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Multicast/ Broadcast Mechanism for a Shared Buffer Packet Switch

IP.com Disclosure Number: IPCOM000107673D
Original Publication Date: 1992-Mar-01
Included in the Prior Art Database: 2005-Mar-22
Document File: 2 page(s) / 97K

Publishing Venue

IBM

Related People

Engbersen, JA: AUTHOR

Abstract

Disclosed is a mechanism to effectively implement multicast/broadcast in a shared output-buffer packet switch. Because the buffer is shared, use of the buffer requires only one copy of the multicast/broadcast packet to be kept.

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

Multicast/ Broadcast Mechanism for a Shared Buffer Packet Switch

       Disclosed is a mechanism to effectively implement
multicast/broadcast in a shared output-buffer packet switch. Because
the buffer is shared, use of the buffer requires only one copy of the
multicast/broadcast packet to be kept.

      In order to output one copy of a packet on more then one output
of the switch, it is sufficient to keep only one copy of the original
packet in the shared buffer until all copies have been transmitted on
all indicated outputs.  For that, three mechanisms are required in
addition to the basic shared output-buffer packet switch mechanism
described in (*).
1.   A mechanism to derive a mask from the header of the incoming
packet to determine which outputs will receive a copy of this packet.
2.   A mechanism to provide each control queue of the outputs
designated with a copy of the address where the multicast/ broadcast
packet resides in the shared output buffer.
3.   A mechanism to determine when the copy of the
multicast/broadcast packet in the shared output buffer is no longer
needed.

      The selection mechanism to connect a shared output buffer
location to a specific switch output is able to connect one shared
buffer location to multiple outputs at the same time.  This is clear
for those skilled in the art from the description in (*).

      The figure shows a block diagram of the total switch principle.
Only the shaded blocks, or parts of blocks, pertain to the multicast/
broadcast principle discussed here.  All other blocks and their
operation are explained in (*).
Operation

      Packets enter the switch through inputs 1 on the left. By
virtue of 'routers', every incoming packet is routed entirely to a
packet buffer location 2 exclusively reserved for this packet.  A
copy of the packet header byte, and the address of the packet buffer
location where this packet is routed to, are sent to the control
section in...