Re: ICMP's & IP src addrs


tmallory@PARK-STREET.BBN.COM
Fri, 23 Sep 88 17:53:31 -0400


> Hhmmm, you mean your hosts receive a packet on their ethernets and
>don't record the mapping of source ethernet and IP addresses in their ARP
>caches? Doesn't sound like a very good idea to me. I'd say there's
>probably a pretty good chance you're going to have to send a packet back
>to any host you receive one from ...

While it this would help a lot with the traffic associated with the broadcast
pings, recording, or at least checking, the IP/hardware address mapping for
the source of every IP packet received seems wasteful, since it's purpose is
to save an infrequent ARP request. If I receive 10000 packets from the same
host, I'm not sure I want to check the logical/hardware mapping table every
single time. Also, there is the problem that the source address in the IP
header may well not match the source hardware address if the packet has been
sent through a gateway. OK, so you only insert the mapping if the network
number matches the attached network. But some hosts support multiple network
numbers for the same network, so the packet might still have come from a
gateway... This gets complicated, and the layering isn't very pretty. I
don't think many hosts do it, but I'd be happy to hear otherwise.

Tracy

PS: If a host wants to match IP source addresses with particular hardware
addresses for some limited flavor of security, then my main objection is moot.



This archive was generated by hypermail 2.0b3 on Thu Mar 09 2000 - 14:43:30 GMT