[ih] internet-history Digest, Vol 15, Issue 3

[Bob Braden]

  *> I'm wondering if some of the sages on this mailing list might be able
  *> to shed some light on the origins of the term "router", in particular
  *> why it was introduced as a term distinct from "(packet) switch" or
  *> "gateway"?
  *> 

Packet switch is easy.  The first link layer (layer 2) for the Internet
was the ARPAnet, which was built of packet switches.  Did not want to
overload that term.

In the early days, we called them gateways (as in the very first
routing protocol, GGP -- Gateway-Gateway Protocol).

I don't recall who first started calling IP gateways "routers".  But
again, "gateway" rapidly became overloaded; the early ARPAnet/Milnet
lashup had email gateways.  And "router" clearly expressed the
essential semantics of packet forwarding in the IP layer.  So it was
probably natural for the "router" term to take over.

.
  *> The earliest reference to "router" that I can find in RFCs is in
  *> RFC753 from March 1979, which discusses message (email) routers,
  *> e.g. "The Router is responsible for maintaining sufficient topological
  *> information to determine where to forward any incoming Message-Bag."
  *> Such "application-level" routing is mentioned in several subsequent
  *> RFCs.
  *> 
  *> The first reference to routers in the context of the "network layer"
  *> appears in the April 1984 "Gateway SIG Meeting Notes" (RFC 898) in
  *> which Jon Postel mentions "leaving the normal router kernel function
  *> in charge of forwarding datagrams." and provides some history of "The
  *> CMU Gateway" which ?became? a "router" in "Oct 83".  RFC 1001 also
  *> mentions network layer routers, while RFC 1009 from June 1987 seems to
  *> be the first to define and discuss technical details of such routers:
  *> 
  *> "A router is a switch that receives data transmission units from input
  *> interfaces and, depending on the addresses in those units, routes them
  *> to the appropriate output interfaces."  "Interface Message Processors
  *> (IMPs) are packet-level routers."  "a gateway is an IP-level router"
  *> 

Yes, well, I believe that I wrote those words.  Still trying to get the
semantic space cleanly defined.

  *> 
  *> Is there, perhaps, a relationship between the use of the term "router" 
  *> and activity of that juggernaut of routers, Cisco? E.g. the first RFC to
  *> mention Cisco is RFC985 from May 1986.
  *> 

I don't recall that Cisco played a part here, but then Cisco was just
a tiny startup in those days...

Bob Braden

  *> 
  *> Tim Moors
  *> http://www.ee.unsw.edu.au/~timm/
  *> University of New South Wales
  *> Sydney, NSW, Australia
  *>  
  *> 
  *> 
  *> 
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  *> End of internet-history Digest, Vol 15, Issue 3
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  *>