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From: tcs@ccci.UUCP (Terry Slattery)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: When is a link saturated?
Message-ID: <9101301444.AA13881@ccci>
Date: 30 Jan 91 14:44:45 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The Internet
Lines: 27

This discussion on identifying port numbers for use with the cisco feature
of prioritizing packets for output has concentrated on the 'standard'
network utilities.  There are many applications other than telnet and ftp
that can benefit from this feature.  The developers of these applications
often need a way of getting the data through the network in a timely
manner.  When other users are running large FTP transfers, time critical
data may be delayed, reducing its value.  The cisco port priority feature
allows the net manager to specify certain traffic, by port number, as having
higher priority than other traffic.  Telnet vs ftp is generally not their
concern.  

For example, stock market data being sent from a ticker-plant to trader
workstations probably has higher priority than a background FTP of a
database dump between two systems.  Without the priority selection (or
type-of-service), the market data may be delayed enough to seriously affect
its value to the trader.

I'd also consider configuring routers to give priority to SNMP packets so
that if someone is choking the net, I can still perform net management
through the mess.  (Not as good as out-of-band control, but better than
nothing.)

	-tcs
Terry Slattery
Chesapeake Computer Consultants, Inc.		Network and Unix Consulting
2816 Southaven Drive				(301) 970-8076
Annapolis, MD  21401