[ih] Source routing, IEN 80, and IEN 95 (in use)

[Mike Brescia]

John,

You got it exactly right.  You cannot "stop and ask for directions" from normal routing when something may have broken it.

In the early days of SATNET (1978..), when the routing or the SATNET or ARPANET network infrastructure failed between the U.S. either the U.K. or Europe, fallback source routes configured in the monitoring and control program were used to get around the failure.  On ARPANET and SATNET, failure of one of the satellite links would isolate parts of one net and a set of configured source-routes via other nets would be tried as the way to reach nodes which were not normally responding, bypassing the break.  The only programs I saw using this approach was the IMP monitor/control program NU and before that, U.  Oh, and later, monitoring for the "Wideband" net also at BBN.

While a user tool (e.g. telnet, ftp) may have had a source-route command line option to force a bypass in extreme cases, I cannot recall those tools having a configuration file setup for trying fallback routes.

network example: (forgive the ASCII "art")

NOC ..2................>
 |       ARPANET(10)    .
 +-------+=========+-------+ 
  ..1..  |         |    .
      .  R1        R2   .
      .  |         |    .
      v  +         +    v
          \       /
  SATNET(4) XXXXX
          /       \
         +         +

NOC = network ops center
 +  = network node (IMP, SATNET IMP)
=== = ARPANET satellite link
 R  = gateway(router)
XXX = break in SATNET isolating parts of net 4
.1. = normal path to net 4 via R1
.2. = source-routed path to isolated part of net 4 via R2


 -- Mike Brescia (BBN &seq. '78-'02)


On Aug 5, 2010, at 7:10 PM, John Day wrote:
> Source routing is a male thing  -  the packets don't want to stop and ask for directions.
> 
> ;-)  Sorry, couldn't resist.
> 
> 
> At 0:40 +0200 2010/08/06, Matthias Bärwolff wrote:
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>> Hi everyone out there. I am wondering (mainly just out of curiosity)
>> about the implementation and usage record of source routing in the early
>> Internet. The IPv4 spec (starting with IEN 80) came to include it
>> eventually, but my impression is that while people *thought* it would be
>> important, in reality no one cared too much and it wasn't used much.
>> 
>> My question: have people actually been using it for purposes other than
>> spoofing attacks? What about routing debugging? And, load balancing?
>> 
>> Plus, how widespread did it become in gateways/routers before security
>> concerns rendered it a complete no-go?
>> 
>> Thanks for your recounts and takes.
>> 
>> - --
>> Matthias Bärwolff
>> www.bärwolff.de
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