I am running tcpdump trying to track down a problem, and I am seeing something I have never seen before, there is a z before the protocol:

22:24:57.856983 x.x.x.x.1731 > some.fqdn.tld.z3950: S 2026246202:2026246202(0) win 64240 <mss 1460,nop,nop,sackOK>

Any idea what the z is?