draft-ietf-opsawg-capwap-alt-tunnel-02.txt   draft-ietf-opsawg-capwap-alt-tunnel-03.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: March 1, 2015 H. Deng Expires: March 12, 2015 H. Deng
China Mobile China Mobile
R. Pazhyannur R. Pazhyannur
S. Gundavelli S. Gundavelli
Cisco Cisco
L. Xue L. Xue
Huawei Huawei
August 28, 2014 September 8, 2014
Alternate Tunnel Encapsulation for Data Frames in CAPWAP Alternate Tunnel Encapsulation for Data Frames in CAPWAP
draft-ietf-opsawg-capwap-alt-tunnel-02 draft-ietf-opsawg-capwap-alt-tunnel-03
Abstract Abstract
CAPWAP defines a specification to encapsulate a station's data frames Control And Provisioning of Wireless Access Points (CAPWAP) defines a
between the Wireless Transmission Point (WTP) and Access Controller specification to encapsulate a station's data frames between the
(AC) using CAPWAP. Specifically, the station's IEEE 802.11 data Wireless Transmission Point (WTP) and Access Controller (AC).
frames can be either locally bridged or tunneled to the AC. When Specifically, the station's IEEE 802.11 data frames can be either
tunneled, a CAPWAP data channel is used for tunneling. In many locally bridged or tunneled to the AC. When tunneled, a CAPWAP data
deployments it is desirable to encapsulate date frames to an entity channel is used for tunneling. In many deployments encapsulating
different from the AC for example to an Access Router (AR). Further, data frames to an entity other than the AC (for example to an Access
it may also be desirable to use different tunnel encapsulations to Router (AR)) is desirable. Further, it may also be desirable to use
carry the stations' data frames. This document provides a different tunnel encapsulations to carry the stations' data frames.
specification for this and refers to it as Alternate tunnel This document provides a specification for this and refers to it as
encapsulation. The Alternate tunnel encapsulation allows 1) the WTP Alternate tunnel encapsulation. The Alternate tunnel encapsulation
to tunnel non-management data frames to an endpoint different from allows 1) the WTP to tunnel non-management data frames to an endpoint
the AC and 2) the WTP to tunnel using one of many known encapsulation different from the AC and 2) the WTP to tunnel using one of many
types such as IP-IP, IP-GRE, CAPWAP. The WTP may advertise support known encapsulation types such as IP-IP, IP-GRE, CAPWAP. The WTP may
for Alternate tunnel encapsulation during the discovery or join advertise support for Alternate tunnel encapsulation during the
process and AC may select one of the supported Alternate Tunnel discovery or join process and AC may select one of the supported
encapsulation types while configuring the WTP. 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 Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
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
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
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 March 1, 2015. This Internet-Draft will expire on March 12, 2015.
Copyright Notice Copyright Notice
Copyright (c) 2014 IETF Trust and the persons identified as the Copyright (c) 2014 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
This document is subject to BCP 78 and the IETF Trust's Legal This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of (http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents publication of this document. Please review these documents
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1.1. Conventions used in this document . . . . . . . . . . . . 5 1.1. Conventions used in this document . . . . . . . . . . . . 5
1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5 1.2. Terminology . . . . . . . . . . . . . . . . . . . . . . . 5
2. Alternate Tunnel Encapsulation . . . . . . . . . . . . . . . 6 2. Alternate Tunnel Encapsulation . . . . . . . . . . . . . . . 6
2.1. Description . . . . . . . . . . . . . . . . . . . . . . . 6 2.1. Description . . . . . . . . . . . . . . . . . . . . . . . 6
3. Protocol Considerations . . . . . . . . . . . . . . . . . . . 8 3. Protocol Considerations . . . . . . . . . . . . . . . . . . . 8
3.1. Supported Alternate Tunnel Encapsulations . . . . . . . . 8 3.1. Supported Alternate Tunnel Encapsulations . . . . . . . . 8
3.2. Alternate Tunnel Encapsulations Type . . . . . . . . . . 9 3.2. Alternate Tunnel Encapsulations Type . . . . . . . . . . 9
3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication . . 10 3.3. IEEE 802.11 WTP Alternate Tunnel Failure Indication . . 10
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 11 6. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 12
7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 12
7.1. Normative References . . . . . . . . . . . . . . . . . . 12 7.1. Normative References . . . . . . . . . . . . . . . . . . 12
7.2. Informative References . . . . . . . . . . . . . . . . . 12 7.2. Informative References . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 13
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 APs (referred to as WTPs in CAPWAP from hundreds of thousands of APs (referred to as WTPs in CAPWAP
terminology) to millions of APs). These networks are designed to terminology) to millions of APs). These networks are designed to
carry traffic generated from mobile users. The volume in mobile user carry traffic generated from mobile users. The volume in mobile user
traffic is already very large (in the order of petabytes per day) and traffic is already very large (in the order of petabytes per day) and
expected to continue growing rapidly. As a result, operators are expected to continue growing rapidly. As a result, operators are
looking for solutions that can scale to meet the increasing demand. looking for solutions that can scale to meet the increasing demand.
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stations associated with the WLAN. The following types are stations associated with the WLAN. The following types are
supported: supported:
o Local Bridging: All user traffic is to be locally bridged. o Local Bridging: All user traffic is to be locally bridged.
o 802.3 Tunnel: All user traffic is to be tunneled to the AC in o 802.3 Tunnel: All user traffic is to be tunneled to the AC in
802.3 format. 802.3 format.
o 802.11 Tunnel: All user traffic is to be tunneled to the AC in o 802.11 Tunnel: All user traffic is to be tunneled to the AC in
802.11 format. 802.11 format.
There are two shortcomings with currently specified tunneled modes: There are two shortcomings with currently specified tunneled modes:
1) it does not allow the WTP to tunnel data frames to an endpoint 1) They do not allow the WTP to tunnel data frames to an endpoint
different from the AC and 2) it does not allow the WTP to tunnel data different from the AC and 2) They do not allow the WTP to tunnel data
frames using any encapsulation other than CAPWAP (as specified in frames using any encapsulation other than CAPWAP (as specified in
Section 4.4.2 of [RFC5415]). Next, we describe what is driving the Section 4.4.2 of [RFC5415]). Next, we describe what is driving the
above mentioned two requirements. above mentioned two requirements.
Some operators deploying large number of Access Points prefer to Some operators deploying large number of Access Points prefer to
centralize the management and control of Access Points while centralize the management and control of Access Points while
distributing the handling of data traffic to increase scaling. This distributing the handling of data traffic to increase scaling. This
motivates an architecture as shown in Figure 1 that has the AC in a motivates an architecture as shown in Figure 1 that has the AC in a
centralized location and one or more tunnel gateways (or Access centralized location and one or more tunnel gateways (or Access
Routers) that terminate the data tunnels from the various WTPs. This Routers) that terminate the data tunnels from the various WTPs. This
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The above system (shown in Figure 1) could be achieved by setting the The above system (shown in Figure 1) could be achieved by setting the
tunnel mode to Local bridging. In such a case the AC would handle tunnel mode to Local bridging. In such a case the AC would handle
control of WTPs as well as handle the management traffic to/from the control of WTPs as well as handle the management traffic to/from the
stations. There is CAPWAP Control and Data Channel between the WTP stations. There is CAPWAP Control and Data Channel between the WTP
and the AC. The CAPWAP Data channel carries the IEEE 802.11 and the AC. The CAPWAP Data channel carries the IEEE 802.11
management traffic (like IEEE 802.11 Action Frames). The station's management traffic (like IEEE 802.11 Action Frames). The station's
data frames are locally bridged, i.e., not carried over the CAPWAP data frames are locally bridged, i.e., not carried over the CAPWAP
data channel. The station's data frames are handled by the Access data channel. The station's data frames are handled by the Access
Router. However, in many deployments the operator managing the WTPs/ Router. However, in many deployments the operator managing the WTPs/
AC may be different from the operator providing the internet AC may be different from the operator providing the Internet
connectivity to the WTPs. Further, the WTP operator may want (or be connectivity to the WTPs. Further, the WTP operator may want (or be
required by legal/regulatory requirements) to tunnel the traffic back required by legal/regulatory requirements) to tunnel the traffic back
to an Access Router in its network as shown in Figure 2. The to an Access Router in its network as shown in Figure 2. The
tunneling requirement may be driven by the need to apply policy at tunneling requirement may be driven by the need to apply policy at
the Access Router or a legal requirement to support lawful intercept the Access Router or a legal requirement to support lawful intercept
of user traffic. What this means is that local bridging does not of user traffic. What this means is that local bridging does not
meet their requirements. Their requirements are met either by having meet their requirements. Their requirements are met either by having
the WTP tunnel the station's traffic to the AC or the WTP support an the WTP tunnel the station's traffic to the AC or the WTP support an
alternate tunnel, i.e., a tunnel to an alternate entity different alternate tunnel, i.e., a tunnel to an alternate entity different
from the AC. This is the motivation for Alternate Tunnel from the AC. This is the motivation for Alternate Tunnel
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Figure 2: Centralized Control with Distributed Data Figure 2: Centralized Control with Distributed Data
In the case where the WTP is tunneling data frames to an AR (and not In the case where the WTP is tunneling data frames to an AR (and not
the AC), the choice of tunnel encapsulation need not be restricted the AC), the choice of tunnel encapsulation need not be restricted
only to CAPWAP (as described in Section 4.4.2 of [RFC5415]). In only to CAPWAP (as described in Section 4.4.2 of [RFC5415]). In
fact, the WTP may additionally support other widely used fact, the WTP may additionally support other widely used
encapsulation types such as L2TP, L2TPv3, IP-in-IP, IP/GRE, etc. The encapsulation types such as L2TP, L2TPv3, IP-in-IP, IP/GRE, etc. The
WTP may advertise the different alternate tunnel encapsulation types WTP may advertise the different alternate tunnel encapsulation types
supported and the AC can select one of the supported encapsulation supported and the AC can select one of the supported encapsulation
types. As shown in the figure there is still a CAPWAP control and types. As shown in the figure there is still a CAPWAP control and
data channel between the WTP and AC wherein the CAPWAP data channel data channel between the WTP and AC, wherein the CAPWAP data channel
carries the stations' management traffic. Thus the WTP will maintain carries the stations' management traffic. Thus the WTP will maintain
three tunnels: CAPWAP Control, CAPWAP Data, and another (alternate) three tunnels: CAPWAP Control, CAPWAP Data, and another (alternate)
tunnel to the AR. The main reason to maintain a CAPWAP data channel tunnel to the AR. The main reason to maintain a CAPWAP data channel
is to minimize the changes on the WTP and AC required to transport is to minimize the changes on the WTP and AC required to transport
stations' management frames (like EAP, IEEE 802.11 Action Frames). stations' management frames (like EAP, IEEE 802.11 Action Frames).
These management frames are transported over the CAPWAP data channel These management frames are transported over the CAPWAP data channel,
as they are done for case when the WTP's tunnel mode is configured as as they are when the WTP's tunnel mode is configured as local
the local bridging. In this specification we describe how the WTP bridging. In this specification we describe how the WTP can be
can be configured with this alternate tunnel. configured with this alternate tunnel.
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", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119] document are to be interpreted as described in [RFC2119]
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
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needs to be between 1 and 1023. needs to be between 1 and 1023.
o <IANA-3>. This specification defines the IEEE 802.11 WTP o <IANA-3>. This specification defines the IEEE 802.11 WTP
Alternate Tunnel Failure Indication message element in Alternate Tunnel Failure Indication message element in
Section 3.3. This element needs to be registered in the existing Section 3.3. This element needs to be registered in the existing
CAPWAP Message Element Type registry, defined in [RFC5415]. The CAPWAP Message Element Type registry, defined in [RFC5415]. The
Type value for this element needs to be between 1024 and 2047. Type value for this element needs to be between 1024 and 2047.
o Tunnel-Type: This specification defines the Alternate Tunnel o Tunnel-Type: This specification defines the Alternate Tunnel
Encapsulations Type message element. This element contains a Encapsulations Type message element. This element contains a
field Tunnel-Type. The namespace for the field is 16 bits field Tunnel-Type. The namespace for the field is 16 bits
(0-65535)). This specification defines values, zero (0) through (0-65535)). This specification defines values, zero (0) through
six (6) and can be found in Section 3.2. The remaining values six (6) and can be found in Section 3.2. Future allocations of
(6-65535) are controlled and maintained by IANA and require an values in this name space are to be assigned by IANA using the
Expert Review. IANA needs to create a Tunnel-Type registry whose "Specification Required" policy. IANA needs to create a registry
format is given below. called CAPWAP Alternate Tunnel-Types. The registry format is
given below.
Tunnel-Type Type Value Reference Tunnel-Type Type Value Reference
CAPWAP 0 CAPWAP 0
L2TP 1 L2TP 1
L2TPv3 2 L2TPv3 2
IP-IP 3 IP-IP 3
PMIPv6 4 PMIPv6 4
GRE-IPv4 5 GRE-IPv4 5
GRE-IPv6 6 GRE-IPv6 6
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