wdiff draft-huang-dhc-multiple-relay-agents-option-00.txt draft-huang-dhc-multiple-relay-agents-option-01.txt

DHC Lu Working Group L. Huang
Internet Draft Hui
Internet-Draft H. Deng
Intended status: Informational China Mobile
Expires: April 18, September 5, 2010 March 4, 2010 October 19, 2009

DHCP option including Multiple Relay Agents' Information

draft-huang-dhc-multiple-relay-agents-option-00.txt
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

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Abstract

RFC 3046 allows only Code Components extracted from this document must
include Simplified BSD License text as described in Section 4.e of
the first Relay Agent to append Relay Agent
Information option. In some networks, both Layer 2 Relay Agents Trust Legal Provisions and
Layer 3 Relay Agents are deployed and their information is necessary
for DHCP packets forwarding and DHCP server's policy designing
described provided without warranty as [4]. This document defines a DHCP option which can
contain multiple relay agents' information and describes how it works.
described in the BSD License.

Table of Contents

1. Introduction......................................... 2 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. DHCP option including Multiple Relay Agents' Information .... 3 . . . 4
2.1. Mechanism....................................... 3
2.2. Format ......................................... . . . . . . . . . . . . . . . . . . . . . . . . . . 4
2.2. Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. Security Considerations................................ 5 Considerations . . . . . . . . . . . . . . . . . . . . 6
4. IANA Considerations................................... 5 Considerations . . . . . . . . . . . . . . . . . . . . . . 7
5. References.......................................... 5
5.1. Normative References.............................. 5
5.2. Informative References............................ 5
Author's Addresses...................................... 6 References . . . . . . . . . . . . . . . . . . . . 8
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 9

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 verbatim to the relay agent in server-
to-client 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 [4], [I-D.huang-dhc-relay-ps], multiply relay
agents need to insert more information into the same DHCP message.
This document defines a
DHCP new sub-options for Relay Agent Information
option which can contain multiple relay agents' information (option 82) and describes how it works. multiple relay agents add their
information into option 82.

2. DHCP option including Multiple Relay Agents' Information

2.1. Mechanism

This option is organized as Format

+-------+-----+-----+
|Code(x)| Len |Value|
+-------+-----+-----+

Sub-option x: Agent ID. Describe a single DHCP option that contains one or
more sub-options. Each relay unique identifier for the agent can
who insert a this set of sub-options to
convey its Information. sub-options.

+-------+-------+
|Code(y)| Len(0)|
+-------+-------+

Sub-option y: Identify the end of information of one device.

2.2. Mechanism

As shown in figure 1, above figure, it's a most popular network scenario where
option including Multiple Relay Agents' Information is necessary.
Based on the demand of the new Relay Agent Information option as [4],
this option works [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 any
options defined in this document. option
82. So it inserts a new an option in
which a set of sub-options convey the layer 2 relay agent's
necessary information. 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 a relay agent information an option 82. Firstly it adds an sub-option
y defined in this document. So it just insert a set of sub-options section 2.2 into the existing option to convey 82 following sub-
options added by layer 2 agent. And then it adds its own necessary information. 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 as normal and could carry out
flexible IP assigning or other policies based on the information of
option defined 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 its set of sub-options.

6. 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. Because there is no other agent's information left in the
option, so in this case layer Layer 2 relay agent delete deletes the whole option 82 before
forwarding the packet.

2.2. Format

Option format:

+-------+-----+-----+
|Code(x)| Len |Value|
+-------+-----+-----+

This option use a new DHCP option code "x".

Value:

+-----------+-----------+-----------+-----------+
|sub-option1|sub-option2|sub-option3|sub-option4|
+-+--+------+-+--+------+-+--+------+-+--+------+
|1|N1|value1|2|N2|value2|3|N3|value3|4|N4|value4|->a Set of sub-options
+-+--+------+-+--+------+-+--+------+-+--+------+
/ ... \
| Multiple sets of sub-options |
\ ... /
+-+--+------+-+--+------+-+--+------+-+--+------+
|1|N1|value1|2|N2|value2|3|N3|value3|4|N4|value4|
+-+--+------+-+--+------+-+--+------+-+--+------+

Sub-option1

Agent level. Describe the order of agent who insert this set of
sub-options. For example, in the case of figure 1, layer 2

If there are more relay
agent's level is 1 because it is the closest agent to the client agents between Layer 2 and it will be the first Layer 3 relay
agent who insert or between Layer 3 relay agent information.

Sub-option2

Agent ID. Describe a unique identifier for and DHCP server, the agent who insert
this set of sub-options.

Sub-option3
IP address. Describe IP address of third and
the agent who insert this set
of sub-options. For a pure layer 2 agent, this field following relay agents could be
0.0.0.0.

Sub-option4

Downstream interface. Describe only add their agent ID sub-
option(x), circuit ID sub-option and end ID sub-option(y) into the receiving interface of
existing option 82 before forwarding the
DHCP discovery packet upward.
The processing of the agent who insert this set of sub-options. replay packet from DHCP server to client is similar
as above.

3. Security Considerations

This document doesn't propose any new protocol.

4. IANA Considerations

This document requires a new number numbers for DHCP option sub-option code x and y
described in section 2.2. 2.1.

5. Informative References

5.1. Normative References

[1] R.

[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, Bucknell University, R., "Dynamic Host Configuration Protocol",
RFC 2131, March 1997.

[2] S.

[RFC2132] Alexander, Silicon Graphics, Inc., S. and R. Droms, "DHCP Options and BOOTP Vendor
Extensions", RFC 2132, March 1997.

[3] M.

[RFC3046] Patrick, Motorola BCS, M., "DHCP Relay Agent Information Option",
RFC 3046, January 2001.

5.2. Informative References

[4] L. Huang, H. Deng, China Mobile, "Problem Statement for DHCP Relay
Agent", draft-huang-dhc-relay-ps-00, July 2009.

Author's

Authors' Addresses

Lu Huang
China Mobile
53A,Xibianmennei Ave.,
Xuanwu District,
Unit2, 28 Xuanwumenxi Ave,Xuanwu District
Beijing 100053
China

Email: huanglu@chinamobile.com

Hui Deng
China Mobile
53A,Xibianmennei Ave.,
Xuanwu District,
Unit2, 28 Xuanwumenxi Ave,Xuanwu District
Beijing 100053
China

Email: denghui02@gmail.com denghui@chinamobile.com