RFC 1046 (rfc1046) - Page 3 of 11

Queuing algorithm to provide type-of-service for IP links

RFC 1046                Type-of-Service Queuing            February 1988


Applications for Class of Service

   The following are examples of how classes of service might be used.
   They do not necessarily represent the best choices, but are presented
   only to illustrate how the different classes of service might be used
   to advantage.

   Interactive timesharing access using a line-at-a-time or character-
   at-a-time terminal (TTY) type of access is typically low volume
   typing speed input with low or high volume output.  Some Internet
   applications use echoplex or character by character echoing of user
   input by the destination host.  PC devices also have local files that
   may be uploaded to remote hosts in a streaming mode.  Supporting such
   traffic can require several types of service.  User keyboard input
   should be forwarded with low delay.  If echoplex is used, all user
   characters sent and echoed should be low delay to minimize the
   echoing delay.  The computer responses should be regular or high
   throughput depending upon the volume of data sent and the speed of
   the output device.  If the computer response is a single datagram of
   data, the user should get low delay for the response, to minimize the
   human/computer interaction time.  If however the output takes a while
   to read and digest, low delay computer responses are a waste of
   Internet resources.  When streaming input is being sent the data
   should be sent requesting high throughput or regular class of
   service.

   The IBM 3270 class of terminals typically have traffic volumes
   greater than TTY access.  Echoplex is not needed.  The output devices
   usually handle higher speed output streams and most sites do not have
   the ability to stream input.  Input is typically a screen at a time,
   but some PC implementations of 3270 use a variation of the protocol
   to effectively stream in volumes of data.  Low delay for low volume
   input and output is appropriate.  High throughput is appropriate for
   the higher volume traffic.

   Applications that transfer high volumes of data are typically
   streaming in one direction only, with acks for the data, on the
   return path.  The data transfer should be high throughput and the
   acks should probably be regular class of service.  Transfer
   initiation and termination might be served best with low delay class
   of service.

   Requests to, and responses from a time service might use low delay
   class of service effectively.

   These suggestions for class of service usage implies that the
   application sets the service based on the knowledge it has during the
   session.  Thus, the application should have control of this setting



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