Re: [RRG] Re: Ivip6: number of "Flow Label" bits required

[Robin Whittle <rw@firstpr.com.au>]

Hi Brian,

This is very cool.  I understand you are sitting in an airport
lounge in Japan, drawing from experience which goes waaay back:

>> Short version:   The Ivip6 (formerly FLOWv6) proposal won't
>>                  need the full 2^20 range of bits in the IPv6
>>                  Flow Label.  Each possible value is for a
>>                  BGP-advertised prefix for forwarding packets to
>>                  when they are addressed to the new kind of
>>                  end-user network.
> 
> OK, explained like that, it seems coherent with Pouzin's
> proposal in 1974 that the catenet address format should be
> 
> <Format> <PSN name> <Local name>
> 
> where you propose to put the <PSN name> in the current flow label
> field. 

Yes.

> Pouzin's full explanation read:
>
> "There is no need to interpret the destination address any more than
> required to find an appropriate gateway in the correct direction.
> Putting gateway names in addresses is unacceptable, as it would
> tie up addressing and network topology. Thus, only PSN [packet
> switched network] names should be used as catenet [internet]
> addresses. Delivering a message to a final destination is carried
> out only by the final PSN."
> 
> [Pouzin74] Pouzin, L., Interconnection of packet switching networks,
> 7th Hawaii International Conference on System Sciences, Supplement,
> pp. 108-109, 1974.

That's right.  I couldn't find the paper on the Net, so I guess you
have it on your laptop - maybe as part of your teaching materials.
Searching for the text turns up your message:

  http://psg.com/lists/rrg/2008/msg01384.html  2008-05-29

in which you wrote:

> Now, I fear he was right, but that's not what got implemented.
>
> We got a model based on fixed length addresses without a format
> prefix. I didn't see in the IPng discussion and don't see now how
> we can jettison that.

I think we can use use the 20 bits of "Flow Label" in the IPv6 for a
different purpose.  As you wrote in an earlier message, this would
be completely contrary to the intention that they not be used as a
"routing handle".	

This would be an adjunct to the current system, for the particular
purpose of getting packets from an ITR across the core to the
provider network where the destination network is located.  However,
if the system is successful, this would include the great majority
of traffic in the core.

This proposal uses the existing BGP network, with somewhat modified
routers, while doing less work in the FIB, and delivering the packet
to the the single border router for that prefix, or to one of the
several border routers which advertise it.

You also wrote:

  http://psg.com/lists/rrg/2008/msg01392.html

> Pouzin's catenet paper from 1974 clearly shows hosts
> multihomed to two different networks. He even had virtualized
> multihomed hosts in there. That paper is hard to find without
> going to a copyright library.

It looks like there is a copy here at Monash Uni Library.

Perhaps a similar paper is:

   Pouzin, L., "A Proposal for Interconnecting Packet Switching
   Networks," Proceedings of EUROCOMP, Brunel University, May 1974,
   pp. 1023-36.


I am looking for a term for using this Routing Label approach to
forwarding a packet across the core, since it is not a map-encap
"tunnel" and nor is it using "translation".  Maybe I can work Louis
Pouzin's name into the terminology.

  - Robin


--
to unsubscribe send a message to rrg-request@psg.com with the
word 'unsubscribe' in a single line as the message text body.
archive: <http://psg.com/lists/rrg/> & ftp://psg.com/pub/lists/rrg