Modification to Default Value of SOL_MAX_RT

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Document Type Active Internet-Draft (dhc WG)
Last updated 2012-12-13
Replaces draft-droms-dhc-dhcpv6-solmaxrt-update
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Network Working Group                                           R. Droms
Internet-Draft                                             Cisco Systems
Updates: 3315 (if approved)                            December 13, 2012
Intended status: Standards Track
Expires: June 16, 2013

              Modification to Default Value of SOL_MAX_RT


   This document updates RFC 3315 by redefining the default value for
   SOL_MAX_RT and defining an option through which a DHCPv6 server can
   override the client's default value for SOL_MAX_RT with a new value.

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Droms                     Expires June 16, 2013                 [Page 1]
Internet-Draft          DHCPv6 SOL_MAX_RT Option           December 2012

1.  Introduction

   Section 5.5 of the DHCPv6 specification [RFC3315] defines the default
   value of SOL_MAX_RT to be 120 seconds.  In some circumstances, this
   default will lead to an unacceptably high volume of aggregated
   traffic at a DHCPv6 server.

   The change to SOL_MAX_RT is in response to DHCPv6 message rates
   observed at a DHCPv6 server in a deployment in which many DHCPv6
   clients are sending Solicit messages but the DHCPv6 server has been
   configured not to respond to those Solicit messages.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   document are to be interpreted as described in RFC 2119 [RFC2119].

2.  Update to RFC 3315

   This document changes section 5.5 of RFC 3315 [RFC3315] as follows:

      SOL_MAX_RT      120 secs  Max Solicit timeout value

      SOL_MAX_RT     3600 secs  Max Solicit timeout value

   With this change, a DHCPv6 client that does not receive a
   satisfactory response will send Solicit messages with the same
   initial frequency and exponential backoff as specified in section
   17.1.2 of RFC 3315 [RFC3315].  However, the long term behavior of
   these DHCPv6 clients will be to send a Solicit message every 3600
   seconds rather than every 120 seconds, significantly reducing the
   aggregated traffic at the DHCPv6 server.

3.  SOL_MAX_RT option

   A DHCPv6 server sends the SOL_MAX_RT option to a client to override
   the default value of SOL_MAX_RT.  The value of SOL_MAX_RT in the
   option replaces the default value defined in RFC 3315 [RFC3315].  One
   use for the SOL_MAX_RT option is to set a longer value for
   SOL_MAX_RT, which reduces the Solicit traffic from a client that has
   not received a response to its Solicit messages.

   The format of the SOL_MAX_RT option is:

Droms                     Expires June 16, 2013                 [Page 2]
Internet-Draft          DHCPv6 SOL_MAX_RT Option           December 2012

       0                   1                   2                   3
       0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
      |          option-code          |         option-len            |
      |                       SOL_MAX_RT value                        |

        option-code          OPTION_SOL_MAX_RT (TBD).

        option-len           4.

        SOL_MAX_RT value     Overriding value for SOL_MAX_RT in seconds.

                                 Figure 1

   A DHCPv6 client MUST include the SOL_MAX_RT option code in an Option
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