Internet Engineering Task Force (IETF) C. Shao

Internet Engineering Task Force (IETF) C. Shao
Request for Comments: 7494 H. Deng
Category: Standards Track China Mobile
ISSN: 2070-1721 R. Pazhyannur
Cisco Systems
F. Bari
AT&T
R. Zhang
China Telecom
S. Matsushima
SoftBank Telecom
April 2015

IEEE 802.11 Medium Access Control (MAC) Profile for Control and
Provisioning of Wireless Access Points (CAPWAP)

Abstract

The Control and Provisioning of Wireless Access Points (CAPWAP)
protocol binding for IEEE 802.11 defines two Medium Access Control
(MAC) modes for IEEE 802.11 Wireless Transmission Points (WTPs):
Split and Local MAC. In the Split MAC mode, the partitioning of
encryption/decryption functions is not clearly defined. In the Split
MAC mode description, IEEE 802.11 encryption is specified as located
in either the Access Controller (AC) or the WTP, with no clear way
for the AC to inform the WTP of where the encryption functionality
should be located. This leads to interoperability issues, especially
when the AC and WTP come from different vendors. To prevent
interoperability issues, this specification defines an IEEE 802.11
MAC Profile message element in which each profile specifies an
unambiguous division of encryption functionality between the WTP and
AC.

Status of This Memo

This is an Internet Standards Track document.

This document is a product of the Internet Engineering Task Force
(IETF). It represents the consensus of the IETF community. It has
received public review and has been approved for publication by the
Internet Engineering Steering Group (IESG). Further information on
Internet Standards is available in Section 2 of RFC 5741.

Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
http://www.rfc-editor.org/info/rfc7494.

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RFC 7494 CAPWAP MAC Profile April 2015

Copyright Notice

Copyright (c) 2015 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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the Trust Legal Provisions and are provided without warranty as
described in the Simplified BSD License.

Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. IEEE MAC Profile Descriptions . . . . . . . . . . . . . . . . 5
2.1. Split MAC with WTP Encryption . . . . . . . . . . . . . . 5
2.2. Split MAC with AC Encryption . . . . . . . . . . . . . . 6
2.3. IEEE 802.11 MAC Profile Frame Exchange . . . . . . . . . 8
3. MAC Profile Message Element Definitions . . . . . . . . . . . 8
3.1. IEEE 802.11 Supported MAC Profiles . . . . . . . . . . . 8
3.2. IEEE 802.11 MAC Profile . . . . . . . . . . . . . . . . . 9
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
6. References . . . . . . . . . . . . . . . . . . . . . . . . . 11
6.1. Normative References . . . . . . . . . . . . . . . . . . 11
6.2. Informative References . . . . . . . . . . . . . . . . . 11
Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . . 12
Contributors . . . . . . . . . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12

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RFC 7494 CAPWAP MAC Profile April 2015

1. Introduction

The CAPWAP protocol supports two MAC modes of operation: Split and
Local MAC, as described in [RFC5415] and [RFC5416]. However, there
are MAC functions that have not been clearly defined. For example,
IEEE 802.11 [IEEE.802.11] encryption is specified as located in
either the AC or the WTP with no clear way to negotiate where it
should be located. Because different vendors have different
definitions of the MAC mode, many MAC-layer functions are mapped
differently to either the WTP or the AC by different vendors.
Therefore, depending upon the vendor, the operators in their
deployments have to perform different configurations based on
implementation of the two modes by their vendor. If there is no
clear specification, then operators will experience interoperability
issues with WTPs and ACs from different vendors.

Figure 1 from [RFC5416] illustrates how some functions are processed
in different places in the Local MAC and Split MAC mode.
Specifically, note that in the Split MAC mode, the IEEE 802.11
encryption/decryption is specified as WTP/AC, implying that it could
be at either location. This is not an issue with Local MAC because
encryption is always at the WTP.

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RFC 7494 CAPWAP MAC Profile April 2015

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Functions | Local MAC | Split MAC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Distribution Service | WTP/AC | AC |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Integration Service | WTP | AC |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Beacon Generation | WTP | WTP |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Probe Response Generation| WTP | WTP |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Function |Power Mgmt/ | WTP | WTP |
+ |Packet Buffering | | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Fragmentation/ | WTP | WTP/AC |
+ |Defragmentation | | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Assoc/Disassoc/Reassoc | WTP/AC | AC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Classifying | WTP | AC |
+ IEEE +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 802.11 QoS |Scheduling | WTP | WTP/AC |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Queuing | WTP | WTP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |IEEE 802.1X/EAP | AC | AC |
+ IEEE +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 802.11 RSN |RSNA Key Management | AC | AC |
+ (WPA2) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |IEEE 802.11 | WTP | WTP/AC |
+ |Encryption/Decryption | | |
|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Note:
RSN - Robust Security Network
RSNA - Robust Security Network Association
WPA2 - Wi-Fi Protected Access 2

Figure 1: Functions in Local MAC and Split MAC

To solve this problem, this specification introduces the IEEE 802.11
MAC Profile. The IEEE 802.11 MAC Profile unambiguously specifies
where the various MAC functionalities should be located.

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RFC 7494 CAPWAP MAC Profile April 2015

2. IEEE MAC Profile Descriptions

A IEEE 802.11 MAC Profile refers to a description of how the MAC
functionality is split between the WTP and AC shown in Figure 1.

2.1. Split MAC with WTP Encryption

The functional split for the Split MAC with WTP encryption is
provided in Figure 2. This profile is similar to the Split MAC
description in [RFC5416], except that IEEE 802.11 encryption/
decryption is at the WTP. Note that fragmentation is always done at
the same entity as the encryption. Consequently, in this profile
fragmentation/defragmentation is also done only at the WTP. Note
that scheduling functionality is denoted as WTP/AC. As explained in
[RFC5416], this means that the admission control component of IEEE
802.11 resides on the AC; the real-time scheduling and queuing
functions are on the WTP.

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+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Functions | Profile |
| | 0 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Distribution Service | AC |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Integration Service | AC |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Beacon Generation | WTP |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Probe Response Generation| WTP |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Function |Power Mgmt/ | WTP |
+ |Packet Buffering | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Fragmentation/ | WTP |
+ |Defragmentation | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Assoc/Disassoc/Reassoc | AC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Classifying | AC |
+ IEEE +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 802.11 QoS |Scheduling | WTP/AC |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Queuing | WTP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |IEEE 802.1X/EAP | AC |
+ IEEE +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 802.11 RSN |RSNA Key Management | AC |
+ (WPA2) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |IEEE 802.11 | WTP |
+ |Encryption/Decryption | |
|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Note:
EAP - Extensible Authentication Protocol

Figure 2: Functions in Split MAC with WTP Encryption

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2.2. Split MAC with AC Encryption

The functional split for the Split MAC with AC encryption is provided
in Figure 3. This profile is similar to the Split MAC in [RFC5416],
except that IEEE 802.11 encryption/decryption is at the AC. Since
fragmentation is always done at the same entity as the encryption, in
this profile, AC does fragmentation/defragmentation.

+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Functions | Profile |
| | 1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Distribution Service | AC |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Integration Service | AC |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Beacon Generation | WTP |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Probe Response Generation| WTP |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Function |Power Mgmt/ | WTP |
+ |Packet Buffering | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Fragmentation/ | AC |
+ |Defragmentation | |
| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Assoc/Disassoc/Reassoc | AC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Classifying | AC |
+ IEEE +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 802.11 QoS |Scheduling | WTP |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Queuing | WTP |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |IEEE 802.1X/EAP | AC |
+ IEEE +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| 802.11 RSN |RSNA Key Management | AC |
+ (WPA2) +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |IEEE 802.11 | AC |
+ |Encryption/Decryption | |
|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Figure 3: Functions in Split MAC with AC encryption

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RFC 7494 CAPWAP MAC Profile April 2015

2.3. IEEE 802.11 MAC Profile Frame Exchange

An example of message exchange using the IEEE 802.11 MAC Profile
message element is shown in Figure 4. The WTP informs the AC of the
various MAC Profiles it supports. This happens in either a Discovery
Request message or the Join Request message. The AC determines the
appropriate profile and configures the WTP with the profile while
configuring the WLAN.

+-+-+-+-+-+-+ +-+-+-+-+-+-+
| WTP | | AC |
+-+-+-+-+-+-+ +-+-+-+-+-+-+
|Join Request[Supported IEEE 802.11 |
| MAC Profiles ] |
|---------------------------------------->|
| |
|Join Response |
|<----------------------------------------|
| |
|IEEE 802.11 WLAN Config. Request [ |
| IEEE 802.11 Add WLAN, |
| IEEE 802.11 MAC Profile |
| ] |
|<----------------------------------------|
| |
|IEEE 802.11 WLAN Config. Response |
|---------------------------------------->|

Figure 4: Message Exchange for Negotiating MAC Profiles

3. MAC Profile Message Element Definitions

3.1. IEEE 802.11 Supported MAC Profiles

The IEEE 802.11 Supported MAC Profile message element allows the WTP
to communicate the profiles it supports. The Discovery Request
message, Primary Discovery Request message, and Join Request message
may include one such message element.

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
+=+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-
| Num_Profiles | Profile_1 | Profile_[2..N]..
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-

Figure 5: IEEE 802.11 Supported MAC Profiles

o Type: 1060 for IEEE 802.11 Supported MAC Profiles

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o Num_Profiles >=1: This refers to the number of profiles present in
this message element. There must be at least one profile.

o Profile: Each profile is identified by a value specified in
Section 3.2.

3.2. IEEE 802.11 MAC Profile

The IEEE 802.11 MAC Profile message element allows the AC to select a
profile. This message element may be provided along with the IEEE
802.11 ADD WLAN message element while configuring a WLAN on the WTP.

0 1 2 3 4 5 6 7
+=+-+-+-+-+-+-+-+
| Profile |
+-+-+-+-+-+-+-+-+

Figure 6: IEEE 802.11 MAC Profile

o Type: 1061 for IEEE 802.11 MAC Profile

o Profile: The profile is identified by a value as given below

* 0: This refers to the IEEE 802.11 Split MAC Profile with WTP
encryption

* 1: This refers to the IEEE 802.11 Split MAC Profile with AC
encryption

4. Security Considerations

This document does not introduce any new security risks compared to
[RFC5416]. The negotiation messages between the WTP and AC have
origin authentication and data integrity. As a result, an attacker
cannot interfere with the messages to force a less-secure mode
choice. The security considerations described in [RFC5416] apply
here as well.

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5. IANA Considerations

The following IANA actions have been completed.

o This specification defines two new message elements: IEEE 802.11
Supported MAC Profiles (described in Section 3.1) and the IEEE
802.11 MAC Profile (described in Section 3.2). These elements
have been registered in the existing "CAPWAP Message Element Type"
registry, defined in [RFC5415].

CAPWAP Protocol Message Element Type Value
IEEE 802.11 Supported MAC Profiles 1060
IEEE 802.11 MAC Profile 1061

o The IEEE 802.11 Supported MAC Profiles message element and IEEE
802.11 MAC Profile message element include a Profile field (as
defined in Section 3.2). The Profile field in the IEEE 802.11
Supported MAC Profiles denotes the MAC Profiles supported by the
WTP. The Profile field in the IEEE 802.11 MAC Profile denotes the
MAC Profile assigned to the WTP. The namespace for the field is 8
bits (0-255). This specification defines two values: zero (0) and
one (1) as described below. The remaining values (2-255) are
controlled and maintained by IANA, and the registration procedure
is Expert Review [RFC5226]. IANA has created a new subregistry
called "IEEE 802.11 Split MAC Profile" under the existing registry
"Control And Provisioning of Wireless Access Points (CAPWAP)
Parameters". The registry format is given below.

Profile Type Value Reference
Split MAC with WTP encryption 0 RFC 7494
Split MAC with AC encryption 1 RFC 7494

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RFC 7494 CAPWAP MAC Profile April 2015

6. References

6.1. Normative References

[IEEE.802.11]
IEEE, "IEEE Standard for Information Technology -
Telecommunications and information exchange between
systems - Local and metropolitan area networks - Specific
requirements Part 11: Wireless LAN Medium Access Control
(MAC) and Physical Layer (PHY) Specifications", IEEE Std
802.11-2012, March 2012,
<http://standards.ieee.org/about/get/802/802.11.html>.

[RFC5415] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
Ed., "Control And Provisioning of Wireless Access Points
(CAPWAP) Protocol Specification", RFC 5415, March 2009,
<http://www.rfc-editor.org/info/rfc5415>.

[RFC5416] Calhoun, P., Ed., Montemurro, M., Ed., and D. Stanley,
Ed., "Control and Provisioning of Wireless Access Points
(CAPWAP) Protocol Binding for IEEE 802.11", RFC 5416,
March 2009, <http://www.rfc-editor.org/info/rfc5416>.

6.2. Informative References

[RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an
IANA Considerations Section in RFCs", BCP 26, RFC 5226,
May 2008, <http://www.rfc-editor.org/info/rfc5226>.

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RFC 7494 CAPWAP MAC Profile April 2015

Acknowledgments

The authors are grateful for extremely valuable suggestions from
Dorothy Stanley in developing this specification.

Guidance from the management team -- Melinda Shore, Scott Bradner,
Chris Liljenstolpe, Benoit Claise, Joel Jaeggli, and Dan Romascanu --
is highly appreciated.

Contributors

Yifan Chen <[email protected]>

Naibao Zhou <[email protected]>

Authors' Addresses

Chunju Shao
China Mobile
No.32 Xuanwumen West Street
Beijing 100053
China

EMail: [email protected]

Hui Deng
China Mobile
No.32 Xuanwumen West Street
Beijing 100053
China

EMail: [email protected]

Rajesh S. Pazhyannur
Cisco Systems
170 West Tasman Drive
San Jose, CA 95134
United States

EMail: [email protected]

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RFC 7494 CAPWAP MAC Profile April 2015

Farooq Bari
AT&T
7277 164th Ave NE
Redmond, WA 98052
United States

EMail: [email protected]

Rong Zhang
China Telecom
No.109 Zhongshandadao avenue
Guangzhou 510630
China

EMail: [email protected]

Satoru Matsushima
SoftBank Telecom
1-9-1 Higashi-Shinbashi, Munato-ku
Tokyo
Japan

EMail: [email protected]

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