Re: TCP Checksum Interoperability

[Matt Crawford <[e-mail]>]

> and RFC791 claims ttl is in seconds, ergo I don't have to decrement
> ttl because I know my traffic is on paths less than a second
> long.
> 
> Cool reasoning.

You lose -- 791 says you have to subtract at least 1 from TTL even if.

However, I think that (A) most or all extant IPv4 routers violate 791
if they happen hold a packet more than a second, and (B) IPv6
invalidated TCP's correctness by defining the Hop Limit field to be a
hop limit and have no connection to time.  A TCP riding on IPv6 may
receive old segments an unbounded time later without any other
network element breaking a spec.

I said so at the time, but nobody cared.  No doubt Vint will take
care of multi-second hops for us.