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Browse Prior Art Database

Information Broadcasting as Integral Part of a Protocol for LANs

IP.com Disclosure Number: IPCOM000110060D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 3 page(s) / 164K

Publishing Venue

IBM

Related People

Lemppenau, WW: AUTHOR [+2]

Abstract

A Medium Access Control (MAC) protocol for ring and bus LANs with a slotted transmission structure where slots are accessed through two distinct mechanisms: immediate access of so-called gratis slots and access of previously reserved slots is described in (*). A gratis/ reserved flag is used to distinguish between these two states of a slot. In both cases, the busy/free flag needs to be free for the slot to be accessible. Reserved slots are marked by a scheduler and their access is only for one transmission. Reservation requires a prior Reserve/Confirm command exchange with the scheduler.

This text was extracted from an ASCII text file.
This is the abbreviated version, containing approximately 51% of the total text.

Information Broadcasting as Integral Part of a Protocol for LANs

       A Medium Access Control (MAC) protocol for ring and bus
LANs with a slotted transmission structure where slots are accessed
through two distinct mechanisms: immediate access of so-called gratis
slots and access of previously reserved slots is described in (*).  A
gratis/ reserved flag is used to distinguish between these two states
of a slot.  In both cases, the busy/free flag needs to be free for
the slot to be accessible.  Reserved slots are marked by a scheduler
and their access is only for one transmission.  Reservation requires
a prior Reserve/Confirm command exchange with the scheduler.

      Fig. 1 illustrates six instants of this command exchange for a
ring with N active nodes: (1) the scheduler issues a Reserve command
consisting of two back-to-back delimiters (Start and End); (2) nodes
participating in the reservation process, insert a request entry into
the passing Reserve command; when the Reserve command arrives at node
k, its length has been increased by k-1 entries; (3) upon return of
the Reserve command, the scheduler processes all N entries to
allocate slot reservations fairly; (4) subsequently, it issues a
Confirm command consisting of a confirm entry for each of the N
reserving nodes; (5) as nodes successively remove their entry, the
command length shrinks gradually; when the Confirm command visits
node k, it contains the remaining entries k through N; (6) the
Confirm command ultimately returns to the scheduler consisting of
only the back-to-back Start/End delimiters.

      The insert/remove command transmission technique, which is
tailored for multi-gigabit/s speeds, requires that scheduler and
nodes temporarily increase the network length by inserting a delay
register.  Its size corresponds to that of the inserted entry.  This
technique permits to exchange node-specific information between nodes
and scheduler without explicit addresses by specifying the rule that
an entry insertion occurs before the End delimiter and a removal
after the Start delimiter.

      With a minimum of extra transmission overhead, this reservation
scheme can be extended to broadcast additional information.  It can
be used separately, too.  The cyclic broadcast may be related to
always the same kind of information or different kinds (but
sequentially in some order), and may be continuously or on-demand.
One important application is for network management.  An example is
address-label broadcasting of all nodes that take part in the
reservation procedure so that the scheduler can associate
transmission activities with node addresses.  Another application is
for minimum hop routing in a dual- ring network.  Here, a node
transmits on the ring with the minimum number of active nodes on its
path to its destination.

      Fig. 2 illustrates the integ...