[e2e] Port numbers in the network layer?

Noel Chiappa jnc at mercury.lcs.mit.edu
Wed May 8 11:52:37 PDT 2013

    > At 7:53 AM -0400 5/3/13, dpreed at reed.com wrote:

    > (especially due to the much later decision to conflate
    > endpoint-identifier with route that got made by default at BBN, perhaps
    > just to get the thing bootstrapped)

I see that differently...

The thing is that path selection, to scale, just has to have a namespace in
which things can be aggregated. (You just can't give everyone a complete map
of every last physical asset in the entire network.) IP _only had one
namespace available_. So, yeah, as the network grew it had to be organized in
a way that was aggregatable.

That started to happen early on, with subnets, although it didn't come into
full flower until later, with CIDR. Yes, the very early network did have
addresses that (at the 'network' level) were flat - but even then, hosts were
not free to move from network to network and keep their 'identity' - because
internet-wide path selection didn't (couldn't?) track individual hosts.

It was inevitable that that aggregation would ensue as the network got larger
- as a direct, and unavoidable consequence of the fact that IPv4 had only one

A number of related issues were pointed out by Jerry in the paper that
eventually became RFC-1498, and those too pointed the same way: not enough


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