On Thu, 18 May 1995, Bill Bunting wrote:
> Yes, I have seen the same thing with Windows For Workgroups if you specify
> TCP/IP as the default protocol. Some of the programs (like chat) also use
> TCP on these ports. If anyone knows exactly what is going on, I would be
> At 08:35 PM 5/17/95 -0700, Tim Keanini wrote:
> >I have solved a mystery on one of my internel networks.
> >I would like to share it with you all:
> >If you install the Windows 95 package, there are these broadcasted UDP
> >packets that are on src and dst port 137 and 138 UDP. From what I
> >have gathered, it is Windows 95 trying to tunnel NETBIOS via UDP.
> >Just wanted to share.
According to RFC 1001, UDP port 137 is the NetBIOS Name Service (NBDS)
and port 138 is the NetBIOS Datagram Distribution Serive (NBDD).
According to the RFC, services that use 138 can be very chatty, not only
over 138 (because it is a broadcast port), but on 137 as well. It seems
that every time a packet is sent out, NetBIOS has to look up the address
via NBDS. The impression I am getting is that each machine does not do
any cacheing of names and looks *everything* up.
I would suggest that anyone who has to deal with pee cees on a TCP/IP
network get a copy of RFC 1001 and 1002. They are very informative and
makes one appreciate Unix even more!!