Internet DRAFT - draft-xue-opsawg-capwap-alt-tunnel-information
draft-xue-opsawg-capwap-alt-tunnel-information
Network Working Group D. Liu
Internet-Draft China Mobile
Intended status: Standards Track R. Zhang
Expires: April 27, 2015 China Telecom
L. Xue
J. Kaippallimalil
Huawei
R. Pazhyannur
S. Gundavelli
Cisco
October 24, 2014
Specification Alternate Tunnel Information for Data Frames in WLAN
draft-xue-opsawg-capwap-alt-tunnel-information-01
Abstract
In IEEE 802.11 Wireless Local Area Network (WLAN) architecture, in
order to satisfy the scalability requirement, customer data frames
are desired to be distributed to an endpoint as Access Router(AR)
different from the Access Controller (AC). For tunneling the data
frames, there are many known alternate tunnel technologies can be
used, such as IP-GRE, IP-in-IP, CAPWAP, L2TP/L2TPv3, etc. To assist
a WTP to set up the alternate tunnels for data plane, this document
extends the CAPWAP message elements.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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 http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
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This Internet-Draft will expire on April 27, 2015.
Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Data Frame Alternate Tunnel in WLAN . . . . . . . . . . . . . 4
2.1. CAPWAP . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. L2TP . . . . . . . . . . . . . . . . . . . . . . . . . . 5
2.3. L2TPv3 . . . . . . . . . . . . . . . . . . . . . . . . . 6
2.4. IP-in-IP . . . . . . . . . . . . . . . . . . . . . . . . 6
2.5. PMIPv6 . . . . . . . . . . . . . . . . . . . . . . . . . 7
2.6. GREv4/6 . . . . . . . . . . . . . . . . . . . . . . . . . 8
3. Alternate Tunnel Information Elements . . . . . . . . . . . . 9
3.1. Access Router Information Sub-Elements . . . . . . . . . 9
3.1.1. AR IPv4 Address Sub-Element . . . . . . . . . . . . . 9
3.1.2. AR IPv4 Address for Load-balance Sub-Element . . . . 10
3.1.3. AR IPv6 Address Sub-Element . . . . . . . . . . . . . 10
3.1.4. AR IPv6 Address for Load-balance Sub-Element . . . . 11
3.1.5. AR FQDN Sub-Element . . . . . . . . . . . . . . . . . 12
3.1.6. AR FQDN for Load-balance Sub-Element . . . . . . . . 12
3.2. Tunnel DTLS Policy Sub-Element . . . . . . . . . . . . . 13
3.3. IEEE 802.11 Tagging Mode Policy Sub-Element . . . . . . . 14
3.4. CAPWAP Transport Protocol Sub-Element . . . . . . . . . . 14
3.5. GRE Key Sub-Element . . . . . . . . . . . . . . . . . . . 15
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
5. Security Considerations . . . . . . . . . . . . . . . . . . . 15
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 15
6.1. Normative References . . . . . . . . . . . . . . . . . . 15
6.2. Informative References . . . . . . . . . . . . . . . . . 16
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 17
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1. Introduction
Control and Provisioning of Wireless Access Points (CAPWAP)
([RFC5415], [RFC5416]) defines CAPWAP tunnel mode which can be used
to encapsulate data frames and control/management frames of a station
between the Wireless Transmission Point (WTP) and the Access
Controller (AC). The customer data traffic on WTP can be either
locally bridged or tunneled to the AC. In practice, operators who
have deployed large numbers of WTPs desire to distribute the data
traffic to a different entity (e.g., Access Router) rather than the
AC for redundancy reasons. The architecture for tunneling WLAN user
data frames to ARs is defined in [I-D.ietf-opsawg-capwap-alt-tunnel]
and shown in Figure 1.
Tunnel to AR _________
+-----+ ( ) +-----------------+
| WTP |======+Internet +==============|Access Router(AR)|
+-----+ (_________} +-----------------+
\\ ________
\\ ( ) CAPWAP +--------+
++==Internet+===============| AC |
// ( ) +--------+
// ________
+-----+// ( ) +----------------+
| WTP |====+Internet +================| Access Router |
+=====+ (_________} +----------------+
Tunnel to AR
Figure 1: Centralized Control with Distributed Data
How the WTP can be configured with this alternate tunnel is already
defined in [I-D.ietf-opsawg-capwap-alt-tunnel]. However,
[I-D.ietf-opsawg-capwap-alt-tunnel] specifies only the generic
container of the extension CAPWAP message elements used for this
alternate tunnel (see Figure 2). The message elements information
rely on a binding specification for a particular alternate tunnel
protocol, such as GRE, IP-in-IP, CAPWAP, L2TP/L2TPv3 etc. This
specification defines the binding specific CAPWAP message elements
for using the different alternate tunnel protocols, one for each
alternate tunnel protocol. Different Alternate Tunnel sub-message
elements are defined.
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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 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Info Element
+-+-+-+-+-+-+-+-+-+-+
Figure 2: Alternate Tunnel Encapsulations Type
2. Data Frame Alternate Tunnel in WLAN
2.1. CAPWAP
When the WTP joins the AC, it should indicate its alternate tunnel
encapsulation capability and the CAPWAP protocol should be one
option. If the CAPWAP encapsulation is selected by the AC and
configured by the AC to the WTP, the Info Element field of the
generic encapsulation shown in Figure 2 should contain the following
information:
o Access Router Information: IPv4 address or IPv6 address or Fully
Qualified Domain Name (FQDN), which includes the Access Router
information with which the WTP can associated for tunneling the
user traffic.
o Tunnel DTLS Policy: The CAPWAP protocol allows optional protection
of data packets using DTLS. Use of data packet protection on a
WTP is determined by the associated AC policy. When the AC
determines the DTLS is utilized, the D bit should be set.
Otherwise, clear data packets will be encapsulated (see
[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]).
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 3:
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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 3: Alternate Tunnel Encapsulation - CAPWAP
2.2. L2TP
Layer Two Tunneling Protocol (L2TP) can pass PPP frames over an L2TP
tunnel within a UDP datagram. When a AC selects the L2TP as the
alternate tunnel encapsulation and reports the selection to the WTP,
the WTP initiates the L2TP data tunnel establishment with the
specific AR(s). The AR whose responsibility is to be a L2TP Network
Server (LNS) (see [RFC2661]) should configure WTP during the calling
request from hosts attaching to the WTP in IEEE 802.11 network. For
L2TP, the Info Element field of the generic encapsulation shown in
Figure 2 should contain the following information (not-exhaustive):
o Access Router (acts as LNS) Information: IPv4 address or IPv6
address or Fully Qualified Domain Name (FQDN), which includes the
Access Router information with which the WTP can associate for
tunneling the user traffic.
The message element structure for L2TP encapsulation is shown in
Figure 4:
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=1 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router (LNS) Information Sub-element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Alternate Tunnel Encapsulation - L2TP
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2.3. L2TPv3
L2TPv3 (see [RFC3931]) borrows largely from L2TPv2. L2TPv3 tunnel
can be used over multiple Packet-Switched Networks (PSN) such as IP,
UDP, Frame Relay, ATM, MPLS, etc. L2TPv3 data tunnels may be
utilized with or without the L2TP control channel, either via manual
configuration or via other signaling methods to per-configure or
distribute L2TP session information. In this document, L2TPv3
control channel is assumed to establish, manage and tear down the
L2TPv3 data tunnels. For L2TPv3, the Info Element field of the
generic encapsulation shown in Figure 2 should contain the following
information:
o Access Router (acts as LNS) Information: IPv4 address or IPv6
address or Fully Qualified Domain Name (FQDN), which includes the
Access Router information with which the WTP can associate for
tunneling the user traffic.
The message element structure for L2TPv3 encapsulation is shown in
Figure 5:
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=2 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router (LNS) Information Sub-element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Alternate Tunnel Encapsulation - L2TPv3
2.4. IP-in-IP
If IP-in-IP encapsulation (see [RFC2003]) is selected by AC, the user
traffic that arrives to a WTP is encapsulated within IP datagrams and
delivered to an intermediate destination which is the Access Router.
Once the encapsulated datagram arrives the AR, it is decapsulated.
In the general case, the encapsulator WTP should obtain the AR as the
decapsulator. If IP-in-IP encapsulation is selected by AC and
configured by AC to WTP, the Info Element field of the generic
encapsulation shown in Figure 2 should contain the following
information:
o Access Router Information: IPv4 address or IPv6 address or Fully
Qualified Domain Name (FQDN), which includes the Access Router
information with which the WTP can associate for tunneling the
user traffic.
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The message element structure for IP-in-IP encapsulation is shown in
Figure 6:
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=3 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Sub-element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: Alternate Tunnel Encapsulation - IP-in-IP
2.5. PMIPv6
Proxy Mobile IPv6 (PMIPv6, see [RFC5213]) is one option for alternate
tunnel encapsulation between the WTP and the AR. In this scenario, a
WTP should act 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 should be located at the AR. In Proxy Mobile IPv6, the
address of the LMA should be discovered by the MAG. If PMIPv6
encapsulation is selected by the AC and configured by the AC to a
WTP, the Info Element field of the generic encapsulation shown in
Figure 2 should contain the following information:
o Access Router (acts as LMA) Information: IPv6 address or Fully
Qualified Domain Name (FQDN), which includes the Access Router
information with which the WTP can associate for tunneling the
user traffic.
The message element structure for PMIPv6 encapsulation is shown in
Figure 7:
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 7: Alternate Tunnel Encapsulation - PMIPv6
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2.6. GREv4/6
In order to encapsulate data traffic using GREv4/6 (see and
[RFC1701][RFC2784]), the WTP needs to obtain the destination node IP
address of a GRE tunnel (e.g., the AR address). Optionally, GRE Key
Sub-element (see [RFC2784] and [RFC2890]) is needed for WTP to
configure the complementary tunnel information. If WTP obtains the
GRE Key Sub-element, the key MUST be inserted into the GRE
encapsulation header. The Key is used for identifying extra context
information about the received payload on AR. If the WTP obtains the
Key information from the AC, the payload packets without the
correspondent GRE Key or with an unmatched GRE Key will be silently
dropped on the AR. For GRE, the Info Element field of the generic
encapsulation shown in Figure 2 should contain the following
information (not-exhaustive):
o Access Router Information: IPv4 address (for GREv4) or IPv6
address (for GREv6) or Fully Qualified Domain Name (FQDN) (For
both GREv4 and GREv6), which includes the Access Router
information with which the WTP can associate for tunneling the
user traffic.
o GRE Key: The Key field contains a four octet number which is
inserted by the WTP as defined in [RFC2890].
The message element structure for GREv4 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=5 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Sub-element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. GRE Key Sub-element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 8: Alternate Tunnel Encapsulation - GREv4
The message element structure for GREv6 encapsulation is shown in
Figure 9:
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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=6 | Info Element Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. Access Router Information Sub-element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. GRE Key Sub-element .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: Alternate Tunnel Encapsulation - GREv6
3. Alternate Tunnel Information Elements
3.1. 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.
3.1.1. AR IPv4 Address 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=1 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+
. AR IPv4 Address .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: AR IPv4 Address Sub-Element
Type: 1 for AR IPv4 Address
Length: 4
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AR IPv4 Address: 32-bit integer containing AR IPv4 Address.
3.1.2. AR IPv4 Address for Load-balance Sub-Element
This Sub-Element (see Figure 11) is used to satisfy load-balance and
reliability requirements. There may be multiple AR addresses
available for a WTP and provided by an AC. The WTP can use the AR
information to send 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=2 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+
| Priority | AR IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .
+-+-+-+-+
Figure 11: AR IPv4 Address for Load-balance Sub-Element
Type: 2 for AR IPv4 Address for Load-balance
Length:>=5
Priority: A value between 1 and 255 specifying the priority order for
the preferred AR. For instance, the value of one (1) is used to set
the primary AR, the value of two (2) is used to set the secondary;
two instances with the same value are used for load-balance, etc.
AR IPv4 Address: 32-bit integer containing AR IPv4 Address binding
with the specific priority. There may be an array of pairs binding
priority and AR IPv4 address.
3.1.3. AR IPv6 Address Sub-Element
This Sub-Element (see Figure 12) 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.
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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=3 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+
. AR IPv6 Address .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: AR IPv6 Address Sub-Element
Type: 3 for AR IPv6 Address
Length: 16
AR IPv6 Address: 128-bit integer containing AR IPv6 Address
3.1.4. AR IPv6 Address for Load-balance Sub-Element
This Sub-Element (see Figure 13) is used to satisfy load-balance and
reliability requirements. There may be multiple AR addresses
available for a WTP and provided by an AC. A WTP can use the AR
information to send 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=4 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+
| Priority | AR IPv6 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .
+-+-+-+-+
Figure 13: AR IPv6 Address for Load-balance Sub-Element
Type: 4 for AR IPv6 Address for Load-balance
Length:>= 17
Priority: A value between 1 and 255 specifying the priority order of
the preferred AR. For instance, the value of one (1) is used to set
the primary AR, the value of two (2) is used to set the secondary;
two instances with the same value are used for load-balance, etc.
AR IPv6 Address: 128-bit integer containing AR IPv6 Address binding
with the specific priority. There may be an array of pairs binding
priority and AR IPv6 address.
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3.1.5. AR FQDN Sub-Element
This Sub-Element (see Figure 14) 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=5 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+
. AR FQDN .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: AR FQDN Sub-Element
Type: 5 for AR FQDN
Length:>=1
AR FQDN: A variable-length string containing the AR FQDN.
3.1.6. AR FQDN for Load-balance Sub-Element
This Sub-Element (see Figure 15) is used to satisfy load-balance and
reliability requirements. There may be multiple AR FQDNs available
for a WTP and provided by an AC. A WTP can use the AR information to
send 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=6 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-------------------------------+
| Priority | AR FQDN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| .
+-+-+-+-+
Figure 15: AR FQDN for Load-balance Sub-Element
Type: 6 for AR FQDN for Load-balance
Prefer: A value between 1 and 255 specifying the priority order of
the preferred AR. For instance, the value of one (1) is used to set
the primary AR, the value of two (2) is used to set the secondary;
two instances with the same value are used for load-balance, etc.
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AR FQDN: Variable-length string containing AR FQDN binding with the
specific priority. There may be an array of pairs binding priority
and AR FQDN.
3.2. 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 16) 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=7 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved |A|D|C|R|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. AR Information (optional) .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 16: Tunnel DTLS Policy Sub-Element
Type: 7 for Tunnel DTLS Policy
Length: >=6
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 16)
is generally applied for all tunnels associated with the ARs
configured by the AC.
D: DTLS-Enabled Data Channel Supported (see [RFC5415]).
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C: Clear Text Data Channel Supported (see [RFC5415]).
R: A reserved bit for future use abide (see [RFC5415]).
3.3. 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].
3.4. 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.
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2 - UDP: The UDP transport protocol is to be used for the CAPWAP Data
channel.
3.5. 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=8 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| GRE Key |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
GRE Key Sub-Element
Type: 8 for GRE Key Sub-Element
Length: 4
GRE Key: The Key field contains a four octet number which is inserted
by the WTP according to [RFC2890].
4. IANA Considerations
To be specified in later versions.
5. Security Considerations
To be specified in later versions.
6. References
6.1. Normative References
[RFC1701] Hanks, S., Li, T., Farinacci, D., and P. Traina, "Generic
Routing Encapsulation (GRE)", RFC 1701, October 1994.
[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003,
October 1996.
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[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
[RFC2661] Townsley, W., Valencia, A., Rubens, A., Pall, G., Zorn,
G., and B. Palter, "Layer Two Tunneling Protocol "L2TP"",
RFC 2661, August 1999.
[RFC2782] Gulbrandsen, A., Vixie, P., and L. Esibov, "A DNS RR for
specifying the location of services (DNS SRV)", RFC 2782,
February 2000.
[RFC2784] Farinacci, D., Li, T., Hanks, S., Meyer, D., and P.
Traina, "Generic Routing Encapsulation (GRE)", RFC 2784,
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
Protocol - Version 3 (L2TPv3)", RFC 3931, March 2005.
[RFC4347] Rescorla, E. and N. Modadugu, "Datagram Transport Layer
Security", RFC 4347, April 2006.
[RFC5213] Gundavelli, S., Leung, K., Devarapalli, V., Chowdhury, K.,
and B. Patil, "Proxy Mobile IPv6", RFC 5213, August 2008.
[RFC5415] Calhoun, P., Montemurro, M., and D. Stanley, "Control And
Provisioning of Wireless Access Points (CAPWAP) Protocol
Specification", RFC 5415, March 2009.
[RFC5416] Calhoun, P., Montemurro, M., and D. Stanley, "Control and
Provisioning of Wireless Access Points (CAPWAP) Protocol
Binding for IEEE 802.11", RFC 5416, March 2009.
6.2. Informative References
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[I-D.ietf-opsawg-capwap-alt-tunnel]
Zhang, R., Cao, Z., Deng, H., Pazhyannur, R., Gundavelli,
S., and L. Xue, "Alternate Tunnel Encapsulation for Data
Frames in CAPWAP", draft-ietf-opsawg-capwap-alt-tunnel-03
(work in progress), September 2014.
Authors' Addresses
Dapeng Liu
China Mobile
Unit 2, 28 Xuanwumenxi Ave, Xuanwu District
Beijing 100053
China
Email: liudapeng@chinamobile.com
Rong Zhang
China Telecom
No. 109 Zhongshandadao avenue
Guangzhou 510630
China
Email: zhangr@gsta.com
Li Xue
Huawei
No. 156 Beiqing Rd. Z-park, Shi-Chuang-Ke-Ji-Shi-Fan-Yuan
Beijing, Haidian District 100095
China
Email: xueli@huawei.com
John Kaippallimalil
Huawei
5430 Legacy Drive, Suite 175
Plano, TX 75024
Email: john.kaippallimalil@huawei.com
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Rajesh S. Pazhyannur
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: rpazhyan@cisco.com
Sri Gundavelli
Cisco
170 West Tasman Drive
San Jose, CA 95134
USA
Email: sgundave@cisco.com
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