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Stream Transmission Protocol Implementation for CSMA/CD

IP.com Disclosure Number: IPCOM000108982D
Original Publication Date: 1992-Jul-01
Included in the Prior Art Database: 2005-Mar-23
Document File: 4 page(s) / 139K

Publishing Venue

IBM

Related People

Udupa, DK: AUTHOR

Abstract

Under heavy loads due to increased collisions, performance of Carrier-Sense Multiple Access with Collision Detection (CSMA/CD) protocol deteriorates. To overcome this limitation, four new frames are introduced.

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

Stream Transmission Protocol Implementation for CSMA/CD

       Under heavy loads due to increased collisions,
performance of Carrier-Sense Multiple Access with Collision Detection
(CSMA/CD) protocol deteriorates.  To overcome this limitation, four
new frames are introduced.

      For CSMA/CD, IEEE 802.2 and IEEE 802.3 frame formats are given
in Fig. 1.  CSMA/CD performs well when the traffic pattern is bursty
like in interactive applications.  In such an environment, the
traffic is not much and the collisions do not pose a major problem.
But, CSMA/CD does not perform well when the data traffic is stream.
Stream traffic is characterized by lengthy and continuous
transmissions.

      For this implementation, the following modifications for
CSMA/CD protocols are required.  The modifications are mainly
required in DA field of MAC.  The I/G bit of DA field is set to
1 to indicate that it is broadcast.
 .   The DSAP field of LLC frame is set to 'FF'.  This indicates that
the frames formed are for stream traffic.  In DA field of MAC, 6
bytes are used.
 .   The first frame is Start_Stream.req.  DA field is as shown in
Fig. 2.  There are no changes in other fields. It is assumed that the
bit numbered L is transmitted first and the bit numbered H is
transmitted last.  In the DA field, all bits have 1s except for the
last two bits.  The last two bits have 0s in the DA field.  This
frame is used by a station to seek permission to start transmission
for a set period of time.  Once a permission is given, no other
station can transmit. From this time on, the data transmission is
done in the normal manner.  This implies that the special frames
mentioned here are not required.
 .   The estimate of the time required for transmission can be put in
the Data field of Start_Stream.req.  The alternative method is to set
a maximum time limit for all the stations.  Either method will work
and is implementation dependent.
 .   When this Start_Stream.req is broadcast to all the stations, any
station can send a Reject_Stream.conf, if it wants to transmit.  DA
field of Reject_Stream.conf frame is shown in Fig. 5.  Otherwise, a
station will not reply.  When the Start_Stream.req is transmitted, a
timer is started.  If no Reject_Stream.conf frame is received within
the expiry of timer, all the stations agree that continuous
transmission by one station can be done.  The timer should be set
depending upon the transmission time to receive acknowledgement.
 .   The Reject_Stream.conf for the Start_Stream.req frame received
has to be a unique one, with all the bits except for the last bit
in the DA field set to zeros. The last bit is set to 1.  As
already mentioned, the I/G bit is set to 1.
 .   The other fr...