Generalize Client UDP Port Number of DHCP Relay
draft-shen-dhc-client-port-00

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Last updated 2016-06-20
Replaced by rfc8357, draft-ietf-dhc-relay-port
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Networking Working Group                                         N. Shen
Internet-Draft                                                   E. Chen
Intended status: Standards Track                           Cisco Systems
Expires: December 22, 2016                                 June 20, 2016

            Generalize Client UDP Port Number of DHCP Relay
                     draft-shen-dhc-client-port-00

Abstract

   This document extends the DHCP and DHCPv6 protocols for the UDP
   transport from server to client and allows the port to be any valid
   number on the DHCP relay system.

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 December 22, 2016.

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   Copyright (c) 2016 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Changes to DHCP and DHCPv6 Specifications . . . . . . . . . .   3
     2.1.  Changes to DHCP in RFC 2131 . . . . . . . . . . . . . . .   3
     2.2.  Changes to DHCPv6 in RFC 3315 . . . . . . . . . . . . . .   3
   3.  Compatibility . . . . . . . . . . . . . . . . . . . . . . . .   4
   4.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   4
   5.  Security Considerations . . . . . . . . . . . . . . . . . . .   4
   6.  Acknowledgments . . . . . . . . . . . . . . . . . . . . . . .   4
   7.  Document Change Log . . . . . . . . . . . . . . . . . . . . .   4
   8.  Normative References  . . . . . . . . . . . . . . . . . . . .   4
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   5

1.  Introduction

   RFC 2131 [RFC2131] and RFC 3315 [RFC3315] specify the DHCP transport
   protocol as UDP.  They also define both the server side and client
   side port numbers.  The DHCP server port is UDP number (67) and the
   client port is UDP number (68); for DHCPv6 the server port is (546)
   and the client port is (547).

   This client and server port definition is unusual in the normal
   Internet client/server protocols, as most of the protocols only have
   the server transport port number definition and leave the client port
   range to vary.  The main reason for the fixed DHCP client port number
   is due to the fact that the client may not have an IP address, so the
   client needs to listen on the well-known port for the DHCP server
   reply messages.

   Some implementations, including some open source DHCP
   implementations, do not allow this client port behavior to be changed
   by user configuration.  Some implementations allow the port number to
   be changed, but the client port is always the next number to the
   server port.

   This fixed client port number of DHCP protocol scheme creates
   problems in certain DHCP relay environments.  For instance, in a
   large scale DHCP relay implementation on a single switch node, the
   DHCP relay functionality may be distributed among multiple processes
   running under different CPUs.  All those DHCP relay processes share
   the same IP address of the switch node.  If the UDP source port has
   to be a fixed number, the transport socket operation of DHCP packets
   needs to go through a central location or process which defeats the
   purpose of distributed DHCP relay functionality.

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   This document proposes to relax the fixed client port requirement for
   the DHCP client or relay.  This extension requires the DHCP server or
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