Generalized UDP Source Port for DHCP Relay
draft-ietf-dhc-relay-port-07

Document Type Active Internet-Draft (dhc WG)
Last updated 2017-11-13 (latest revision 2017-10-27)
Replaces draft-shen-dhc-client-port
Stream IETF
Intended RFC status Proposed Standard
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Stream WG state Submitted to IESG for Publication (wg milestone: Jun 2017 - Submit draft-ietf-dh... )
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IESG IESG state Waiting for Writeup
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Needs 8 more YES or NO OBJECTION positions to pass.
Responsible AD Suresh Krishnan
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Networking Working Group                                         N. Shen
Internet-Draft                                                   E. Chen
Intended status: Standards Track                           Cisco Systems
Expires: April 30, 2018                                 October 27, 2017

               Generalized UDP Source Port for DHCP Relay
                      draft-ietf-dhc-relay-port-07

Abstract

   This document proposes an extension to the DHCP protocols that allows
   a relay agent to use any available source port for upstream
   communications, and to include a DHCP option that can be used to
   statelessly route responses back to the appropriate source port on
   downstream communications.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
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   This Internet-Draft will expire on April 30, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
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   (http://trustee.ietf.org/license-info) in effect on the date of
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   described in the Simplified BSD License.

Shen & Chen              Expires April 30, 2018                 [Page 1]
Internet-Draft           DHCP Relay Source Port             October 2017

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Changes to DHCP Specifications  . . . . . . . . . . . . . . .   3
     3.1.  Changes to DHCPv4 in RFC 2131 . . . . . . . . . . . . . .   3
     3.2.  Changes to DHCPv6 in RFC 3315 . . . . . . . . . . . . . .   4
   4.  Relay Source Port Sub-option and Option . . . . . . . . . . .   4
     4.1.  Source Port Sub-option for DHCPv4 . . . . . . . . . . . .   4
     4.2.  Relay Source Port Option for DHCPv6 . . . . . . . . . . .   5
   5.  Relay Agent and Server Behavior . . . . . . . . . . . . . . .   6
     5.1.  DHCPv4  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     5.2.  DHCPv6  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     5.3.  Compatibility . . . . . . . . . . . . . . . . . . . . . .   7
     5.4.  Deployment Considerations . . . . . . . . . . . . . . . .   7
   6.  An IPv6 Cascaded Relay Example  . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   9
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   9
   10. Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10

1.  Introduction

   RFC 2131 [RFC2131] and RFC 3315 [RFC3315] specify the use of UDP as
   the transport protocol for DHCP.  They also define both the server
   side and client side port numbers.  The IPv4 server port is UDP
   number (67) and the client port is UDP number (68); for IPv6 the
   server port is (546) and the client port is (547).

   The fixed UDP port combinations for the DHCP protocol scheme creates
   challenges in certain DHCP relay operations.  For instance, in a
   large scale DHCP relay implementation on a single switch node, the
   DHCP relay functionality may be partitioned among multiple relay
   processes.  All these DHCP relay processes may share the same IP
   address of the switch node.  If the UDP source port has to be a fixed
   number as currently specified, the transport socket operation of DHCP
   packets would need to go through a central entity or process which
   would defeat the purpose of distributing DHCP relay functionality.

   In some large-scale deployment, the decision to split the DHCP
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