tcp counters


Mike Brescia (brescia@ccv.bbn.com)
25 Feb 87 14:50:19 EST (Wed)


For each type of host implementation of IP/TCP/TELNET, where may the tcp error
counters be found? I realize that some UNIX(tm) systems and derivatives
provide a netstat command with a '-s' option that gives the following counters
for the tcp level.

tcp:
        0 bad header checksums
        0 bad header offset fields
        0 incomplete headers

The information I am looking for is a measure (either per-connection or over
the whole operation of the tcp protocol layer)

 retransmissions - count of segments resent because ack was not returned in time
 redundant receives - count of segments received more than once
 estimated round trip time (per connection) - delay to destination
 retransmission time (or algorithm from est. RT time)
 route (on UNIX() can get this from netstat -r) - gateway or interface used
 when a connection is closed, the reason for closing

For your implementation, are these sort of numbers available to me, a lowly
user, and if not, can a wizard get them using some debugging magic?

Implementations ::= { tops20, 4.*bsd, bbnos, ultrix 1.*, 2.*, vms(wolongong),
                      many others? }

I have taken a call from a user who is unable to reliably get from host A to
host B, in that the connections hang for long periods of time, and frequently
break (connection closed). While there are 3 different kinds of gateway in
this particular path, I think the routing and traffic load are stable enough
to support useful ftp and telnet service. I want to be able to have her call
her host wizard to find out what is failing at the end points.

        mike



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