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Automatic Network Routing With Link-by-Link Recovery Disclosure Number: IPCOM000100471D
Original Publication Date: 1990-Apr-01
Included in the Prior Art Database: 2005-Mar-15
Document File: 3 page(s) / 121K

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Goldstein, BC: AUTHOR [+2]


This article describes an invention which permits link-by-link recovery while using the Automatic Network Routing (ANR) technique.

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Automatic Network Routing With Link-by-Link Recovery

       This article describes an invention which permits
link-by-link recovery while using the Automatic Network Routing (ANR)

      Automatic Network Routing is a technique used for routing
packets in high speed networks.  We briefly review the basic
technique used there.  The ANR field is composed of n words.  The ith
word in the ANR field defines the outgoing link label for the ith hop
along the packet path. The outgoing link label is essentially the
internal switch ID or address (SID) of the outgoing link adapter.
Thus, the packet header contains all the routing i formation
necessary for the routing of the packet within each intermediate node
along the path.  As the packet progresses through the network, the
"used" SIDs are stripped off, so that the first bits in the ANR field
always contain the routing information for the current node.  This
process is depicted in Fig. 1. Thus, every node will examine a fixed
location in the header without having to know of its position in the
path.  No external table look-ups or processing is necessary, thereby
ensuring minimal nodal delay.

      The major advantage of ANR is that it is possible to achieve
very high speeds by using dedicated high-speed routing hardware to
perform the routing with minimal processing overhead in the transport
path.  However, the necessity to avoid processing overhead prevents
the implementation of conventional link-by-link error recovery
schemes.  (The error recovery schemes are required because of packet
losses by random bit error on the links or due to buffer overflows
within the nodes).  Thus, end-to-end error recovery schemes are the
only mechanisms used to guarantee data integrity. For error prone
links, the performance of end-to-end schemes is significantly poorer
than link-by-link schemes.  This invention permits the implementation
of link-by-link error recovery while preserving the speed of ANR

      Automatic Network Routing with Link-by-Link Recovery We first
describe a previously known modification of the basic ANR technique -
the ANR-with-copy.  We assume that every node has, in addition to the
fast routing hardware, a processor that is used to execute network
control functions or more complex data transport protocols.  In the
ANR-with-copy mechanism a packet is routed as before to the
appropriate output link through the fast hardware and is copied in
parallel to a processor attached to the switching hardware.  This
copy function is indicated by a special bit(s) in the packet header.
Thus, it is possible for the processor in every intermediate node
along the path to receive a copy of the packe...