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3 DQDB - DQDB Application: As A Backbone Network
Citation preview
1DQDB -
All rights reserved. No part of this publication and file may be reproduced, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior written permission of Professor Nen-Fu Huang (E-mail: [email protected]).
Distributed Queue Dual Bus(IEEE 802.6 DQDB)
2DQDB -
DQDB Network Structure
3DQDB -
DQDB Application: As A Backbone Network
4DQDB -
DQDB Based Metropolitan Area Networks
5DQDB -
DQDB Node Structure
6DQDB -
DQDB Access Structure (Or-Write Circuit)
7DQDB -
Looped Bus Structure of a DQDB Network
8DQDB -
Network Reconfiguration Examples
9DQDB -
Slot Structure (Fixed Length, 53 Octets)
Queued-Arbitraed (QA) Access Method
l Busy Bit l Request Bit
11DQDB -
Queued-Arbitrated (QA) Slot Access
When a node does not have a QA segment to send on Bus A
12DQDB -
Queued-Arbitrated (QA) Slot Access
When a node does have a QA segment to send on Bus A
13DQDB -
QA Access Operation Example
A sub-network consisting of five nodes queuing for access
RQ: Request Counter CD : Countdown Counter All slots passing on bus A are busy Nodes 5, 2, and 3 queue for access in that
order
14DQDB -
QA Access Operation Example
15DQDB -
QA Access Operation Example
16DQDB -
MAC Connectionless Service PDU
17DQDB -
Segmentation of an IMPDU into DMPDUs
18DQDB -
DMPDU to Slot
19DQDB -
MID Page Allocation Protocol
20DQDB -
MID Page Allocation Protocol
21DQDB -
Address Format
22DQDB -
Isochronous Channel Concepts andPA Slot Format
23DQDB -
Isochronous Channels Examples
24DQDB -
Isochronous Channels Examples
25DQDB -
Establishment of Isochronous Channels
26DQDB -
Layer Management Message Flows at the Originating Site
27DQDB -
Layer Management Message Flows at the Originating Site
28DQDB -
Layer Management Message Flows at the Originating Site
29DQDB -
DQDB Access Method Characteristics
Provides two modes of access: Non-Arbitrated Access (Pre-Arbitrated, PA) Queued-Arbitrated Access (QA)
PA access supports Isochronous connection-oriented services
QA access supports Asynchronous services QA access supports three priority levels QA access provides low access delays at low subnetwork
loading and little wasted capacity at high loading The relative throughput that can be supported by QA
access is independent of sub-network size or bit rate Operates as a network in a size of 50km (diameter) Slotted structure compatible with broadband-ISDN