Routing without source information and Traffic self-similarity

Nathan Boyd boydn at
Thu Sep 18 21:03:26 UTC 1997

> Okay... I'll bite... 

Thanks! ;>

> Maybe I am just naive but if the IP header did not contain a source
> address, how would TCP acknowledgement, windowing, or re-transmission take
> place?
> How would a request for data be serviced?  Would responses always be in
> the form of a all-nets/all-hosts broadcast?  How else would the response
> get back to the originating host?

The point is that the source address is not explicitly *required* in the
*header*.  Thus, a source and destination could "setup" an IP session by
negotiating a "session ID" or something - the first packet from source to
destination would include the source's address in the *payload* along with
information to start the negotiation process.  I am describing, in other words,
something like an ATM transport layer that would live below IP.

> [snip]
> Routing Protocols.... we need source addressing so we know, at the IP
> layer, who our sources of information are, and then, who can we accept
> information from and who we should refuse information from.  In addition,
> access-lists, route-filters, and other types of security would be
> non-functional without source addresses.

Now you're addressing (so to speak ;) the kind of issues that I am concerned
with: without mandating source information in the header, how can the
destination make decisions about rejecting/accepting traffic? alternatively,
how can middle agents (e.g., routers) do filtering, etc.? how can we
possibly prevent spoofing?

> Lastly, how would you accomplish a traceroute on a network with no source
> addressing?  Where would the ICMP ttl expired messages be directed if
> there was no source address in the packet?

I don't know!  You tell me!  Do we make each intermediate router "aware" of
the negotiated session ID?  Doesn't sound tractable to me.

I hope this clarifies this - I don't think it is so strivial as my initial
email led you to believe.



More information about the NANOG mailing list