Browse Prior Art Database

Source Routing Bridge Modification to allow Unlimited Spanning Free Explorer Frame Hops

IP.com Disclosure Number: IPCOM000106700D
Original Publication Date: 1993-Dec-01
Included in the Prior Art Database: 2005-Mar-21
Document File: 2 page(s) / 38K

Publishing Venue

IBM

Related People

Sendelbach, LE: AUTHOR

Abstract

One of the inherent limitations of source-routing networks is the number of hops a frame can take through the network. A hop is defined as a traversal of a bridge in the network. The number of hops is limited by the size of the Routing Information (RI) field of the frame. Currently this field is limited to a maximum of 30 bytes of which 28 bytes can be used to hold the source routing path through the network. With a 30 byte RI field a maximum of 13 hops is allowed. With an 18 byte RI field a maximum of 7 hops is allowed.

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Source Routing Bridge Modification to allow Unlimited Spanning Free Explorer Frame Hops

      One of the inherent limitations of source-routing networks is
the number of hops a frame can take through the network.  A hop is
defined as a traversal of a bridge in the network.  The number of
hops is limited by the size of the Routing Information (RI) field of
the frame.  Currently this field is limited to a maximum of 30 bytes
of which 28 bytes can be used to hold the source routing path through
the network.  With a 30 byte RI field a maximum of 13 hops is
allowed.  With an 18 byte RI field a maximum of 7 hops is allowed.

      Disclosed is a modification for source-routing bridges which
can overcome these limitations for Spanning Tree Explorer (STE)
frames on a source routed networks.  STE frames follow the spanning
tree through a source-routed network similar to an Ethernet frame in
an Ethernet network.  While the STE frame is traversing the network,
each bridge updates the RI field with the current hop information.
When the maximum RI field length is reached the frame is discarded.
The modification for the source routing bridge is to only update the
last entry in the RI field continually for STE frames after the the
RI has reached the maximum number of hops allowed in the network.
STE frames which are re-received by the bridge after circulating
around the ring are discarded by the bridge using the information in
the last field of the RI.  This technique will...