Network Working Group L. Xue
Internet-Draft Huawei
Intended status: Informational February 18, 2013
Expires: August 22, 2013
DHCP option for STA Location Information
draft-xue-dhc-location-option-00
Abstract
This document introduces WTP information transported using DHCP. In
this procedure, DHCP snooping is deployed on the WTP node or AC node.
Then the WTP information can be inserted into the extension option of
DHCP message. GW obtain the WTP information of the subscriber
through which the subscriber accesses network.
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 RFC 2119 [RFC2119].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
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This Internet-Draft will expire on August 22, 2013.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Applicability . . . . . . . . . . . . . . . . . . . . . . . . . 5
3. DHCP Operation . . . . . . . . . . . . . . . . . . . . . . . . 6
4. Location Information Option . . . . . . . . . . . . . . . . . . 7
5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 8
6. Security Considerations . . . . . . . . . . . . . . . . . . . . 8
7. References . . . . . . . . . . . . . . . . . . . . . . . . . . 8
7.1. Normative References . . . . . . . . . . . . . . . . . . . 8
7.2. Informative References . . . . . . . . . . . . . . . . . . 8
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 8
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1. Introduction
WLAN (Wireless Local Area Network) features low cost and flexible,
and even high speed wireless data access with open spectrum. So it
is becoming very popular these years. Especially, it is a general
case that currently WLAN is used to supplement cellular (2G/3G/LTE)
network. This provides a good chance for operators to offer
broadband service with less CAPEX.
Traditionally, WLAN consists of WTP and AC device as optional. WTP
is the physical or logical network entity that contains an RF antenna
and wireless physical layer (PHY) to transmit and receive station
traffic for wireless access networks, and then transmit the packet to
the wireline network. It works as media converter. There are two
kinds of WTP in exiting network, defined as standalone WTP and
Controlled WTP. The standalone WTP refers to the WTP in autonomous
WLAN architecture. Here standalone WTP response for all WLAN
functionality, such as encryption/decryption, authentication, etc.
Instead, controlled WTP refers to the WTP in centralized WLAN
architecture. In this case, WTP management and subscriber
authentication are implemented on AC device.
It is possible that AC isn't intelligent enough to aggregate all the
WLAN critical functions in one, because the AC device is always
enterprise device instead of carrier device. It is costly in large-
scale intelligent AC deployment, also it is challenge for operators.
So it is a popular scenario to split the authentication function from
AC to Gateway(GW), which is the existing authentication gateway for
other service, such as PPP, etc. This enables a better environment
that diminishes the software and hardware upgrade for operators,
shown in figure 1.
+------+
| |
| AC |
| |
+--+---+
|
|
|
+------+ +------+ +--+---+ /-------\
| | | | | | | |
| STA | /-/ | WTP +--------------+ GW +----+ Service |
| | | | | | | |
+------+ +------+ +------+ \-------/
Figure 1 Centralized WLAN Architecture
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However, some issues arise meanwhile if the authentication moved out
from the AC. One of the issues is that Gateway can't obtain the WTP
information(MAC address, etc) because the WTP management function is
located in AC device. The challenge is that WTP information for the
subscriber is actually appreciated for operators. For example,
subscriber's location information (WTP information ) is required in
the charging bill, in order to the collect statistical parameter or
push advertisement to special WTP, or locate the fault exactly, etc.
This document introduces WTP information transported using DHCP. In
this procedure, DHCP snooping is deployed on the WTP node or AC node.
The DHCP snooping node will recognize the DHCP packets and insert the
WTP information into the extension option of DHCP messages . Then
the subscriber's WTP information is transported. GW obtains the WTP
information through which the subscriber access network. If the WTP
information is MAC address, the subscriber location information will
be obtained by GW. Also GW can inform location information to AAA
server, etc. The operators can use this information to achieve some
management, such as locating fault, push advertisement to special
WTP, etc.
1.1. Terminology
This document uses the following terms.
Wireless Termination Point (WTP)
The physical or logical network entity that contains an RF antenna
and wireless physical layer (PHY) to transmit and receive station
traffic for wireless access networks. This definition has the same
meaning used in [RFC4118]. It also called AP.
Access Controller (AC)
The network entity that provides WTP access to the network
infrastructure in the data plane, control plane, management plane, or
a combination therein, as defined in[RFC4118].
Also the terms used in this document are accordant with the
terminologies in [RFC2131].
Gateway (GW)
A device in operator access network, who can charge the subscriber
authentication. It maybe BRAS (Broadband Remote Access Server) or
BNG (Broadband Network Gateway).
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2. Applicability
This specification applies when layer 2 network is deployed between
WTP and GW or layer 2 network is deployed between WTP and AC. In
these cases, the procedure specified in this document should be used
for WTP information transmission. It occurs for two scenarios.
o AC is deployed as a standalone node, which is WTP management
device and doesn't transport the traffic for the subscriber at
all, shown in figure 2.
o AC is involved in the subscriber traffic transport, shown in
figure 3. The subscriber traffic can be transported via Layer 2
network or CAPWAP tunnel between WTP and AC. Note:the layer 2
connection is assumed between AC and GW.
+------+
| |
| AC |
| |
+--+---+
|
|
|
+------+ +------+ Traffic for STA+--+---+ /-------\
| | | +----------------+ | | |
| STA | /-/ | WTP +----------------+ GW +----+ Service |
| | | | Layer 2 | | | |
+------+ +------+ +------+ \-------/
Figure 2 Traffic bypass AC
Traffic
+------+ +------+ for STA +------+ +------+ /-------\
| | | +-----------+ | | | | |
| STA | /-/ | WTP +-----------+ AC +---+ GW +--+ Service |
| | | | Layer 2/ | | | | | |
+------+ +------+ CAPWAP TUN+------+ +------+ \-------/
Figure 3 Traffic through AC
Moreover, this specification applies when DHCP snooping mentioned in
[SAVI-DHCP] is deployed on WTP or AC node. Any DHCP protocol agent
and server that implements the mechanism described in this document
assume that they follow the DHCP general procedure [RFC2131].
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3. DHCP Operation
The DHCP procedure when DHCP snooping is deployed on WTP/AC node is
described in this section. Take the first scenario shown in figure 2
for example. The operation for the WTP information transport is
shown in figure 4.
+------+
| |
| AC |
| |
+--+---+
+------+ +------+ Traffic for STA+--+---+ +------+
| | | +----------------+ | | |
| STA | /-/ | WTP +----------------+ GW | | AAA |
| | | | Layer 2 | | | |
+------+ +------+ +------+ +------+
| | | |
| 1 DHCP snooping | |
| | | |
| 2 DHCP Discover | | |
+---------------->| | |
| 3a Insert WTP info | |
| into DHCP message | |
| | | |
| |DHCP Discover(WTP MAC)| |
| +--------------------->| |
| DHCP offer | |
|<----------------+----------------------+ |
| DHCP Request | | |
+---------------->| | |
| 3b Insert|WTP info | |
| into DHCP message | |
| | | |
| |DHCP Request(WTP MAC) | |
| +--------------------->| |
| | 4 GW obtain WTP info |
| DHCP ACK via DHCP option |
|<----------------+----------------------+ |
| Authentication Procedure | |
|<----------------+--------------------->| 5 WTP info |
| | | via RADIUS |
| | +------------------->|
| | | |
Figure 4 DHCP Operation
1 DHCP snooping is deployed on WTP node. Then WTP node can capture
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the DHCP message.
2 STA initiates DHCP procedure via DHCP discovery message.
3 WTP recognizes the DHCP packets and inserts the WTP
information,such as MAC address into the new DHCP option of DHCP
message, both DHCP Discovery and DHCP Request .
4 The WTP information for the subscriber can be obtained by GW via
DHCP option. GW treats this information as subscriber profile.
5 After IP address assignment, the authentication procedure is
initiated. During the authentication procedure, WTP info can be
transported to AAA service via RADIUS message. The operators can use
this information to achieve some management, such as locating fault,
push advertisement to special WTP, etc. This step is out the scope
of this specification.
As the other scenario shown in figure 3, AC is responsible to
transport subscriber traffic from AP to GW. Because AC manages and
configures WTP, it is assumed that AC has record the WTP MAC address.
So here, the DHCP snooping function is deployed on AC node, and the
procedure is same as shown in figure 4.
4. Location Information Option
This documents defines a new option called Location Information
Option. It is an optional option for the specific subscriber's WTP
information transport. The format of the Location Information Option
is:
0 1 2 3 4
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| code | Length | WTP information |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| WTP information (cont) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5 Location Information Option
The code is recommended to the value still unassigned. In this
document, value 140 is suggested.
The length is 6, while the WTP information field is just filled in
WTP MAC address.
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5. IANA Considerations
TBD
6. Security Considerations
TBD
7. References
7.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2131] Droms, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.
[RFC2132] Alexander, S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.
[RFC3369] Housley, R., "Cryptographic Message Syntax (CMS)",
RFC 3369, August 2002.
[RFC4118] Yang, L., Zerfos, P., and E. Sadot, "Architecture Taxonomy
for Control and Provisioning of Wireless Access Points
(CAPWAP)", RFC 4118, June 2005.
7.2. Informative References
[SAVI-DHCP]
"draft-ietf-savi-dhcp", June 2012.
Author's Address
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
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