DHC Working Group L. Huang
Internet-Draft H. Deng
Intended status: Informational China Mobile
Expires: September 5, 2010 March 4, 2010
DHCP option including Multiple Relay Agents' Information
draft-huang-dhc-multiple-relay-agents-option-01
Abstract
RFC 3046 allows only the first Relay Agent to append Relay Agent
Information option. In some networks, both Layer 2 Relay Agents and
Layer 3 Relay Agents are deployed and their information is necessary
for DHCP packets forwarding and DHCP server's policy designing
described as [I-D.huang-dhc-relay-ps]. This document defines new
sub-options for Relay Agent Information option (option 82) and
describes how multiple relay agents add their information into option
82.
Status of this Memo
This Internet-Draft is submitted to IETF in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that
other groups may also distribute working documents as Internet-
Drafts.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress."
The list of current Internet-Drafts can be accessed at
http://www.ietf.org/ietf/1id-abstracts.txt.
The list of Internet-Draft Shadow Directories can be accessed at
http://www.ietf.org/shadow.html.
This Internet-Draft will expire on September 5, 2010.
Copyright Notice
Copyright (c) 2010 IETF Trust and the persons identified as the
document authors. All rights reserved.
Huang & Deng Expires September 5, 2010 [Page 1]
Internet-Draft Option including Multiple Agents' Info March 2010
This document is subject to BCP 78 and the IETF Trust's Legal
Provisions Relating to IETF Documents
(http://trustee.ietf.org/license-info) in effect on the date of
publication of this document. Please review these documents
carefully, as they describe your rights and restrictions with respect
to this document. Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the Trust Legal Provisions and are provided without warranty as
described in the BSD License.
Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. DHCP option including Multiple Relay Agents' Information . . . 4
2.1. Format . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Security Considerations . . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . . 7
5. Informative References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9
Huang & Deng Expires September 5, 2010 [Page 2]
Internet-Draft Option including Multiple Agents' Info March 2010
1. Introduction
As defined in RFC 3046, Relay Agent Information option is inserted by
the DHCP relay agent (or downstream network element) when forwarding
client-originated DHCP packets to a DHCP server. Servers recognizing
the Relay Agent Information option may use the information to
implement IP address or other parameter assignment policies. The
DHCP Server echoes the option back to the relay agent in server-to-
client replies, and the relay agent strips the option before
forwarding the reply to the client.
RFC 3046 allows only one agent add its information with option 82.
But in some scenarios as [I-D.huang-dhc-relay-ps], multiply relay
agents need to insert more information into the same DHCP message.
This document defines new sub-options for Relay Agent Information
option (option 82) and describes how multiple relay agents add their
information into option 82.
Huang & Deng Expires September 5, 2010 [Page 3]
Internet-Draft Option including Multiple Agents' Info March 2010
2. DHCP option including Multiple Relay Agents' Information
2.1. Format
+-------+-----+-----+
|Code(x)| Len |Value|
+-------+-----+-----+
Sub-option x: Agent ID. Describe a unique identifier for the agent
who insert this set of sub-options.
+-------+-------+
|Code(y)| Len(0)|
+-------+-------+
Sub-option y: Identify the end of information of one device.
2.2. Mechanism
-------
+-----------+ +-----------+ /// \\\ +------+
+------+ |Layer 2 | |Layer 3 | | | |DHCP |
|Client+--+Relay Agent+--+Relay Agent+--+ Network +--+Server|
+------+ +-----------+ +-----------+ | | +------+
\\\ ///
-------
As shown in above figure, it's a most popular network scenario where
option including Multiple Relay Agents' Information is necessary.
Based on the demand as [I-D.huang-dhc-relay-ps], agents work as
following:
(1) An initiating client sends a DHCP discovery packet.
(2) Layer 2 relay agent receives the discovery packet without option
82. So it inserts an option 82 as [RFC3046]. After that, the
discovery packet is forwarded to the appropriate port.
(3) Layer 3 relay agent receives the discovery packet and check out
that it already contains an option 82. Firstly it adds an sub-option
y defined in section 2.2 into the existing option 82 following sub-
options added by layer 2 agent. And then it adds its agent ID sub-
option(x), circuit ID sub-option and end ID sub-option(y) into the
existing option 82. After that, the discovery packet is forwarded
and reaches DHCP server directly or through a network.
(4) DHCP server handles the discovery packet and could carry out
flexible IP assigning or other policies based on the information of
Huang & Deng Expires September 5, 2010 [Page 4]
Internet-Draft Option including Multiple Agents' Info March 2010
option 82 described in this document. After that DHCP server reply a
DHCP response packet containing the original option 82 carried in the
corresponding discovery packet.
(5) Layer 3 relay agents quickly get the right outgoing interface
based on the information in the option 82 and forward the response
packet after deleting sub-options it added before.
(6) Layer 2 relay agents quickly get the right outgoing interface
based on the information in the option 82 and forward the response
packet. Layer 2 relay agent deletes the whole option 82 before
forwarding the packet.
If there are more relay agents between Layer 2 and Layer 3 relay
agent or between Layer 3 relay agent and DHCP server, the third and
the following relay agents could only add their agent ID sub-
option(x), circuit ID sub-option and end ID sub-option(y) into the
existing option 82 before forwarding the discovery packet upward.
The processing of replay packet from DHCP server to client is similar
as above.
Huang & Deng Expires September 5, 2010 [Page 5]
Internet-Draft Option including Multiple Agents' Info March 2010
3. Security Considerations
This document doesn't propose any new protocol.
Huang & Deng Expires September 5, 2010 [Page 6]
Internet-Draft Option including Multiple Agents' Info March 2010
4. IANA Considerations
This document requires new numbers for sub-option code x and y
described in section 2.1.
Huang & Deng Expires September 5, 2010 [Page 7]
Internet-Draft Option including Multiple Agents' Info March 2010
5. Informative References
[I-D.huang-dhc-relay-ps]
Huang, L., Deng, H., Kurapati, P., and B. Joshi, "Problem
Statement for DHCP Relay Agent",
draft-huang-dhc-relay-ps-00 (work in progress), July 2009.
[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.
[RFC3046] Patrick, M., "DHCP Relay Agent Information Option",
RFC 3046, January 2001.
Huang & Deng Expires September 5, 2010 [Page 8]
Internet-Draft Option including Multiple Agents' Info March 2010
Authors' Addresses
Lu Huang
China Mobile
Unit2, 28 Xuanwumenxi Ave,Xuanwu District
Beijing 100053
China
Email: huanglu@chinamobile.com
Hui Deng
China Mobile
Unit2, 28 Xuanwumenxi Ave,Xuanwu District
Beijing 100053
China
Email: denghui@chinamobile.com
Huang & Deng Expires September 5, 2010 [Page 9]