wdiff draft-shao-capwap-plus-ps-00.txt draft-shao-capwap-plus-ps-01.txt

Network Working Group CJ. Shao
Internet-Draft H. Deng
Intended status: Informational China Mobile
Expires: April 18, 25, 2013 R. Zhang
China Telecom
F. Bari
AT&T Services
October 15, 22, 2012

Enhancement of CAPWAP Problem Statement
draft-shao-capwap-plus-ps-00
draft-shao-capwap-plus-ps-01

Abstract

With the

In recent widely deployment widescale deployments of large public Wifi network, Wi-Fi networks, and
the
in their integration with cellular network. networks EAP based authentication
has been considered as the a good candidate to improve the Wifi making Wi-Fi user
experience similarly seamless similar to the extend of GSM network. Couple of what it has been for cellular users.
A few new functions which could enhance CAPWAP protocol have been raised to
identified in such deployments that can help improve the large scale
carrier grade Wifi network. Wi-Fi networks.

Status of this Memo

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Table of Contents

1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . . 3
3. Supporting EAP authencation in Wifi Wi-Fi network . . . . . . . . . . 3
3.1. Scenario Description . . . . . . . . . . . . . . . . . . . 3
4. The scope Scope of definition of split Split and Local MAC mode . . . . . . . . . . . . . 4
5. 802.11n support . . . . . . . . . . . . . . . . . . . . . . . . 4
6. Channel auto reconfiguration . . . . . . . . . . . . . . . . . 5
7. Power auto reconfiguration . . . . . . . . . . . . . . . . . . 5 6
8. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 6
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 6
11. Normative References . . . . . . . . . . . . . . . . . . . . . 6
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6 7

1. Introduction

Public Wifi service has been paid more attention due

Mobile devices such as smartphones and tablets continue to the lead
growth of
cellular data traffic, this is mainly originated from faster mobile
network and more smart terminals. in internet traffic. It is predcited predicted that such growth will
continue even with the deployment of LTE network. The capacity
and coverage of LTE network still needs the complementation Almost all mobile
devices today are Wi-Fi enabled. Public Wi-Fi services have lately
been paid more attention for that reason to help bring this growth of public
wifi network because Wifi
cellular data traffic to a sustainable level. Wi-Fi spectrum is free, limited free
and globally available. Because of capacity and almost all smart terminal has the Wifi equiped.

Recent coverage issues, LTE
networks will continue to need public Wi-Fi network as a
complementary technology.

Recently industry efforts have been made to let Wifi make Wi-Fi roaming similar to as easy
seamless as legacy it is for cellular GSM network networks by deploying EAP based
authentication
mechanism, and to let mobile to Wifi integration is seamless and
transparent to the customer; mechanism; Toward this two directions, end current CAPWAP protocol
could be enhanced to improve better user experiences. help ease such deployments.

There have been lots a number of propritary proprietary implementations of the
interface between AP Access Point (AP) and Access Controller (AC) and AC
interfaces,
some of them have very strong capability provide capabilities which could be used to improve the wifi
Wi-Fi performance. Once Standard a standard interface is specified, such merits may be not exist, but it benefit the
benefits for operators of standards based deployment with such sacrifice. will outweigh
any benefits of past proprietary solutions.

2. Conventions used in this document

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].

3. Supporting EAP authencation in Wifi Wi-Fi network

Current EAP message is designed to be transmited transmitted in CAPWAP data
plane,
Plane. AC which is in the middle of data path will act as the authenticator to
transmit this EAP message to AAA server, but sometime, server. An operator would
like to let AC may however
prefer to be in the bypass of the data AC for the user plane which could help in order to improve the
performance of AC, AC and allow it can to manage more APs once when the network is
growing. In order to allow AC ACs to be bypassed, bypassed for EAP messages, the capwap
CAPWAP control message could be extended to support EAP messages.

3.1. Scenario Description

The following figure shows where and how the problem arises. In many
operators' network, the
operators networks. The Access Controller is placed remotely at the
central data center. In order to avoid the traffic aggregation at
the AC, the data plane out of the AP is directed to the Access Router
(AR). In this scenario, the CAPWAP-CTL tunnel and CAPWAP-DATA tunnel
are separated from each other.

Because there are no explict explicit message types to support the
encapsulation of EAP packets in the CAPWAP-CTL tunnel, the EAP
messages are tunneled via the CAPWAP-DATA plane to the AR. AR acts
as authenticator in the EAP framework. After authentication, the AR
receives the keying message for the session. But AC is supposed to
delieve
deliver these keying messages to the AP, and AR has no standard
interface to ship them to the AP or the AC. This is unacceptable in
the scenario of EAP-based auto-authentication.
CAPWAP-CTL +--------+
++========+ AC |
// +--------+
//
+-----+// CAPWAP-DATA +--------------+
| AP |===========================| Access Router|
+-----+ +--------------+

Figure 1: Split between CAPWAP-CTL and CAPWAP-DATA Plane

So it is desirable to encapsulate EAP messages in the CAPWAP-CTL
plane, to avoid data aggregation and improve WLAN system scalability.

4. The scope of definition Scope of split Split and Local MAC mode

There are many functions hasn't 3 major categories has been clearly defined whether they
belong to either AP specified by CAPWAP, the first
is about Functions: such as "Distribution Service", "Integration
Service", "Beacon Generation", "Probe Response Generation" "Power
Mgmt/Packet Buffering", "Fragmentation/Defragmentation", and AC in "Assoc/
Disassoc/Reassoc"; the split mode. Operation needs to
configure differently handle second is about QoS, such as, "Classifying",
"Scheduling", and "Queuing"; the various implementation of split MAC
mode. if there third is no clear scope definition of split MAC about RSN (WPA2) such as
"IEEE 802.1X/EAP", "RSNA Key Management", and local
MAC, then operator "IEEE 802.11
Encryption/Decryption". Even Split and Local MAC model has the diffculty optional
implementation, either at AP or AC, this lead to interoperate serious issue about
Interoperation

Proposing a specific mode about all this implementation will help
interoperation among different vendors.

5. 802.11n support

There are a couple of capabilities of 802.11n that need to be
supported by CAPWAP control message such as radio capability, radio
configuration and station information.

IEEE 802.11n standard was published in 2009 and it is an amendment to
the IEEE 802.11-2007 standard to improve network throughput. The
maximum data rate increases to 600Mbit/s physical throughput rate.
In the physical layer, 802.11n use OFDM and MIMO to achive achieve the high
throughput. 802.11n use multiple antennas to form antenna array which
can be dynamically adjusted to imporve improve the signal strength and extend
the coverage.

802.11n support two modes of channel usage: 20MHz mode and 40Mhz
mode.802.11n has a new feature called channel binding. It can bind
two adjacent 20MHz channel to one 40MHz channel to improve the
throughput.If using 40Mhz channel configuration there will be only
one non-overlapping channel in 2.4GHz. In the large scale deployment
scenario, operator need to use 20MHz channel configuration in 2.4GHz
to allow more non-overlapping channels.

In MAC layer, a new feature of 802.11n is Short Guard Interval(GI).
802.11a/g use 800ns guard interval between the adjacent information
symbols. In 802.11n, the GI can be configured to 400nm under good
wireless condition.

Another feature in 802.11 MAC layer is Block ACK. 802.11n can use one
ACK frame to acknowledge several MPDU receiving event.

CAPWAP need to be extended to support the above new 802.11n features.
For example, CAPWAP should allow the access controller to know the
supported 802.11n features and the access controller should be able
to configure the differe different channel binding modes. One possible
solution is to extend the CAPWAP information element for 802.11n.

6. Channel auto reconfiguration

Channel auto reconfiguration could imporve the Wifi Wi-Fi performance,
CAPWAP message could be extended to support this function.

Each channel may provide different quality of service, when WTP
works. WTP can be active or passive scanning and monitoring each
channel, form the report of measurement results to the Access
Controller. WTP can periodically send configure status request to
the AC. According to the current channel quality and other channel
quality scanning report, ACs decide whether modify the channel to be
used, send the configure status response packet to set up a new
channel for the WTP.

7. Power auto reconfiguration

Power auto reconfiguration could imporve improve the Wifi Wi-Fi performance.
CAPWAP message could be extended to achieve following outcome.

o Maximize Spectrum Usage: Real-world Wi-Fi deployments are
depending on the features of shared media. Three channels
available in the 2.4GHz band and 23 channels in the 5GHz band.
Power auto reconfiguration could help these channels be fully
utilized. As the results, clients could be distributed across all
available channels.
o Reduce Interference: when multiple devices attempt to
simutaneously access the same channel at the same time, a co-
channel interference likely happned. It reduces overall
performance of the channel. The reconfiguration via CAPWAP could
efficiently mitigate the interference. That is essential to
proper network operation
o Optimize Coverage: Simply increasing AP power may not help to
maximize converage because it creates an unbalanced condition in
which more distantly located clients may perforIm poorly due to
their lower transmit output power. The power reconfiguration
could achieve a balanced environment, where configuration could
ensure that coverage is uniform and adequate throughout the
service area.

8. Security Considerations

9. IANA Considerations

None

10. Contributors

Yifan Chen chenyifan@chinamobile.com

Bocun Deng 13316090701@189.cn

Satoru Matsushima satoru.matsushima@tm.softbank.co.jp

11. Normative References

[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

[RFC4564] Govindan, S., Cheng, H., Yao, ZH., Zhou, WH., and L. Yang,
"Objectives for Control and Provisioning of Wireless
Access Points (CAPWAP)", RFC 4564, July 2006.

[RFC5415] Calhoun, P., Montemurro, M., and D. Stanley, "Control And
Provisioning of Wireless Access Points (CAPWAP) Protocol
Specification", RFC 5415, March 2009.

Authors' Addresses

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

Email: shaochunju@chinamobile.com

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

Email: denghui@chinamobile.com

Rong Zhang
China Telecom
No.109 Zhongshandadao avenue
Tianhe District,
Guangzhou 510630
China

Email: zhangr@gsta.com
Farooq Bari
AT&T Services
7277 164th Avenue NE
Redmond
US

Email: farooq.bari@att.com