Re: [rrg] Next revision

[Robin Whittle <[e-mail]>]

Hi Tony,

You wrote:

>> I'll leave TTR and DFZ as an exercise for others.. :-)

OK, see below for DFZ.

I don't think "TTR" or "TTR mobility" needs to be defined in an
acronym list, since it is only used in the Ivip section, where it has
its own heading and explanation.  Here is a short definition if you
want to include it:

   TTR  Translating Tunnel Router, used for mobility, which plays
        the role of an ETR and to which mobile nodes connect via
        two-way tunnels from their one or more access network
        addresses.  TTRs also handle the mobile node's outgoing
        packets and so, typically, include an ITR function for those
        packets which need to be tunneled to ETRs.


Can you alter part of the Ivip summary?  Currently:

   Open ITRs in the DFZ (OITRDs, similar to LISP's PTRs) tunnel
   packets sent by hosts in networks which lack ITRs.

to:

   Default ITRs in the DFZ (DITRs, similar to LISP's Proxy Tunnel
   Routers) tunnel  packets sent by hosts in networks which
   lack ITRs.

This doesn't alter the substance of the summary, but brings it up to
date with my new terminology.


Here's a revision to the DFZ definition:


>    DFZ  Default-Free Zone: The collection of autonomous systems that do
>       not require a default route to forward a packet to any
>       destination.


     DFZ  Default-Free Zone: Routers in the interdomain routing
        system which have two or more "upstream" interfaces which
        carry best paths for all globally routed prefixes except
        those advertised by the router's own autonomous system.
        Routers with a single such "upstream" link assign the
        "default route" to this link, and so do not need to
        consider all the globally routed prefixes which originate
        in other autonomous systems.  Routers with two such upstream
        links cannot use any such "default route" because each such
        external prefix must be assigned to a specific one of the
        two or more upstream interfaces.  Routers with two or more
        upstream links are said to be in the Default-Free Zone of
        the interdomain routing system - and so must handle all the
        prefixes advertised in the interdomain routing system.


Sorry this is long, but "DFZ" is an important and obtuse term which
needs to be defined clearly.  I don't agree with the "collection of
autonomous systems" definition, which seems to be from the Wikipedia
page:

  http://en.wikipedia.org/wiki/DFZ

An AS can have many routers and only some of those routers are in the
DFZ, as best I understand it.

  - Robin