Browse Prior Art Database

Priority Scheme for Token Ring in an ISDN Environment

IP.com Disclosure Number: IPCOM000099523D
Original Publication Date: 1990-Jan-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 99K

Publishing Venue

IBM

Related People

Bunkofske, RC: AUTHOR [+6]

Abstract

The modifications required for token ring frames in an ISDN environment are disclosed. The protocols for handling priorities are also disclosed.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 52% of the total text.

Priority Scheme for Token Ring in an ISDN Environment

       The modifications required for token ring frames in an
ISDN environment are disclosed.  The protocols for handling
priorities are also disclosed.

      The table in Fig. 1 shows the services required in the future
for an ISDN environment.  Most of these services will have to be
handled by LAN as well.  Those assigned higher priorities will be
transmitted before those of a lesser priority.

      As per the IEEE 802.5, token frame is as shown in Fig. 2.  An
improved priority scheme using a poll token format, as shown in Fig.
3, is being proposed.  To use this poll token, the priority algorithm
has to be changed.  The data frame formats will not change.

      For a poll token, all the AC bits are set to zero.  In the
ED field of a poll token frame, a poll token bit is set to indicate
that it is a poll token frame.

      In this scheme, there are two considerations for assigning data
transmission to a station.

      1.   Priority:  A station with the highest priority will
receive control to transmit data.

      2.   Time:  When stations have the same priority, the station
which has data requiring the shortest transmission time will receive
control first to transmit its data.

      Initially, the monitor puts in the highest priority and the
maximum time allowed for transmission.  As the poll token is
circulating around the ring, any station which has data to transmit
will look at the priority of the token and the time required.  A
station will seize this token if data to be transmitted is of a
higher priority.  When priorities are the same, a station will also
seize the token if the time required is less.  The new values are put
into the poll token by the station along with the station number.

      After the poll token goes once around the ring, the station
which has requested the poll token would seize the token and transmit
its data.
    In AC field, the p and r bits are set to zeros.
    However, if the timer expires during transmission, the poll token
should be circulated to poll all the stations. The...