draft-ietf-opsawg-capwap-alt-tunnel-04.txt   draft-ietf-opsawg-capwap-alt-tunnel-05.txt 
Network Working Group R. Zhang Network Working Group R. Zhang
Internet-Draft China Telecom Internet-Draft China Telecom
Intended status: Standards Track Z. Cao Intended status: Standards Track Z. Cao
Expires: May 14, 2015 H. Deng Expires: October 28, 2015 H. Deng
China Mobile China Mobile
R. Pazhyannur R. Pazhyannur
S. Gundavelli S. Gundavelli
Cisco Cisco
L. Xue L. Xue
Huawei Huawei
November 10, 2014 April 26, 2015
Alternate Tunnel Encapsulation for Data Frames in CAPWAP Alternate Tunnel Encapsulation for Data Frames in CAPWAP
draft-ietf-opsawg-capwap-alt-tunnel-04 draft-ietf-opsawg-capwap-alt-tunnel-05
Abstract Abstract
Control And Provisioning of Wireless Access Points (CAPWAP) defines a Control And Provisioning of Wireless Access Points (CAPWAP) defines a
specification to encapsulate a station's data frames between the specification to encapsulate 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
skipping to change at page 2, line 7 skipping to change at page 2, line 7
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
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Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on May 14, 2015. This Internet-Draft will expire on October 28, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Conventions used in this document . . . . . . . . . . . . 5 1.1. Conventions used in this document . . . . . . . . . . . . 6
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 6
2. Alternate Tunnel Encapsulation . . . . . . . . . . . . . . . 6 2. Alternate Tunnel Encapsulation . . . . . . . . . . . . . . . 7
2.1. Description . . . . . . . . . . . . . . . . . . . . . . . 6 2.1. Description . . . . . . . . . . . . . . . . . . . . . . . 7
3. Protocol Considerations . . . . . . . . . . . . . . . . . . . 8 3. Protocol Considerations . . . . . . . . . . . . . . . . . . . 9
3.1. Supported Alternate Tunnel Encapsulations . . . . . . . . 8 3.1. Supported Alternate Tunnel Encapsulations . . . . . . . . 9
3.2. Alternate Tunnel Encapsulations Type . . . . . . . . . . 9 3.2. Alternate Tunnel Encapsulations Type . . . . . . . . . . 10
3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication . . 10 3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication . . . 11
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 3.4. CAPWAP based Alternate Tunnel . . . . . . . . . . . . . . 11
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 3.5. PMIPv6 based Alternate Tunnel . . . . . . . . . . . . . . 12
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 12 3.6. Alternate Tunnel Information Elements . . . . . . . . . . 13
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 3.6.1. Access Router Information Sub-Elements . . . . . . . 13
7.1. Normative References . . . . . . . . . . . . . . . . . . 12 3.6.2. Tunnel DTLS Policy Sub-Element . . . . . . . . . . . 15
7.2. Informative References . . . . . . . . . . . . . . . . . 12 3.6.3. IEEE 802.11 Tagging Mode Policy Sub-Element . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 3.6.4. CAPWAP Transport Protocol Sub-Element . . . . . . . . 16
3.6.5. GRE Key Sub-Element . . . . . . . . . . . . . . . . . 17
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
5. Security Considerations . . . . . . . . . . . . . . . . . . . 19
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 19
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 19
7.1. Normative References . . . . . . . . . . . . . . . . . . 19
7.2. Informative References . . . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
1. Introduction 1. Introduction
Service Providers are deploying very large Wi-Fi deployments (ranging Service Providers are deploying very large Wi-Fi deployments (ranging
from hundreds of thousands of Access Points, APs (referred to as WTPs from hundreds of thousands of Access Points, APs (referred to as WTPs
in CAPWAP terminology) to millions of APs. These networks are in CAPWAP terminology) to millions of APs. These networks are
designed to carry traffic generated from mobile users. The volume in designed to carry traffic generated from mobile users. The volume in
mobile user traffic is already very large (in the order of petabytes mobile user traffic is already very large and expected to continue
per day) and expected to continue growing rapidly. As a result, growing rapidly. As a result, operators are looking for scalable
operators are looking for scalable solutions that can meet the solutions that can meet the increasing demand. The scalability
increasing demand. The scalability requirement can be met by requirement can be met by splitting the control/management plane from
splitting the control/management plane from the data plane. This the data plane. This enables the data plane to scale independent of
enables the data plane to scale independent of the control/management the control/management plane. This specification provides a way to
plane. This specification provides a way to enable such separation. enable such separation.
CAPWAP ([RFC5415], [RFC5416]) defines a tunnel mode that describes CAPWAP ([RFC5415], [RFC5416]) defines a tunnel mode that describes
how the WTP handles the data plane (user traffic). The following how the WTP handles the data plane (user traffic). The following
types are defined: types 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 AC in 802.3 o 802.3 Tunnel: All data frames are tunneled to the AC in 802.3
format. format.
o 802.11 Tunnel: All data frames are tunneled to the AC in 802.11 o 802.11 Tunnel: All data frames are tunneled to the AC in 802.11
format. format.
skipping to change at page 4, line 20 skipping to change at page 5, line 5
when they need to tunnel the user traffic. The tunneling requirement when they need to tunnel the user traffic. The tunneling requirement
may be driven by the need to apply policy at the Access Router or a may be driven by the need to apply policy at the Access Router or a
legal requirement to support lawful intercept of user traffic. This legal requirement to support lawful intercept of user traffic. This
requirement could be met in the locally bridged system (Figure 1) if requirement could be met in the locally bridged system (Figure 1) if
the access router implemented the required policy. However, in many the access router implemented the required policy. However, in many
deployments the operator managing the WTP is different than the deployments the operator managing the WTP is different than the
operator managing the Access Router. When the operators are operator managing the Access Router. When the operators are
different, the policy has to be enforced in a tunnel termination different, the policy has to be enforced in a tunnel termination
point in the WTP operator's network. point in the WTP operator's network.
+-----+ +-----+
| WTP | | WTP |
+-----+ +-----+
\\ \\
\\ CAPWAP Control Channel +----------+ \\
++=========================| AC | \\ CAPWAP Control Channel +----------+
// CAPWAP Data Channel: | | ++=========================| AC |
// IEEE 802.11 Mgmt traffic | | // CAPWAP Data Channel: | |
// Data Frames +----------+ // IEEE 802.11 Mgmt traffic | |
// // 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 system in Figure 2. 1) They do not There are two shortcomings with system in Figure 2. 1) They do not
allow the WTP to tunnel data frames to an endpoint different from the 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 any AC and 2) They do not allow the WTP to tunnel data frames using any
encapsulation other than CAPWAP (as specified in Section 4.4.2 of encapsulation other than CAPWAP (as specified in Section 4.4.2 of
[RFC5415]). [RFC5415]).
skipping to change at page 7, line 4 skipping to change at page 8, line 4
CAPWAP Data Channel: A bi-directional flow defined by the AC IP CAPWAP Data Channel: A bi-directional 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).
2. Alternate Tunnel Encapsulation 2. Alternate Tunnel Encapsulation
2.1. Description 2.1. Description
+-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+
| WTP | | AC | | WTP | | AC |
+-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+
|Join Request[Supported Alternate Tunnel | |Join Request[Supported Alternate Tunnel |
| Encapsulations ] | | Encapsulations ] |
|---------------------------------------->| |---------------------------------------->|
| | | |
|Join Response | |Join Response |
|<----------------------------------------| |<----------------------------------------|
| | | |
|IEEE 802.11 WLAN Config. Request [ | |IEEE 802.11 WLAN Config. Request [ |
| IEEE 802.11 Add WLAN, | | IEEE 802.11 Add WLAN, |
| Alternate Tunnel Encapsulation ( | | Alternate Tunnel Encapsulation ( |
| Tunnel Type, Tunnel Info Element) | | Tunnel Type, Tunnel Info Element) |
| ] | | ] |
|<----------------------------------------| |<----------------------------------------|
| | | |
| | | |
+-+-+-+-+-+-+ | +-+-+-+-+-+-+ |
| Setup | | | Setup | |
| Alternate | | | Alternate | |
| Tunnel | | | Tunnel | |
+-+-+-+-+-+-+ | +-+-+-+-+-+-+ |
| | | |
|IEEE 802.11 WLAN Config. Response | |IEEE 802.11 WLAN Config. Response |
|---------------------------------------->| |---------------------------------------->|
| | | |
| | | |
+-+-+-+-+-+-+ | +-+-+-+-+-+-+ |
| Tunnel | | | Tunnel | |
| Failure | | | Failure | |
+-+-+-+-+-+-+ | +-+-+-+-+-+-+ |
|WTP Alternate Tunnel Failure Indication | |WTP Alternate Tunnel Failure Indication |
|(report failure) | |(report failure) |
|---------------------------------------->| |---------------------------------------->|
| | | |
+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+ |
| Tunnel | | | Tunnel | |
| Established | | | Established | |
+-+-+-+-+-+-+-+ | +-+-+-+-+-+-+-+ |
|WTP Alternate Tunnel Failure Indication | |WTP Alternate Tunnel Failure Indication |
|(report clearing failure) | |(report clearing failure) |
|---------------------------------------->| |---------------------------------------->|
| | | |
Figure 4: Setup of Alternate Tunnel Figure 4: Setup of 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 encapsulation message element containing the
tunnel type and a tunnel-specific information element. (The tunnel- tunnel type and a tunnel-specific information element. (The tunnel-
skipping to change at page 8, line 42 skipping to change at page 9, line 42
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. Protocol Considerations 3. Protocol Considerations
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 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0 1 2 3 4 5 6 7 0
+=+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Num_Tunnels | Tunnel-Type 1 | Tunnel-Type [2..N] | Num_Tunnels | Tunnel-Type 1 | Tunnel-Type [2..N]
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Supported Alternate Tunnel Encapsulations Figure 5: Supported Alternate Tunnel Encapsulations
o Type: <IANA-1> for Supported Alternate Tunnel Encapsulations Type: <IANA-1> for Supported Alternate Tunnel Encapsulations
o Length: The length in bytes is 1 + Num_Tunnels Length: The length in bytes is 1 + Num_Tunnels
o Num_Tunnels: This refers to number of tunnel types present in the Num_Tunnels: This refers to number of tunnel types present in the
message element. At least one tunnel type must be present. message element. At least one tunnel type must be present.
o Tunnel-Type: This is identified by value defined in Section 3.2 Tunnel-Type: This is identified by value defined in Section 3.2
3.2. Alternate Tunnel Encapsulations Type 3.2. Alternate Tunnel Encapsulations Type
This message element is sent by the AC. This message element allows This message element is sent by the AC. This message element allows
the AC to select the alternate tunnel encapsulation. This message the AC to select the alternate tunnel encapsulation. This message
element may be provided along with the IEEE 802.11 Add WLAN message element may be provided along with the IEEE 802.11 Add WLAN message
element. When the message element is present the following fields of element. When the message element is present the following fields of
the IEEE 802.11 Add WLAN element shall be set as follows: MAC mode is the IEEE 802.11 Add WLAN element shall be set as follows: MAC mode is
set to 0 (Local MAC) and Tunnel Mode is set to 0 (Local Bridging). set to 0 (Local MAC) and Tunnel Mode is set to 0 (Local Bridging).
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 6: Alternate Tunnel Encapsulations Type Figure 6: Alternate Tunnel Encapsulations Type
o Type: <IANA-2> for Alternate Tunnel Encapsulation Type Type: <IANA-2> for Alternate Tunnel Encapsulation Type
o Length: > 4 Length: > 4
o Tunnel-Type: The tunnel type is specified by a 2 byte value. This Tunnel-Type: The tunnel type is specified by a 2 byte value. This
specification defines the values from zero (0) to five (5) as specification defines the values from zero (0) to five (5) as
given below. The remaining values are reserved for future use. given below. The remaining values are reserved for future use.
* 0: CAPWAP. This refers to a CAPWAP data channel described in 0: CAPWAP. This refers to a CAPWAP data channel described in
[RFC5415][RFC5416]. [RFC5415][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. This refers to the tunneling encapsulation 4: PMIPv6. This refers to the tunneling encapsulation
described in [RFC5213] described in [RFC5213]
* 5: GRE-IPv4. This refers to GRE encapsulation with IPv4 as the 5: GRE-IPv4. This refers to GRE encapsulation with IPv4 as the
delivery protocol as described in [RFC2784] delivery protocol as described in RFC2874.
* 6: GRE-IPv6. This refers to GRE encapsulation with IPv6 as the 6: GRE-IPv6. This refers to GRE encapsulation with IPv6 as the
delivery protocol as described in [RFC2784] delivery protocol as described in RFC2874.
Info Element: This field contains tunnel specific configuration
o Info Element: This field contains tunnel specific configuration parameters to enable the WTP to setup the alternate tunnel. This
parameters to enable the WTP to setup the alternate tunnel. For specification provides details for this elements for CAPWAP and
example if the tunnel type is CAPWAP then this field may contain PMIPv6. We anticipate that message elements for the other
the following (non-exhaustive) list of parameters protocols (like L2TPv3, etc) will be defined in other
specifications in the future
* Access Router IPv4 address
* Access Router IPv6 address
* Tunnel DTLS Policy
* IEEE 802.11 Tagging Policy
This specification only defines a generic container for such
message elements. We anticipate that these message elements (for
the different protocols) will be defined in separate documents,
potentially one for each tunneling protocols.
3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication 3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication
The Alternate Tunnel Encapsulation message element is sent by the WTP The Alternate Tunnel Failure Indication message element is sent by
to inform the AC about the status of the Alternate Tunnel. The the WTP to inform the AC about the status of the Alternate Tunnel.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Radio ID | WLAN ID | Status | Reserved | | Radio ID | WLAN ID | Status | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 7: IEEE 802.11 WTP Alternate Tunnel Failure Indication Figure 7: IEEE 802.11 WTP Alternate Tunnel Failure Indication
o Type: <IANA-3> for IEEE 802.11 WTP Alternate Tunnel Failure Type: <IANA-3> for IEEE 802.11 WTP Alternate Tunnel Failure
Indication Indication
o Length: == 4 Length: == 4
o Radio ID: The Radio Identifier, whose value is between one (1) and Radio ID: The Radio Identifier, whose value is between one (1) and
31, typically refers to some interface index on the WTP. 31, typically refers to some interface index on the WTP.
o WLAN ID: An 8-bit value specifying the WLAN Identifier. The value WLAN ID: An 8-bit value specifying the WLAN Identifier. The value
MUST be between one (1) and 16. MUST be between one (1) and 16.
o Status: An 8-bit boolean indicating whether the radio failure is 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 zero is used to clear the
event, while a value of one is used to report the event. event, while a value of one is used to report the event.
3.4. CAPWAP based Alternate Tunnel
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
should contain the following information:
o Access Router Information: IPv4 address or IPv6 address or Fully
Qualified Domain Name (FQDN), of the Access Router for the
alternate tunnel.
o Tunnel DTLS Policy: The CAPWAP protocol allows optional protection
of data packets using DTLS. Use of data packet protection on a
WTP is not mandatory but determined by the associated AC 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
CAPWAP data channel packet are to be tagged for QoS purposes (see
[RFC5416] for more details).
o CAPWAP Transport Protocol: The CAPWAP protocol supports both UDP
and UDP-Lite (see RFC3828). When run over IPv4, UDP is used for
the CAPWAP data channels. When run over IPv6, the CAPWAP data
channel may use either UDP or UDP-lite.
The message element structure for CAPWAP encapsulation is shown in
Figure 8:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type=0 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Sub-Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Tunnel DTLS Policy Sub-Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. IEEE 802.11 Tagging Mode Policy Sub-Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. CAPWAP Transport Protocol Sub-Element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Alternate Tunnel Encapsulation - CAPWAP
3.5. PMIPv6 based Alternate Tunnel
Proxy Mobile IPv6 (PMIPv6) (defined in [RFC5213]) can also be used
for alternate tunnel encapsulation between the WTP and the AR. In
this scenario, a WTP acts as the Mobile Access Gateway (MAG) function
that manages the mobility-related signaling for a station that is
attached to the WTP IEEE 802.11 radio access. The Local Mobility
Anchor (LMA) function is at the AR. If PMIPv6 encapsulation is
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
information:
o Access Router (acts as LMA) Information: IPv6 address or Fully
Qualified Domain Name (FQDN) for the alternate tunnel endpoint.
The message element structure for PMIPv6 encapsulation is shown in
Figure 9:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tunnel-Type=4 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router (LMA) Information Sub-element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Alternate Tunnel Encapsulation - PMIPv6
3.6. Alternate Tunnel Information Elements
This section defines the various sub-elements described in
Section 3.4 and Section 3.5
3.6.1. Access Router Information Sub-Elements
The Access Router Information Sub-Elements allow the AC to notify a
WTP of which AR(s) are available for establishing a data tunnel. The
AR information may be IPv4 address, IPv6 address, or AR domain name.
If a WTP obtains the correct AR FQDN, the Name-to-IP address mapping
is handled in the WTP (see RFC2782).
The following are the Access Router Information Sub-Elements defined
in this specification. The AC can use one of them to notify the
destination information of the data tunnel to the WTP. The Sub-
Elements containing the AR IPv4 address MUST NOT be used if an IPv6
data channel such as PMIPv6 or GREv6 is used.
3.6.1.1. AR IPv4 List Sub-Element
This Sub-Element (see Figure 10) is used by the AC to configure a WTP
with the AR IPv4 address available for the WTP to establish the data
tunnel for user traffic.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AR IPv4 Sub-Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-1 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-2 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv4 Address-N .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: AR IPv4 List Sub-Element
Length: This refers to the total length in octets of the sub-element
excluding the Type and Length fields.
AR IPv4 Address: IPv4 address of the AR. At least one IPv4 address
shall be present. Multiple addresses may be provided for load
balancing or redundancy.
3.6.1.2. AR IPv6 List Sub-Element
This Sub-Element (see Figure 11) is used by the AC to configure a WTP
with the AR IPv6 address available for the WTP to establish the data
tunnel for user traffic.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AR IPv6 Sub-Element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address-1 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address-2 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR IPv6 Address-N .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: AR IPv6 List Sub-Element
Length: This refers to the total length in octets of the sub-element
excluding the Type and Length fields.
AR IPv6 Address: IPv6 address of the AR. At least one IPv6 address
shall be present. Multiple addresses may be provided for load
balancing or redundancy.
3.6.1.3. AR FQDN List Sub-Element
This Sub-Element (see Figure 12) is used by the AC to configure a WTP
with AR FQDN available to establish the data tunnel for user traffic.
Based on the FQDN, a WTP can acquire the AR IP address via DNS.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AR FQDN Sub-Element Type | Sub-element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | AR FQDN-1 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | AR FQDN-2 .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length | AR FQDN-N .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: AR FQDN List Sub-Element
Sub-element Length: This refers to the total length in octets of the
sub-element excluding the Type and sub-element Length fields.
Length: The length of each AR FQDN.
AR FQDN: An array of variable-length string containing AR FQDN. This
can be used to satisfy load-balance and reliability requirements.
3.6.2. Tunnel DTLS Policy Sub-Element
The AC distributes its DTLS usage policy for the CAPWAP data tunnel
between a WTP and the AR. There are multiple supported options,
represented by the bit field below as defined in AC Descriptor
message elements. The WTP MUST abide by one of the options for
tunneling user traffic with AR. The Tunnel DTLS Policy Sub-Element
obey the definition in [RFC5415]. If there are more than one ARs
information provided by the AC for reliability reasons, the same
Tunnel DTLS Policy (see Figure 13) is generally applied for all
tunnels associated with the ARs. Otherwise, Tunnel DTLS Policy MUST
be bonding together with each of the ARs, then WTP will enforce the
independent tunnel DTLS policy for each tunnel with a specific AR.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Tunnel DTLS Sub-element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |A|D|C|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information (optional) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13: Tunnel DTLS Policy Sub-Element
Reserved: A set of reserved bits for future use. All implementations
complying with this protocol MUST set to zero any bits that are
reserved in the version of the protocol supported by that
implementation. Receivers MUST ignore all bits not defined for the
version of the protocol they support.
A: If A bit is set, there is an AR information associated with the
DTLS policy. There may be an array of pairs binding DTLS policy
information and AR information contained in the Tunnel DTLS Policy
Sub-Element. Otherwise, the same Tunnel DTLS Policy (see Figure 13)
is generally applied for all tunnels associated with the ARs
configured by the AC.
D: DTLS-Enabled Data Channel Supported (see [RFC5415]).
C: Clear Text Data Channel Supported (see [RFC5415]).
R: A reserved bit for future use abide (see [RFC5415]).
3.6.3. IEEE 802.11 Tagging Mode Policy Sub-Element
In 802.11 networks, IEEE 802.11 Tagging Mode Policy Sub-Element is
used to specify how the WTP apply the QoS tagging policy when
receiving the packets from stations on a particular radio. When the
WTP sends out the packet to data channel to the AR(s), the packets
have to be tagged for QoS purposes (see [RFC5416]).
The IEEE 802.11 Tagging Mode Policy abides the IEEE 802.11 WTP
Quality of Service defined in Section 6.22 of [RFC5416].
3.6.4. CAPWAP Transport Protocol Sub-Element
The CAPWAP data tunnel supports both UDP and UDP-Lite (see RFC3828).
When run over IPv4, UDP is used for the CAPWAP data channels. When
run over IPv6, the CAPWAP data channel may use either UDP or UDP-
lite. The AC specifies and configure the WTP for which transport
protocol is to be used for the CAPWAP data tunnel.
The CAPWAP Transport Protocol Sub-Element abides the definition in
Section 4.6.14 of [RFC5415].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=51 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Transport |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
CAPWAP Transport Protocol Sub-Element
Type: 51 for CAPWAP Transport Protocol [RFC5415].
Length: 1
Transport: The transport to use for the CAPWAP Data channel. The
following enumerated values are supported:
1 - UDP-Lite: The UDP-Lite transport protocol is to be used for the
CAPWAP Data channel. Note that this option MUST NOT be used if the
CAPWAP Control channel is being used over IPv4 and AR address is IPv4
contained in the AR Information Sub-Element.
2 - UDP: The UDP transport protocol is to be used for the CAPWAP Data
channel.
3.6.5. GRE Key Sub-Element
If a WTP receives the GRE Key Sub-Element in the Alternate Tunnel
Encapsulation message element for GREv4 or GREv6 selection, the WTP
must insert the GRE Key to the encapsulation packet (see [RFC2890]).
An AR acting as decapsulating tunnel endpoint identifies packets
belonging to a traffic flow based on the Key value.
The GRE Key Sub-Element field contains a four octet number defined in
[RFC2890].
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key Sub-element Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
GRE Key Sub-Element
GRE Key: The Key field contains a four octet number which is inserted
by the WTP according to [RFC2890].
4. IANA Considerations 4. IANA Considerations
This document requires the following IANA considerations. This document requires the following IANA considerations.
o <IANA-1>. This specification defines the Supported Alternate o <IANA-1>. This specification defines the Supported Alternate
Tunnel Encapsulations Type message element in Section 3.1. This Tunnel Encapsulations Type message element in Section 3.1. This
elements needs to be registered in the existing CAPWAP Message elements needs to be registered in the existing CAPWAP Message
Element Type registry, defined in [RFC5415]. The Type value for Element Type registry, defined in [RFC5415]. The Type value for
this element needs to be between 1 and 1023 (see Section 15.7 in this element needs to be between 1 and 1023 (see Section 15.7 in
[RFC5415]). [RFC5415]).
skipping to change at page 12, line 25 skipping to change at page 19, line 46
October 1996. October 1996.
[RFC2661] Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn, [RFC2661] Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn,
G., and B. Palter, "Layer Two Tunneling Protocol "L2TP"", G., and B. Palter, "Layer Two Tunneling Protocol "L2TP"",
RFC 2661, August 1999. RFC 2661, August 1999.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P. [RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784, Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
March 2000. March 2000.
[RFC2890] Dommety, G., "Key and Sequence Number Extensions to GRE",
RFC 2890, September 2000.
[RFC3828] Larzon, L-A., Degermark, M., Pink, S., Jonsson, L-E., and
G. Fairhurst, "The Lightweight User Datagram Protocol
(UDP-Lite)", RFC 3828, July 2004.
[RFC3931] Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling [RFC3931] Lau, J., Townsley, M., and I. Goyret, "Layer Two Tunneling
Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005. Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K., [RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008. and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[RFC5415] Calhoun, P., Montemurro, M., and D. Stanley, "Control And [RFC5415] Calhoun, P., Montemurro, M., and D. Stanley, "Control And
Provisioning of Wireless Access Points (CAPWAP) Protocol Provisioning of Wireless Access Points (CAPWAP) Protocol
Specification", RFC 5415, March 2009. Specification", RFC 5415, March 2009.
 End of changes. 28 change blocks. 
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