Internet Engineering Task Force Richard Johnson
Internet Draft Ralph Droms
Expiration: December 2003 Mark Stapp
File: draft-ietf-dhc-subscriber-id-01.txt Theyn Palaniappan
Cisco Systems, Inc.
DHCP Subscriber ID Suboption for the DHCP Relay Agent Option
<draft-ietf-dhc-subscriber-id-01.txt>
June 4, 2003
Status of this Memo
This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026.
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Copyright Notice
Copyright (C) The Internet Society (2002). All Rights Reserved.
Abstract
This memo defines a new DHCP Relay Suboption for passing an arbitrary
number of bytes defining what will be called the "Subscriber ID".
This value is simply defined as an array of bytes and can be
interpreted in any form by the DHCP server. Its intended purpose is
to give additional information which the DHCP server can use in
address allocation.
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Internet Draft DHCP Subscriber ID Suboption June 2003
1.0 Introduction
The Remote-ID sub-option of the relay agent information option (also
called option-82) are calculated based on network resources like ip-
address of the NSAP, atm VP, atm VC. As a result, when moving a link
to a different port, a different value is calculated. This holds true
for every subscriber that is connected with the particular link and
the links are connected to different service providers. When the
subscriber moves, each Service Provider has to be informed of the
change and all the Service Providers have to change their DHCP [2]
settings for the affected customers at the same time.
When the service delivered has not changed, every move involves
administrative changes in Service Providers environment causing delay
in the customer service.
Therefore an additional Relay Suboption for the DHCP Relay Agent
option is being introduced, to add a configurable hexadecimal value
to provide this information. This unique id will enable the Service
Provider to identify a subscriber and to assign/activate subscriber
specific actions, e.g. assignment of host IP address, subnet mask,
DNS, trigger accounting, etc. This specific field is de-coupled from
the NAS-IP, since the users could be able to move from NAS
termination points. Thus when a subscriber moves from one NAS to
another, this would not result in a configuration change on the side
of the DHCP server of the Service Provider.
This memo describes a new DHCP Relay suboption which would carry a
"Subscriber ID" value. The value is simply an array of bytes which
can be interpreted by the DHCP server in whatever manner wanted. The
value can be a character string giving the name of the subscriber,
four bytes interpreted as a big endian unsigned integer giving the
number of the subscriber, a string of hex digits giving the
subscriber ID, or whatever is needed. The precise definition of the
bytes is left to the implementation and field use.
1.1 Conventions
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 [1].
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Internet Draft DHCP Subscriber ID Suboption June 2003
1.2 Terminology
VC Virtual Channel. Logical circuit created to ensure reliable
communication between two network devices. A virtual circuit is
defined by a VPI/VCI pair, and can be either permanent (PVC) or
switched (SVC). Virtual circuits are used in Frame Relay and
X.25. In ATM, a virtual circuit is called a virtual channel.
VP Virtual Path. Logical grouping of virtual circuits that connect
two sites.
NAS Network Access Server. Platform (or collection of platforms)
that interfaces between the packet world (for example, the
Internet) and the circuit world (for example, the PSTN).
NSAP Network Service Access Point. Network addresses, as specified by
ISO. An NSAP is the point at which OSI network service is made
available to a transport layer (Layer 4) entity.
PSTN Public Switched Telephone Network. General term referring to the
variety of telephone networks and services in place worldwide.
2.0 DHCP Relay Information Suboption Definition
The Subscriber ID is a DHCP Relay Information Suboption. The exact
option code value is TBD. The suboption takes the same form as other
Relay Information Suboptions:
Code Len Subscribe ID octets
+-----+-----+------+-----+-----+---
| TBD | n | v1 | v2 | v3 | ...
+-----+-----+------+-----+-----+---
The option minimum length (n) is 1.
This option provides the DHCP server additional information upon
which to make a determination of address to be assigned. The DHCP
server, if it is configured to support this option, should use this
information in addition to other options included in the DHCPDISCOVER
packet in order to assign an IP address for the DHCP client.
As per [3], the contents of the entire Relay Agent Option SHALL be
included in all replies by DHCP servers understanding the Relay Agent
Option. There is no special additional processing for this
suboption.
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Internet Draft DHCP Subscriber ID Suboption June 2003
3.0 Security Considerations
Message authentication in DHCP for intradomain use where the out-of-
band exchange of a shared secret is feasible is defined in RFC 3118
[5]. Potential exposures to attack are discussed in section 7 of the
DHCP protocol specification in RFC 2131 [2].
The DHCP Relay Agent option depends on a trusted relationship between
the DHCP relay agent and the server, as described in section 5 of RFC
3046. While the introduction of fraudulent relay-agent options can
be prevented by a perimeter defense that blocks these options unless
the relay agent is trusted, a deeper defense using the authentication
option for relay agent options [4] SHOULD be deployed as well.
4.0 IANA Considerations
IANA has assigned a value of TBD for the DHCP Relay Information
Suboption code described in this document.
5.0 Acknowledgements
This document is the result of work done within Cisco Systems.
Thanks to Ralph Droms, Mark Stapp and Theyn Palaniappan for their
work on this option definition and the other related work for which
this is necessary. Thanks also to Andy Sudduth for his review
comments.
References
[1] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", RFC 2119, BCP 14, March 1997.
[2] Droms, R. "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
[3] Patrick, M., "DHCP Relay Agent Information Option",
RFC 3046, January 2001
[4] Stapp, M. "The Authentication Suboption for the DHCP
Relay Agent Option", draft-ietf-dhc-auth-suboption-00.txt,
June 23, 2002
[5] Droms, R. "Authentication for DHCP Messages", RFC 3118,
June 2001
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Internet Draft DHCP Subscriber ID Suboption June 2003
Author Information:
Richard Johnson
Theyn Palaniappan
Cisco Systems
170 W. Tasman Dr.
San Jose, CA 95134
Phone: (408) 526-4000
EMail: athenmoz@cisco.com
raj@cisco.com
Ralph Droms
Mark Stapp
Cisco Systems
250 Apollo Drive
Chelmsford, MA 01824
Phone: (978) 244-8000
EMail: rdroms@cisco.com
mjs@cisco.com
Copyright Notice
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Internet Draft DHCP Subscriber ID Suboption June 2003
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
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