Generalized UDP Source Port for DHCP Relay
draft-ietf-dhc-relay-port-05

Document Type Active Internet-Draft (dhc WG)
Last updated 2017-04-28 (latest revision 2017-04-25)
Replaces draft-shen-dhc-client-port
Stream IETF
Intended RFC status Proposed Standard
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Document shepherd Tomek Mrugalski
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Send notices to "Tomek Mrugalski" <tomasz.mrugalski@gmail.com>
Networking Working Group                                         N. Shen
Internet-Draft                                                   E. Chen
Intended status: Standards Track                           Cisco Systems
Expires: October 27, 2017                                 April 25, 2017

               Generalized UDP Source Port for DHCP Relay
                      draft-ietf-dhc-relay-port-05

Abstract

   This document proposes an extension to the DHCP protocols that allows
   a relay agent to receive packets from a server or an upstream relay
   agent on any UDP port, not just the default port 67 for IPv4 or
   default port 547 for IPv6.

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 October 27, 2017.

Copyright Notice

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

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Shen & Chen             Expires October 27, 2017                [Page 1]
Internet-Draft           DHCP Relay Source Port               April 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
   6.  An IPv6 Cascaded Relay Example  . . . . . . . . . . . . . . .   7
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   8
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   9.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   8
   10. Normative References  . . . . . . . . . . . . . . . . . . . .   9
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   9

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).

   This fixed UDP port of 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
   functionality into multiple processes on a node may not be purely
   based on DHCP relay computational load.  But rather DHCP relay could
   just be one of the functions in a multi-process implementation.
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