWAP Transport Protocol Element . . CAPWAP Transport Protocol Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Alternate Tunnel Encapsulation - CAPWAP Figure 9: Alternate Tunnel Encapsulation - CAPWAP
4.2. PMIPv6 based Alternate Tunnel 4.2. PMIPv6-Based Alternate Tunnel
Proxy Mobile IPv6 (PMIPv6) (defined in [RFC5213]) based user plane A user plane based on PMIPv6 (defined in [RFC5213]) can also be used
can also be used as alternate tunnel encapsulation between the WTP as an alternate tunnel encapsulation between the WTP and the AR. In
and the AR. In this scenario, a WTP acts as the Mobile Access this scenario, a WTP acts as the Mobile Access Gateway (MAG) function
Gateway (MAG) function that manages the mobility-related signaling that manages the mobility-related signaling for a station that is
for a station that is attached to the WTP IEEE 802.11 radio access. attached to the WTP IEEE 802.11 radio access. The Local Mobility
The Local Mobility Anchor (LMA) function is at the AR. If PMIPv6 UDP Anchor (LMA) function is at the AR. If PMIPv6 UDP encapsulation is
encapsulation is selected by the AC and configured by the AC to a selected by the AC and configured by the AC to a WTP, the Info
WTP, the Info Element field defined in Section 3.2 SHOULD contain the Element field defined in Section 3.2 SHOULD contain the following
following information: information:
o Access Router (acting as LMA) Information: IPv4 or IPv6 address o Access Router (acting as LMA) Information: IPv4 or IPv6 address
for the alternate tunnel endpoint. for the alternate tunnel endpoint.
The message element structure for PMIPv6 encapsulation is shown in The message element structure for PMIPv6 encapsulation is shown in
Figure 10: Figure 10:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type=4 | Info Element Length | | Tunnel-Type=4 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element . . Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: Alternate Tunnel Encapsulation - PMIPv6 Figure 10: Alternate Tunnel Encapsulation - PMIPv6
4.3. GRE based Alternate Tunnel 4.3. GRE-Based Alternate Tunnel
Generic Routing Encapsulation (defined in [RFC2784]) mode based user A user plane based on Generic Routing Encapsulation (defined in
plane can also be used as alternate tunnel encapsulation between the [RFC2784]) can also be used as an alternate tunnel encapsulation
WTP and the AR. In this scenario, a WTP and the access router between the WTP and the AR. In this scenario, a WTP and the Access
represent the two end points of the GRE tunnel. If GRE encapsulation Router represent the two endpoints of the GRE tunnel. If GRE is
is selected by the AC and configured by the AC to a WTP, the Info selected by the AC and configured by the AC to a WTP, the Info
Element field defined in Section 3.2 SHOULD contain the following Element field defined in Section 3.2 SHOULD contain the following
information: information:
o Access Router Information: IPv4 or IPv6 address for the alternate o Access Router Information: The IPv4 or IPv6 address for the
tunnel endpoint. alternate tunnel endpoint.
o GRE Key Information: The Key field is intended to be used for o GRE Key Information: The Key field is intended to be used for
identifying an individual traffic flow within a tunnel [RFC2890]. identifying an individual traffic flow within a tunnel [RFC2890].
The message element structure for GRE encapsulation is shown in The message element structure for GRE is shown in Figure 11:
Figure 11:
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type=5 | Info Element Length | | Tunnel-Type=5 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Element . . Access Router Information Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. GRE Key Element . . GRE Key Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: Alternate Tunnel Encapsulation - GRE Figure 11: Alternate Tunnel Encapsulation - GRE
5. Alternate Tunnel Information Elements 5. Alternate Tunnel Information Elements
This section defines the various elements described in Section 4.1, This section defines the various elements described in Sections 4.1,
Section 4.2, and Section 4.3. 4.2, and 4.3.
These information elements can only be included in the Alternate These information elements can only be included in the Alternate
Tunnel Encapsulations Type message element, and the IEEE 802.11 WTP Tunnel Encapsulations Type message element and the IEEE 802.11 WTP
Alternate Tunnel Failure Indication message element as their sub- Alternate Tunnel Failure Indication message element as their sub-
elements. elements.
5.1. Access Router Information Elements 5.1. Access Router Information Elements
The Access Router Information Elements allow the AC to notify a WTP The Access Router Information Elements allow the AC to notify a WTP
of which AR(s) are available for establishing a data tunnel. The AR of which AR(s) are available for establishing a data tunnel. The AR
information may be IPv4 address, or IPv6 address.This information information may be an IPv4 or IPv6 address. For any Tunnel-Type,
element SHOULD be contained whatever the tunnel type is. this information element SHOULD be included in the Alternate Tunnel
Encapsulations Type message element.
If the Alternate Tunnel Encapsulations Type message element is sent If the Alternate Tunnel Encapsulations Type message element is sent
by the WTP to communicate the selected AR(s), this Access Router by the WTP to communicate the selected AR(s), this Access Router
Information Element SHOULD be contained. Information Element SHOULD be included in it.
The following are the Access Router Information Elements defined in The following are the Access Router Information Elements defined in
this specification. The AC can use one of them to notify the this specification. The AC can use one of them to notify the WTP
destination information of the data tunnel to the WTP. The Elements about the destination information of the data tunnel. The Elements
containing the AR IPv4 address MUST NOT be used if an IPv6 data containing the AR IPv4 address MUST NOT be used if an IPv6 Data
channel with IPv6 transport is used. Channel with IPv6 transport is used.
5.1.1. AR IPv4 List Element 5.1.1. AR IPv4 List Element
This Element (see Figure 12) is used by the AC to configure a WTP This element (see Figure 12) is used by the AC to configure a WTP
with the AR IPv4 address available for the WTP to establish the data with the AR IPv4 address available for the WTP to establish the data
tunnel for user traffic. tunnel for user traffic.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AR IPv4 Element Type | Length | | AR IPv4 Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-1 . . AR IPv4 Address-1 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-2 . . AR IPv4 Address-2 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-N . . AR IPv4 Address-N .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: AR IPv4 List Element Figure 12: AR IPv4 List Element
Type: 0 Type: 0
Length: This refers to the total length in octets of the element Length: This refers to the total length in octets of the element,
excluding the Type and Length fields. excluding the Type and Length fields.
AR IPv4 Address: The IPv4 address of the AR. At least one IPv4 AR IPv4 Address: The IPv4 address of the AR. At least one IPv4
address SHALL be present. Multiple addresses may be provided for address SHALL be present. Multiple addresses may be provided for
load balancing or redundancy. load balancing or redundancy.
5.1.2. AR IPv6 List Element 5.1.2. AR IPv6 List Element
This Element (see Figure 13) is used by the AC to configure a WTP This element (see Figure 13) is used by the AC to configure a WTP
with the AR IPv6 address available for the WTP to establish the data with the AR IPv6 address available for the WTP to establish the data
tunnel for user traffic. tunnel for user traffic.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AR IPv6 Element Type | Length | | AR IPv6 Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address-1 . . AR IPv6 Address-1 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 17, line 30 skipping to change at page 17, line 45
Length: This refers to the total length in octets of the element Length: This refers to the total length in octets of the element
excluding the Type and Length fields. excluding the Type and Length fields.
AR IPv6 Address: The IPv6 address of the AR. At least one IPv6 AR IPv6 Address: The IPv6 address of the AR. At least one IPv6
address SHALL be present. Multiple addresses may be provided for address SHALL be present. Multiple addresses may be provided for
load balancing or redundancy. load balancing or redundancy.
5.2. Tunnel DTLS Policy Element 5.2. Tunnel DTLS Policy Element
The AC distributes its DTLS usage policy for the CAPWAP data tunnel The AC distributes its Datagram Transport Layer Security (DTLS) usage
between a WTP and the AR. There are multiple supported options, policy for the CAPWAP data tunnel between a WTP and the AR. There
represented by the bit field below as defined in AC Descriptor are multiple supported options, which are represented by the bit
message elements. The WTP MUST abide by one of the options for fields below as defined in AC Descriptor message elements. The WTP
tunneling user traffic with AR. The Tunnel DTLS Policy Element obeys MUST abide by one of the options for tunneling user traffic with AR.
the definition in [RFC5415]. If, for reliability reasons, the AC has The Tunnel DTLS Policy Element obeys the definition in [RFC5415].
provided more than one AR address in the Access Router Information If, for reliability reasons, the AC has provided more than one AR
Element, the same Tunnel DTLS Policy (the last one in Figure 14) is address in the Access Router Information Element, the same Tunnel
generally applied for all tunnels associated with those ARs. DTLS Policy (the last one in Figure 14) is generally applied for all
Otherwise, Tunnel DTLS Policy MUST be bonded together with each of tunnels associated with those ARs. Otherwise, Tunnel DTLS Policy
the Access Router Information Elements, and the WTP will enforce the MUST be bonded together with each of the Access Router Information
independent tunnel DTLS policy for each tunnel with a specific AR. Elements, and the WTP will enforce the independent tunnel DTLS policy
for each tunnel with a specific AR.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Tunnel DTLS Policy Element Type| Length | |Tunnel DTLS Policy Element Type| Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |D|C|R| | Reserved |D|C|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information . . AR Information .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 18, line 31 skipping to change at page 18, line 36
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: Tunnel DTLS Policy Element Figure 14: Tunnel DTLS Policy Element
Type: 2 Type: 2
Length: This refers to the total length in octets of the element Length: This refers to the total length in octets of the element
excluding the Type and Length fields. excluding the Type and Length fields.
Reserved: A set of reserved bits for future use. All implementations Reserved: A set of reserved bits for future use. All implementations
complying with this protocol MUST set to zero any bits that are complying with this protocol MUST set to 0 any bits that are reserved
reserved in the version of the protocol supported by that in the version of the protocol supported by that implementation.
implementation. Receivers MUST ignore all bits not defined for the Receivers MUST ignore all bits not defined for the version of the
version of the protocol they support. protocol they support.
D: DTLS-Enabled Data Channel Supported (see [RFC5415]). D: DTLS-Enabled Data Channel Supported (see [RFC5415]).
C: Clear Text Data Channel Supported (see [RFC5415]). C: Clear Text Data Channel Supported (see [RFC5415]).
R: A reserved bit for future use (see [RFC5415]). R: A reserved bit for future use (see [RFC5415]).
AR Information: This means Access Router Information Element. In AR Information: This means Access Router Information Element. In
this context, each address in AR information MUST be one of this context, each address in AR Information MUST be one of
previously specified AR addresses. previously specified AR addresses.
The last element having no AR Information in Figure 14 is the default In Figure 14, the last element that has no AR Information is the
tunnel DTLS policy, and provides options for any address not default tunnel DTLS policy, which provides options for any address
previously mentioned. Therefore, the AR information field here is not previously mentioned. Therefore, the AR Information field here
optional. If all ARs share the same tunnel DTLS policy, in this is optional. In this element, if all ARs share the same tunnel DTLS
element, there will not be AR information field and its specific policy, there won't be an AR Information field or its specific tunnel
tunnel DTLS policy. DTLS policy.
5.3. IEEE 802.11 Tagging Mode Policy Element 5.3. IEEE 802.11 Tagging Mode Policy Element
In 802.11 networks, IEEE 802.11 Tagging Mode Policy Element is used In IEEE 802.11 networks, the IEEE 802.11 Tagging Mode Policy Element
to specify how the WTP applies the QoS tagging policy when receiving is used to specify how the WTP applies the QoS tagging policy when
the packets from stations on a particular radio. When the WTP sends receiving the packets from stations on a particular radio. When the
out the packet to data channel to the AR(s), the packets have to be WTP sends out the packet to data channel to the AR(s), the packets
tagged for QoS purposes (see [RFC5416]). have to be tagged for QoS purposes (see [RFC5416]).
The IEEE 802.11 Tagging Mode Policy abides the IEEE 802.11 WTP The IEEE 802.11 Tagging Mode Policy abides by the IEEE 802.11 WTP
Quality of Service defined in Section 6.22 of [RFC5416]. Quality of Service defined in Section 6.22 of [RFC5416].
If, for reliability reasons, the AC has provided more than one AR If, for reliability reasons, the AC has provided more than one AR
address in the Access Router Information Element, the same IEEE address in the Access Router Information Element, the same IEEE
802.11 Tagging Mode Policy (the last one in Figure 15) is generally 802.11 Tagging Mode Policy (the last one in Figure 15) is generally
applied for all tunnels associated with those ARs. Otherwise, IEEE applied for all tunnels associated with those ARs. Otherwise, IEEE
802.11 Tagging Mode Policy MUST be bonded together with each of the 802.11 Tagging Mode Policy MUST be bonded together with each of the
Access Router Information Elements, and the WTP will enforce the Access Router Information Elements, and the WTP will enforce the
independent IEEE 802.11 Tagging Mode Policy for each tunnel with a independent IEEE 802.11 Tagging Mode Policy for each tunnel with a
specific AR. specific AR.
skipping to change at page 20, line 5 skipping to change at page 20, line 12
Figure 15: IEEE 802.11 Tagging Mode Policy Element Figure 15: IEEE 802.11 Tagging Mode Policy Element
Type: 3 Type: 3
Length: This refers to the total length in octets of the element Length: This refers to the total length in octets of the element
excluding the Type and Length fields. excluding the Type and Length fields.
Reserved: A set of reserved bits for future use. Reserved: A set of reserved bits for future use.
P: When set, the WTP is to employ the 802.1p QoS mechanism (see P: When set, the WTP is to employ the IEEE 802.1p QoS mechanism (see
[RFC5416]). [RFC5416]).
Q: When the 'P' bit is set, the 'Q' bit is used by the AC to Q: When the 'P' bit is set, the 'Q' bit is used by the AC to
communicate to the WTP how 802.1p QoS is to be enforced (see communicate to the WTP how IEEE 802.1p QoS is to be enforced (see
[RFC5416]). [RFC5416]).
D: When set, the WTP is to employ the DSCP QoS mechanism (see D: When set, the WTP is to employ the DSCP QoS mechanism (see
[RFC5416]). [RFC5416]).
O: When the 'D' bit is set, the 'O' bit is used by the AC to O: When the 'D' bit is set, the 'O' bit is used by the AC to
communicate to the WTP how DSCP QoS is to be enforced on the outer communicate to the WTP how Differentiated Services Code Point (DSCP)
(tunneled) header (see [RFC5416]). QoS is to be enforced on the outer (tunneled) header (see [RFC5416]).
I: When the 'D' bit is set, the 'I' bit is used by the AC to I: When the 'D' bit is set, the 'I' bit is used by the AC to
communicate to the WTP how DSCP QoS is to be enforced on the communicate to the WTP how DSCP QoS is to be enforced on the
station's packet (inner) header (see [RFC5416]). station's packet (inner) header (see [RFC5416]).
AR Information: This means Access Router Information Element. In AR Information: This means Access Router Information Element. In
this context, each address in AR information MUST be one of this context, each address in AR information MUST be one of the
previously specified AR addresses. previously specified AR addresses.
The last element having no AR Information in Figure 15 is the default In Figure 15, the last element that has no AR information is the
IEEE 802.11 Tagging Mode Policy, and provides options for any address default IEEE 802.11 Tagging Mode Policy, which provides options for
not previously mentioned. Therefore, the AR information field here any address not previously mentioned. Therefore, the AR Information
is optional. If all ARs share the same IEEE 802.11 Tagging Mode field here is optional. If all ARs share the same IEEE 802.11
Policy, in this element, there will not be AR information field and Tagging Mode Policy, in this element, there will not be an AR
its specific IEEE 802.11 Tagging Mode Policy. Information field and its specific IEEE 802.11 Tagging Mode Policy.
5.4. CAPWAP Transport Protocol Element 5.4. CAPWAP Transport Protocol Element
The CAPWAP data tunnel supports both UDP and UDP-Lite (see The CAPWAP data tunnel supports both UDP and UDP-Lite (see
[RFC3828]). When run over IPv4, UDP is used for the CAPWAP data [RFC3828]). When run over IPv4, UDP is used for the CAPWAP Data
channels. When run over IPv6, the CAPWAP data channel may use either Channels. When run over IPv6, the CAPWAP Data Channel may use either
UDP or UDP-lite. The AC specifies and configures the WTP for which UDP or UDP-Lite. The AC specifies and configures the WTP for which
transport protocol is to be used for the CAPWAP data tunnel. the transport protocol is to be used for the CAPWAP data tunnel.
The CAPWAP Transport Protocol Element abides the definition in The CAPWAP Transport Protocol Element abides by the definition in
Section 4.6.14 of [RFC5415]. Section 4.6.14 of [RFC5415].
If, for reliability reasons, the AC has provided more than one AR If, for reliability reasons, the AC has provided more than one AR
address in the Access Router Information Element, the same CAPWAP address in the Access Router Information Element, the same CAPWAP
Transport Protocol (the last one in Figure 16) is generally applied Transport Protocol (the last one in Figure 16) is generally applied
for all tunnels associated with those ARs. Otherwise, CAPWAP for all tunnels associated with those ARs. Otherwise, CAPWAP
Transport Protocol MUST be bonded together with each of the Access Transport Protocol MUST be bonded together with each of the Access
Router Information Elements, and the WTP will enforce the independent Router Information Elements, and the WTP will enforce the independent
CAPWAP Transport Protocol for each tunnel with a specific AR. CAPWAP Transport Protocol for each tunnel with a specific AR.
skipping to change at page 21, line 29 skipping to change at page 21, line 37
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transport | Reserved | | Transport | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: CAPWAP Transport Protocol Element Figure 16: CAPWAP Transport Protocol Element
Type: 4 Type: 4
Length: 1 Length: 1
Transport: The transport to use for the CAPWAP Data channel. The Transport: The transport to use for the CAPWAP Data Channel. The
following enumerated values are supported: following enumerated values are supported:
1 - UDP-Lite: The UDP-Lite transport protocol is to be used for the 1 - UDP-Lite: The UDP-Lite transport protocol is to be used for
CAPWAP Data channel. Note that this option MUST NOT be used if the the CAPWAP Data Channel. Note that this option MUST NOT be used
CAPWAP Control channel is being used over IPv4 and AR address is IPv4 if the CAPWAP Control Channel is being used over IPv4 and if the
contained in the AR Information Element. AR address contained in the AR Information Element is an IPv4
address.
2 - UDP: The UDP transport protocol is to be used for the CAPWAP Data 2 - UDP: The UDP transport protocol is to be used for the CAPWAP
channel. Data Channel.
AR Information: This means Access Router Information Element. In AR Information: This means Access Router Information Element. In
this context, each address in AR information MUST be one of this context, each address in AR information MUST be one of the
previously specified AR addresses. previously specified AR addresses.
The last element having no AR Information in Figure 16 is the default In Figure 16, the last element that has no AR information is the
CAPWAP Transport Protocol, and provides options for any address not default CAPWAP Transport Protocol, which provides options for any
previously mentioned. Therefore, the AR information field here is address not previously mentioned. Therefore, the AR Information
optional. If all ARs share the same CAPWAP Transport Protocol, in field here is optional. If all ARs share the same CAPWAP Transport
this element, there will not be AR information field and its specific Protocol, in this element, there will not be an AR Information field
CAPWAP Transport Protocol. and its specific CAPWAP Transport Protocol.
5.5. GRE Key Element 5.5. GRE Key Element
If a WTP receives the GRE Key Element in the Alternate Tunnel If a WTP receives the GRE Key Element in the Alternate Tunnel
Encapsulation message element for GRE selection, the WTP MUST insert Encapsulations Type message element for GRE selection, the WTP MUST
the GRE Key to the encapsulation packet (see [RFC2890]). An AR insert the GRE Key to the encapsulation packet (see [RFC2890]). An
acting as decapsulating tunnel endpoint identifies packets belonging AR acting as a decapsulating tunnel endpoint identifies packets
to a traffic flow based on the Key value. belonging to a traffic flow based on the Key value.
The GRE Key Element field contains a four octet number defined in The GRE Key Element field contains a 4-octet number defined in
[RFC2890]. [RFC2890].
If, for reliability reasons, the AC has provided more than one AR If, for reliability reasons, the AC has provided more than one AR
address in the Access Router Information Element, a GRE Key Element address in the Access Router Information Element, a GRE Key Element
MAY be bonded together with each of the Access Router Information MAY be bonded together with each of the Access Router Information
Elements, and the WTP will enforce the independent GRE Key for each Elements, and the WTP will enforce the independent GRE Key for each
tunnel with a specific AR. tunnel with a specific AR.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
skipping to change at page 22, line 45 skipping to change at page 23, line 5
. ...... . . ...... .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 17: GRE Key Element Figure 17: GRE Key Element
Type: 5 Type: 5
Length: This refers to the total length in octets of the element Length: This refers to the total length in octets of the element
excluding the Type and Length fields. excluding the Type and Length fields.
GRE Key: The Key field contains a four octet number which is inserted GRE Key: The Key field contains a 4-octet number that is inserted by
by the WTP according to [RFC2890]. the WTP according to [RFC2890].
AR Information: This means Access Router Information Element. In AR Information: This means Access Router Information Element. In
this context, it SHOULD be restricted to a single address, and MUST this context, it SHOULD be restricted to a single address and MUST be
be the address of one of previously specified AR addresses. the address of one of previously specified AR addresses.
Any address not explicitly mentioned here does not have a GRE key. Any address not explicitly mentioned here does not have a GRE key.
5.6. IPv6 MTU Element 5.6. IPv6 MTU Element
If AC has chosen a tunneling mechanism based on IPv6, it SHOULD If AC has chosen a tunneling mechanism based on IPv6, it SHOULD
support the minimum IPv6 MTU requirements [RFC8200]. This issue is support the minimum IPv6 MTU requirements [RFC8200]. This issue is
described in [I-D.ietf-intarea-tunnels]. AC SHOULD inform the WTP described in [ARCH-TUNNELS]. AC SHOULD inform the WTP about the IPv6
about the IPv6 MTU information in the "Tunnel Info Element" field. MTU information in the Tunnel Info Element field.
If, for reliability reasons, the AC has provided more than one AR If, for reliability reasons, the AC has provided more than one AR
address in the Access Router Information Element, an IPv6 MTU Element address in the Access Router Information Element, an IPv6 MTU Element
MAY be bonded together with each of the Access Router Information MAY be bonded together with each of the Access Router Information
Elements, and the WTP will enforce the independent IPv6 MTU for each Elements, and the WTP will enforce the independent IPv6 MTU for each
tunnel with a specific AR. tunnel with a specific AR.
0 1 2 3 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
skipping to change at page 23, line 41 skipping to change at page 23, line 50
| ...... | | ...... |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 18: IPv6 MTU Element Figure 18: IPv6 MTU Element
Type: 6 Type: 6
Length: This refers to the total length in octets of the element Length: This refers to the total length in octets of the element
excluding the Type and Length fields. excluding the Type and Length fields.
Minimum IPv6 MTU: The field contains a two octet number indicate the Minimum IPv6 MTU: The field contains a 2-octet number indicating the
minimum IPv6 MTU in the tunnel. minimum IPv6 MTU in the tunnel.
AR Information: This means Access Router Information Element. In AR Information: This means Access Router Information Element. In
this context, each address in AR information MUST be one of this context, each address in AR information MUST be one of
previously specified AR addresses. previously specified AR addresses.
6. IANA Considerations 6. IANA Considerations
This document requires the following IANA considerations. Per this document, IANA has registered the following values in the
existing "CAPWAP Message Element Type" registry, defined in
[RFC5415].
o <IANA-1>. This specification defines the Supported Alternate o 54: Supported Alternate Tunnel Encapsulations Type as defined in
Tunnel Encapsulations Type message element in Section 3.1. This Section 3.1.
elements needs to be registered in the existing CAPWAP Message
Element Type registry, defined in [RFC5415]. The Type value for
this element needs to be between 1 and 1023 (see Section 15.7 in
[RFC5415]).
o <IANA-2>. This specification defines the Alternate Tunnel
Encapsulations Type message element in Section 3.2. This element
needs to be registered in the existing CAPWAP Message Element Type
registry, defined in [RFC5415]. The Type value for this element
needs to be between 1 and 1023.
o <IANA-3>. This specification defines the IEEE 802.11 WTP
Alternate Tunnel Failure Indication message element in
Section 3.3. This element needs to be registered in the existing
CAPWAP Message Element Type registry, defined in [RFC5415]. The
Type value for this element needs to be between 1024 and 2047.
o Alternate Tunnel-Types Registry: This specification defines the
Alternate Tunnel Encapsulations Type message element. This
element contains a field Tunnel-Type. The namespace for the field
is 16 bits (0-65535). This specification defines values, zero (0)
through six (6) and can be found in Section 3.2. Future
allocations of values in this name space are to be assigned by
IANA using the "Specification Required" policy. IANA needs to
create a registry called CAPWAP Alternate Tunnel-Types. The
registry format is given below.
Tunnel-Type Type Value Reference o 55: Alternate Tunnel Encapsulations Type as defined in
CAPWAP 0 [RFC5415],[RFC5416] Section 3.2.
L2TP 1 [RFC2661]
L2TPv3 2 [RFC3931]
IP-IP 3 [RFC2003]
PMIPv6-UDP 4 [RFC5844]
GRE 5 [RFC2784]
GTPv1-U 6 [3GPP TS 29.281]
o Alternate Tunnel Sub-elements Registry: This specification defines o 1062: IEEE 802.11 WTP Alternate Tunnel Failure Indication as
the Alternate Tunnel Sub-elements. Currently, these information defined in Section 3.3.
elements can only be included in the Alternate Tunnel
Encapsulations Type message element, and the IEEE 802.11 WTP
Alternate Tunnel Failure Indication message element as their sub-
elements. These information elements contains a Type field. The
namespace for the field is 16 bits (0-65535). This specification
defines values, zero (0) through six (6) in Section 5. This
namespace is managed by IANA and assignments require an Expert
Review.
Type Type Value Per this document, IANA has created a registry called "Alternate
Tunnel-Types" under "CAPWAP Parameters". This specification defines
the Alternate Tunnel Encapsulations Type message element. This
element contains a field Tunnel-Type. The namespace for the field is
16 bits (0-65535). This specification defines values 0 through 6 and
can be found in Section 3.2. Future allocations of values in this
namespace are to be assigned by IANA using the "Specification
Required" policy [RFC8126]. The registry format is given below.
Description Value Reference
CAPWAP 0 [RFC5415] [RFC5416]
L2TP 1 [RFC2661]
L2TPv3 2 [RFC3931]
IP-IP 3 [RFC2003]
PMIPv6-UDP 4 [RFC5844]
GRE 5 [RFC2784]
GTPv1-U 6 [TS.3GPP.29.281]
Per this document, IANA has created a registry called "Alternate
Tunnel Sub-elements" under "CAPWAP Parameters". This specification
defines the Alternate Tunnel Sub-elements. Currently, these
information elements can only be included in the Alternate Tunnel
Encapsulations Type message element with the IEEE 802.11 WTP
Alternate Tunnel Failure Indication message element as its sub-
elements. These information elements contain a Type field. The
namespace for the field is 16 bits (0-65535). This specification
defines values 0 through 6 in Section 5. This namespace is managed
by IANA, and assignments require an Expert Review [RFC8126].
Description Value
AR IPv4 List 0 AR IPv4 List 0
AR IPv6 List 1 AR IPv6 List 1
Tunnel DTLS Policy 2 Tunnel DTLS Policy 2
IEEE 802.11 Tagging Mode Policy 3 IEEE 802.11 Tagging Mode Policy 3
CAPWAP Transport Protocol 4 CAPWAP Transport Protocol 4
GRE Key 5 GRE Key 5
IPv6 MTU 6 IPv6 MTU 6
7. Security Considerations 7. Security Considerations
This document introduces three new CAPWAP WTP message elements. This document introduces three new CAPWAP WTP message elements.
These elements are transported within CAPWAP Control messages as the These elements are transported within CAPWAP Control messages as the
existing message elements. Therefore, this document does not existing message elements. Therefore, this document does not
introduce any new security risks to the control plane compared to introduce any new security risks to the control plane compared to
[RFC5415] and [RFC5416]. In the data plane, if the encapsulation [RFC5415] and [RFC5416]. In the data plane, if the encapsulation
type selected itself is not secured, it is suggested to protect the type selected itself is not secured, it is suggested to protect the
tunnel by using known secure methods, such as IPSec. tunnel by using known secure methods, such as IPsec.
8. Contributors
The authors would like to thank Andreas Schultz, Hong Liu, Yifan
Chen, Chunju Shao, Li Xue, Jianjie You, Jin Li, Joe Touch, Alexey
Melnikov, Kathleen Moriarty, Mirja Kuehlewind, Catherine Meadows, and
Paul Kyzivat for their valuable comments.
9. References 8. References
9.1. Normative References 8.1. Normative References
[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003, [RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003,
DOI 10.17487/RFC2003, October 1996, DOI 10.17487/RFC2003, October 1996,
<https://www.rfc-editor.org/info/rfc2003>. <https://www.rfc-editor.org/info/rfc2003>.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997, DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>. <https://www.rfc-editor.org/info/rfc2119>.
skipping to change at page 26, line 31 skipping to change at page 26, line 36
(CAPWAP) Protocol Specification", RFC 5415, (CAPWAP) Protocol Specification", RFC 5415,
DOI 10.17487/RFC5415, March 2009, DOI 10.17487/RFC5415, March 2009,
<https://www.rfc-editor.org/info/rfc5415>. <https://www.rfc-editor.org/info/rfc5415>.
[RFC5416] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley, [RFC5416] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
Ed., "Control and Provisioning of Wireless Access Points Ed., "Control and Provisioning of Wireless Access Points
(CAPWAP) Protocol Binding for IEEE 802.11", RFC 5416, (CAPWAP) Protocol Binding for IEEE 802.11", RFC 5416,
DOI 10.17487/RFC5416, March 2009, DOI 10.17487/RFC5416, March 2009,
<https://www.rfc-editor.org/info/rfc5416>. <https://www.rfc-editor.org/info/rfc5416>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6 [RFC8200] Deering, S. and R. Hinden, "Internet Protocol, Version 6
(IPv6) Specification", STD 86, RFC 8200, (IPv6) Specification", STD 86, RFC 8200,
DOI 10.17487/RFC8200, July 2017, DOI 10.17487/RFC8200, July 2017,
<https://www.rfc-editor.org/info/rfc8200>. <https://www.rfc-editor.org/info/rfc8200>.
9.2. Informative References 8.2. Informative References
[I-D.ietf-intarea-tunnels] [ARCH-TUNNELS]
Touch, J. and M. Townsley, "IP Tunnels in the Internet Touch, J. and M. Townsley, "IP Tunnels in the Internet
Architecture", draft-ietf-intarea-tunnels-08 (work in Architecture", Work in Progress, draft-ietf-intarea-
progress), January 2018. tunnels-08, January 2018.
[RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V., [RFC5213] Gundavelli, S., Ed., Leung, K., Devarapalli, V.,
Chowdhury, K., and B. Patil, "Proxy Mobile IPv6", Chowdhury, K., and B. Patil, "Proxy Mobile IPv6",
RFC 5213, DOI 10.17487/RFC5213, August 2008, RFC 5213, DOI 10.17487/RFC5213, August 2008,
<https://www.rfc-editor.org/info/rfc5213>. <https://www.rfc-editor.org/info/rfc5213>.
[RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy [RFC5844] Wakikawa, R. and S. Gundavelli, "IPv4 Support for Proxy
Mobile IPv6", RFC 5844, DOI 10.17487/RFC5844, May 2010, Mobile IPv6", RFC 5844, DOI 10.17487/RFC5844, May 2010,
<https://www.rfc-editor.org/info/rfc5844>. <https://www.rfc-editor.org/info/rfc5844>.
skipping to change at page 27, line 16 skipping to change at page 27, line 32
"Generic Routing Encapsulation (GRE) Key Option for Proxy "Generic Routing Encapsulation (GRE) Key Option for Proxy
Mobile IPv6", RFC 5845, DOI 10.17487/RFC5845, June 2010, Mobile IPv6", RFC 5845, DOI 10.17487/RFC5845, June 2010,
<https://www.rfc-editor.org/info/rfc5845>. <https://www.rfc-editor.org/info/rfc5845>.
[RFC7494] Shao, C., Deng, H., Pazhyannur, R., Bari, F., Zhang, R., [RFC7494] Shao, C., Deng, H., Pazhyannur, R., Bari, F., Zhang, R.,
and S. Matsushima, "IEEE 802.11 Medium Access Control and S. Matsushima, "IEEE 802.11 Medium Access Control
(MAC) Profile for Control and Provisioning of Wireless (MAC) Profile for Control and Provisioning of Wireless
Access Points (CAPWAP)", RFC 7494, DOI 10.17487/RFC7494, Access Points (CAPWAP)", RFC 7494, DOI 10.17487/RFC7494,
April 2015, <https://www.rfc-editor.org/info/rfc7494>. April 2015, <https://www.rfc-editor.org/info/rfc7494>.
[TS29281] "3rd Generation Partnership Project; Technical [TS.3GPP.29.281]
Specification Group Core Network and Terminals; General 3GPP, "General Packet Radio System (GPRS) Tunnelling
Packet Radio System (GPRS) Tunnelling Protocol User Plane Protocol User Plane (GTPv1-U)", 3GPP TS 29.281, V13.1.0,
(GTPv1-U)", 2016. March 2016.
Contributors
The authors would like to thank Andreas Schultz, Hong Liu, Yifan
Chen, Chunju Shao, Li Xue, Jianjie You, Jin Li, Joe Touch, Alexey
Melnikov, Kathleen Moriarty, Mirja Kuehlewind, Catherine Meadows, and
Paul Kyzivat for their valuable comments.
Authors' Addresses Authors' Addresses
Rong Zhang Rong Zhang
China Telecom China Telecom
No.109 Zhongshandadao avenue No.109 Zhongshandadao avenue
Guangzhou 510630 Guangzhou 510630
China China
Email: [email protected] Email: [email protected]
Rajesh S. Pazhyannur Rajesh S. Pazhyannur
Cisco Cisco
170 West Tasman Drive 170 West Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
USA United States of America
Email: [email protected] Email: [email protected]
Sri Gundavelli Sri Gundavelli
Cisco Cisco
170 West Tasman Drive 170 West Tasman Drive
San Jose, CA 95134 San Jose, CA 95134
USA United States of America
Email: [email protected] Email: [email protected]
Zhen Cao Zhen Cao
Huawei Huawei
Xinxi Rd. 3 Xinxi Rd. 3
Beijing 100085 Beijing 100085
China China
Email: [email protected] Email: [email protected]
Hui Deng Hui Deng
Huawei Huawei
Xinxi Rd. 3 Xinxi Rd. 3
Beijing 100085 Beijing 100085
China China
Email: [email protected] Email: [email protected]
Zongpeng Du Zongpeng Du
Huawei Huawei
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