Casual technical question about /etc/services

Bennett Todd bet at
Tue Mar 23 19:00:35 PST 2004

2004-03-24T02:48:56 Joshua Brindle:
> You may be right in most cases but consider DNS

Yup, that's a terrific example, the best. Unless you've got some
faint control over the zone data, so you can avoid committing the
offense of to-huge rrsets in answer to possible queries, you've
gotta allow for the possibility of tcp. Me, I only use udp for
authoritative nameservers, never offer tcp, and only offer tcp when
I'm publishing for zone xfer, not UDP for that. But most folks don't
have the zone data control to safely do the former, and the zone
xfer client control to safely do the latter.

Perhaps ONCRPC (AKA sunrpc) is another juicy example? I don't have
anything running ONCRPC where I can get at it, but I thought recent
versions introduced an -over-tcp varient, which is used by newer NFS
versions to squeeze the speed out of gigabit ether.

There are probably a few more examples where both sides are
legitimately used, but the three telnet varients I see in my
/etc/services, four ftp varients, ssh, smtp, and basically almost
all the other services except for DNS, perhaps ONCRPC, and the
little idiot protocols embedded in inetd (echo, chargen, daytime,
etc.) mostly only use one or the other; /etc/services is almost
twice as long as it should be.

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