"HOFMEISTER,JAMES (HP-USA,ex1)" wrote:

> RE: VT-MGR vs. Telnet
>
> Performance consideration with Telnet:
>
> 1) In our example 4 times more packets.
> 2) Each packet is a CPU interrupt on the HP-e3K system.
>
> I am 95% sure this is the way it works... but I will leave a 5% margin
> of error to give one of you diligent folks the incentive to take a TCP
> trace and do a packet by packet compare of the 2 protocols.

Close enough for government work <grin> but one other exception - If the
client side supports Nagle-style transmission deferral (see RFC896).
Unless you are a real slow hunt-and-peck typist, you will usually have
many of the input packets collapsed into fewer, longer packets.  An
excerpt from RFC896:

> The second case to examine is the same Telnet  test  but  over  a
> long-haul  link  with  a  5-second  round trip time.  Without any
> mechanism to prevent  small-packet  congestion,  25  new  packets
> would be sent in 5 seconds.* Overhead here is  4000%.   With  the
> classic timer scheme, and the same limit of 2 packets per second,
> there would still be 10 packets outstanding and  contributing  to
> congestion.  Round-trip time will not be improved by sending many
> packets, of course; in general it will be worse since the packets
> will  contend  for line time.  Overhead now drops to 1500%.  With
> our scheme, however, the first character from the user would find
> an  idle  TCP connection and would be sent immediately.  The next
> 24 characters, arriving from the user at 200ms  intervals,  would
> be  held  pending  a  message from the distant host.  When an ACK
> arrived for the first packet at the end of 5  seconds,  a  single
> packet  with  the 24 queued characters would be sent.  Our scheme
> thus results in an overhead reduction to 320% with no penalty  in
> response  time.

So, if you can type faster than your round trip time, it will reduce
the packet count by default if Nagle-type queueing is supported.

This applies only to standard telnet connections, however.  Connections
using "local-echo" (QCTerm's "advanced" telnet) already avoid the single
character packets.

Jeff

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