Subject: Re: [rrg] Next revision

From: [email-masked] (Noel Chiappa)
Date: Wed, 24 Feb 2010 17:39:41 -0500 (EST)

> From: Tony Li <[email-masked]>

    > Would folks care to contribute expansions, please?

ETR - Exit Tunnel Router: In a system which tunnels traffic across the
existing infrastructure by encapsulating it, the device close to the actual
ultimate destination which decapsulates the traffic before forwarding it to
that ultimate destination.

ITR - Ingress Tunnel Router: In a system which tunnels traffic across the
existing infrastructure by encapsulating it, the device close to the actual
original source which encapsulates the traffic before using the tunnel to
send it to the appropriate ETR.

xTR - Tunnel Router: In some systems, the term used to describe a device
which can function as both an ITR and an ETR.

PMTUD - Path Maximum Transmission Unit Detection: The process or mechanism
which determines the largest packet that can be sent between a given source
and destination with being either i) fragmented (IPv4 only), or ii) discarded
(if not fragmentable) because it is too large to be sent down one link in the
path from the source to the destination.

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

	Noel

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From: Tony Li <[email-masked]>
Date: Wed, 24 Feb 2010 17:54:05 -0800

Noel,

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

Thank you for your contribution.  I've included them and added a few.
Anyone else?

Tony

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

   EID  Endpoint IDentifer: The precise definition varies depending on
      the proposal.

   ETR  Egress Tunnel Router: In a system which tunnels traffic across
      the existing infrastructure by encapsulating it, the device close
      to the actual ultimate destination which decapsulates the traffic
      before forwarding it to that ultimate destination.

   FIB  Forwarding Information Base: The forwarding table, used in the
      data plane of routers to make forwarding decisions.

   ITR  Ingress Tunnel Router: In a system which tunnels traffic across
      the existing infrastructure by encapsulating it, the device close
      to the actual original source which encapsulates the traffic
      before using the tunnel to send it to the appropriate ETR.

   PA Provider Assigned: Address space assigned by the service provider.

   PI Provider Independent: Address space independent of any service
      provider.

   PMTUD  Path Maximum Transmission Unit Discovery: The process or
      mechanism that determines the largest packet that can be sent
      between a given source and destination with being either i)
      fragmented (IPv4 only), or ii) discarded (if not fragmentable)
      because it is too large to be sent down one link in the path from
      the source to the destination.

   RIB  Routing Information Base.  The routing table, used in the
      control plane of routers to exchange routing information and
      construct the FIB.

   RLOC  Routing LOCator: The precise definition varies dependeing on
      the proposal.

   xTR  Tunnel Router: In some systems, the term used to describe a
      device which can function as both an ITR and an ETR.

---

From: Robin Whittle <[email-masked]>
Date: Thu, 25 Feb 2010 15:56:39 +1100

Hi Tony,

>> 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.

>       not require a default route to forward a packet to any

     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

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From: Tony Li <[email-masked]>
Date: Thu, 25 Feb 2010 08:59:37 -0800

Hi Robin,

> its own heading and explanation.

Thank you, I concur.

>    Routers) tunnel  packets sent by hosts in networks which

Done.

> needs to be defined clearly.

Agreed, but brevity is a requirement.

> DFZ, as best I understand it.

Disagree.  In common usage, DFZ is an AS level concept.  Your definition is
precise about the technical requirements, but doesn't match the pragmatic
usage in the world.  Consider the case of a single-interface route reflector
in the middle of a very large, well connected ISP.  That particular router
COULD use default for its single interface, but its other duties certainly
require that it have full routing.

Tony