Re: CU-Seeme problems
Thu, 9 Feb 1995 20:01:17 -0500

> The most recent version of the reflector software does not work with
> your set-up. The reason is that when SLIP sends a UDP packet, the
> packet contains the address of your SLIP client. The reflector,
> instead of reading this address from your packet, does a DNS lookup for
> your IP address (which of course is different since you are using SLIP
> and have essentially circumvented the normal domain name service.)
> Thus, the packets are probably arriving at the reflector, but the
> return packets from the reflector are going to a bogus address.

For the record, this is not exactly correct. To quote from a posting of
several days ago:

Each CU-SeeMe packet contains the (apparent) IP address of the machine on
which it originated (CU-SeeMe trying to find its own IP address is the
source of the dreaded "GetHost" error that Windows folks experience). This
is not intended to be used for network addressing, but just as a unique ID,
e.g., to identify which window a video packet belongs to. Currently, the
reflector software compares this supposed IP address with the actual source
IP address (from the IP header) and rejects the packet if they don't match.
I'm not sure why it does that; I think it was a quick fix to some problem
we observed. In any case, anyone who is in a situation where the IP
address that your machine thinks it has is different from the actual IP
source of the packet that reaches the reflector will not be able to connect
to a reflector.

It doesn't have anything to do with DNS, but with packets arriving from an
IP address that is different from the IP address where they originated
(where the "originating IP" is whatever the TCP/IP stack tells CU-SeeMe).
At least I'm pretty sure that's what's going on.

Tim Dorcey
Sr. Programmer/Analyst (607) 255-5715
Advanced Technologies & Planning
CIT Network Resources
Cornell University
Ithaca, NY 14850