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Priority Marking of Reserved Slots in a Reservation Based MAC-Protocol

IP.com Disclosure Number: IPCOM000110117D
Original Publication Date: 1992-Oct-01
Included in the Prior Art Database: 2005-Mar-25
Document File: 2 page(s) / 90K

Publishing Venue

IBM

Related People

Lemppenau, WW: AUTHOR [+2]

Abstract

Consider a ring or bus network with a slotted transmission structure where nodes access so-called gratis slots by a simple busy/free decision and reserved slots by a cyclic reservation procedure. A gratis/ reserved flag and a busy/free flag are used to distinguish between the four slot states. Reservation is done by a Reserve/Confirm command exchange in which cyclically transmission requests are collected, requests are processed by a scheduling node, and confirmations are returned to the requesting nodes. Marking of slots as reserved is done by the scheduler whereby a reservation is for only one transmission access. When a slot is freed by the destination, subsequent access to that slot is made via gratis access until the next marking takes place. Such a Media Access Control (MAC) protocol is described in (*).

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

Priority Marking of Reserved Slots in a Reservation Based MAC-Protocol

       Consider a ring or bus network with a slotted
transmission structure where nodes access so-called gratis slots by a
simple busy/free decision and reserved slots by a cyclic reservation
procedure.  A gratis/ reserved flag and a busy/free flag are used to
distinguish between the four slot states.  Reservation is done by a
Reserve/Confirm command exchange in which cyclically transmission
requests are collected, requests are processed by a scheduling node,
and confirmations are returned to the requesting nodes.  Marking of
slots as reserved is done by the scheduler whereby  a reservation is
for only one transmission access.  When a slot is freed  by the
destination, subsequent access to that slot is made via gratis access
until the next marking takes place.  Such a Media Access Control
(MAC) protocol is described in (*).

      Support of multiple priorities consists of replicating the
Reserve/Command handshake for each priority level and marking the
slots correspondingly.  Owing to slot re-use, lower priority
transmissions may occur before all transmissions of the highest
priority are done.  Here, a method is described which guarantees that
priority transmissions remain in strict priority order.  The main
idea is to borrow free-gratis slots when they become free at
destinations and to convert subsequently an equal number of reserved
slots back into gratis ones.  These reserved slots originate from the
marking process at the scheduler or they were borrowed in the same
way at upstream nodes.

      The figure illustrates the reservation and priority-marking
procedure for a priority cycle, whereby, for simplicity, the priority
attribute for commands, counters, and slot markings is omitted.  The
scheduling node S issues an empty Reserve command in which each of
the three nodes x, y, and z inserts its priority requests. ...