Browse Prior Art Database

Isochronous Transmission on a Token Ring LAN

IP.com Disclosure Number: IPCOM000105300D
Original Publication Date: 1993-Jul-01
Included in the Prior Art Database: 2005-Mar-19
Document File: 4 page(s) / 140K

Publishing Venue

IBM

Related People

Herzberg, LP: AUTHOR [+2]

Abstract

This invention provides a means to achieve isochronous capability on a upgraded standard Token Ring (TR) installation. It enables the intermixed usage of both standard non-isochronous stations (NIS) and newly defined (to be developed) isochronous stations (IS). It makes use of the cabling in place to allow both standard TR non-real-time (NRT) token based operation and a new real-time-isochronous (RTI) operation.

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Isochronous Transmission on a Token Ring LAN

      This invention provides a means to achieve isochronous
capability on a upgraded standard Token Ring (TR) installation.  It
enables the intermixed usage of both standard non-isochronous
stations (

NIS

) and newly defined (to be developed) isochronous
stations (IS).  It makes use of the cabling in place to allow both
standard TR non-real-time (NRT) token based operation and a new
real-time-isochronous (RTI) operation.

      The RTI operation supplies guaranteed fixed bandwidth at
constant end-to-end delay required by isochronous transmission.  The
NRT and RTI are temporally alternating transmissions on standard TR
media, operating as described herein.  RTI transmissions occur in
controller allotted time segments every 125us.  NRT transmissions
occur for the remaining ring time as shown in Fig. 1(a).  Station
segment forwarding is as shown Fig. 2.

      The elements of this invention are the means to provide the
following features:

1.  It enables full isochronous performance to a LAN heretofore not
    capable of real-time guaranteed bandwidth allocation.
2.  It makes use of the cabling installation in place.
3.  It allows the continued usage of heretofore standard stations in
    the same TR with new isochronous capable stations.
4.  The isochronous operation is quasi-transparent to the
    non-isochronous stations in a specification conforming manner.
5.  It invents a means to perform the functions required for full
    isochronous communications in a separate entity such as to enable
    the sharing of the Token Ring assets by both heretofore standard
    TR stations (or MAUs) and new isochronous capable stations (or
    IMAUs, Isochronous MAUs).

     The means is achieved via the insertion of a herein described
Isochronous Module (IM) at each main ring input/output feed (MAU
etc).   Isochronous transmission on the ring is from IM to IM.  Each
IM forwards the isochronous time sector data to its upstream IM.
Each IM is capable or recognizing, synchronizing, receiving,
transmitting and repeating both RTI and NRT traffic.

      The RTI and NRT traffic are assigned time multiplexed ring
bandwidth by an Isochronous Master Station (IMS) as shown in Fig. 1.
The IMS assigns cells (portions) of the RTI bandwidth to satisfy
requests for real-time guaranteed bandwidth from isochronous
connections.  IMS control, RTI cell assignment and IM isochronous
transmit/receive synchronized operation can be according to any
defined protocol (such as FDDI-II) already known to those familiar
with the art, or by a newly to-be-defined TOKEN RING isochronous
protocol.

      MAU (and station) connections are recognized as being either
(IS) isochronous supporting stations or (NIS) non-isochronous
supporting stations (old-standard stations).  The IM forwards all
traffic, both NRT and RTI, to the IS.  It forwards only NRT traffic
to the NIS.  Each IM maintain...