draft-ietf-opsawg-capwap-hybridmac-03.txt   draft-ietf-opsawg-capwap-hybridmac-04.txt 
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Cisco Systems Cisco Systems
F. Bari F. Bari
AT&T AT&T
R. Zhang R. Zhang
China Telecom China Telecom
S. Matsushima S. Matsushima
SoftBank Telecom SoftBank Telecom
May 5, 2014 May 5, 2014
IEEE 802.11 MAC Profile for CAPWAP IEEE 802.11 MAC Profile for CAPWAP
draft-ietf-opsawg-capwap-hybridmac-03 draft-ietf-opsawg-capwap-hybridmac-04
Abstract Abstract
CAPWAP defines two entities: Wireless Transmission Point (WTP) and CAPWAP defines two entities: Wireless Transmission Point (WTP) and
Access Controller (AC). CAPWAP also defines two MAC (Medium Access Access Controller (AC). CAPWAP also defines two MAC (Medium Access
Control) modes for IEEE 802.11 WTPs: Split and Local MAC . For each Control) modes for IEEE 802.11 WTPs: Split and Local MAC . For each
MAC mode, CAPWAP describes how the MAC functionality is split between MAC mode, CAPWAP describes how the MAC functionality is split between
the WTP and AC. However, certain functions have not been clearly the WTP and AC. However, certain functions have not been clearly
defined. For example in the Split MAC mode description, the IEEE defined. For example in the Split MAC mode description, the IEEE
802.11 encryption is specified as located in either the AC or the WTP 802.11 encryption is specified as located in either the AC or the WTP
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WTP with no clear way to negotiate where it should be located. WTP with no clear way to negotiate where it should be located.
Because different vendors have their own definition of the MAC mode, Because different vendors have their own definition of the MAC mode,
many MAC layer functions are mapped differently to either the WTP or many MAC layer functions are mapped differently to either the WTP or
the AC by different vendors. Therefore, depending upon the vendor, the AC by different vendors. Therefore, depending upon the vendor,
the operators in their deployments have to perform different the operators in their deployments have to perform different
configurations based on implementation of the two modes by their configurations based on implementation of the two modes by their
vendor. If there is no clear specification then operators will vendor. If there is no clear specification then operators will
experience difficulty in interoperating WTPs and ACs from different experience difficulty in interoperating WTPs and ACs from different
vendors. vendors.
Figure 1 quoted from [RFC5416], illustrates how the functions are Figure 1 is quoted from [RFC5416], illustrates how the functions are
processed in different places in the Local MAC and Split MAC mode. processed in different places in the Local MAC and Split MAC mode.
Specifically, note that in the Split MAC mode the IEEE 802.11 Specifically, note that in the Split MAC mode the IEEE 802.11
encryption/decryption is specified as WTP/AC implying that it could encryption/decryption is specified as WTP/AC implying that it could
be at either location. be at either location.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Functions | Local MAC | Split MAC | | Functions | Local MAC | Split MAC |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |Distribution Service | WTP/AC | AC | | |Distribution Service | WTP/AC | AC |
+ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ + +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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2. Conventions used in this document 2. 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].
3. IEEE MAC Profile Descriptions 3. IEEE MAC Profile Descriptions
A IEEE MAC Profile refers to a description of how the MAC A IEEE MAC Profile refers to a description of how the MAC
functionality is split between the WTP and AC shown in Figure 1 functionality is split between the WTP and AC shown in Figure 1.
3.1. Split MAC with WTP encryption 3.1. Split MAC with WTP encryption
The functional split for the Split MAC with WTP encryption is The functional split for the Split MAC with WTP encryption is
provided in Figure 2. This profile is similar to the Split MAC provided in Figure 2. This profile is similar to the Split MAC
description in [RFC5416] except that IEEE 802.11 encryption/ description in [RFC5416] except that IEEE 802.11 encryption/
decryption is at the WTP. Note that fragmentation is always done at decryption is at the WTP. Note that fragmentation is always done at
the same entity as the encryption. Consequently, in this profile the same entity as the encryption. Consequently, in this profile
fragmentation/defragmentation is also done only at the WTP Note that fragmentation/defragmentation is also done only at the WTP Note that
scheduling functionality is denoted as WTP/AC. As explained in scheduling functionality is denoted as WTP/AC. As explained in
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|-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: Functions in Split MAC with AC encryption Figure 3: Functions in Split MAC with AC encryption
3.3. IEEE 802.11 MAC Profile Frame Exchange 3.3. IEEE 802.11 MAC Profile Frame Exchange
An example of message exchange using the IEEE 802.11 MAC Profile 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 message element is shown in Figure 4. The WTP informs the AC of the
various MAC profiles it supports. This happens either in a Discovery various MAC profiles it supports. This happens either in a Discovery
Request message or the Join Request message. The AC determines the Request message or the Join Request message. The AC determines the
appropriate profile and the configures the WTP with the profile while appropriate profile and configures the WTP with the profile while
configuring the WLAN. configuring the WLAN.
+-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+
| WTP | | AC | | WTP | | AC |
+-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+ +-+-+-+-+-+-+
|Join Request[Supported IEEE 802.11 | |Join Request[Supported IEEE 802.11 |
| MAC Profiles ] | | MAC Profiles ] |
|---------------------------------------->| |---------------------------------------->|
| | | |
|Join Response | |Join Response |
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Figure 6: IEEE 802.11 MAC Profile Figure 6: IEEE 802.11 MAC Profile
o Type: TBD for IEEE 802.11 MAC Profile o Type: TBD for IEEE 802.11 MAC Profile
o Profile: The profile is identified by a value as given below o Profile: The profile is identified by a value as given below
* 0: This refers to the Split MAC Profile with WTP encryption * 0: This refers to the Split MAC Profile with WTP encryption
* 1: This refers to the Split MAC Profile with AC encryption * 1: This refers to the Split MAC Profile with AC encryption
5. Security Considerations 5. Security Considerations
This document doesn't specify security risk difference from This document does not introduce any new security risks compared to
[RFC5416]. Please refer to the Security section of [RFC5416] [RFC5416]. The security considerations described in [RFC5416] apply
here as well.
6. IANA Considerations 6. IANA Considerations
This document requires the following IANA actions. This document requires the following IANA actions.
o This specification defines a new message element, IEEE 802.11 o This specification defines a new message element, IEEE 802.11
Supported MAC Profiles. The format of this option is described in Supported MAC Profiles. The format of this option is described in
Section 4.1. This value needs to be registered in the existing Section 4.1. This value needs to be registered in the existing
CAPWAP Message Element Type registry, defined in [RFC5415]. CAPWAP Message Element Type registry, defined in [RFC5415].
o This specification defines a new message element, IEEE 802.11 MAC o This specification defines a new message element, IEEE 802.11 MAC
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