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1 IEEE 8. LLC Logical Link Control ll 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 ( nfhuang@cs.nthu.edu.tw). LLC Specifications vinterface between LLC and Network Layer vinterface between LLC and MC Sublayer vprotocols between LLCs Sequence of message exchanges that take place between the LLC sublayers in the two stations in transferring data and control information from one station to another. Page

2 LLC Specifications LLC MC LLC MC Service ccess Point (SP) vllc provides Service ccess Point (SP) for higher layer protocols to access the services and multiplexing. v Connection is established between SSP (Source SP) and DSP (Destination SP). Page

3 Service ccess Point (SP) SP Service ccess Point (SP) IP IPX CLNS SPs Page

4 LLC Services vllc provides four types of services to the Network layer Type : Connectionless Service (Unreliable) u Datagram based Type : Connection-Oriented Service (Reliable) u Frame loss problem u Frame duplication problem u Frames out of order problem Type : Connectionless Service with ck (Reliable) u Datagram based Type : ll the above services LLC Services vfour kinds of Primitives Request ( ) Indication ( ) Response ( ) Confirm ( ) 8 Page

5 Using of Primitives SSP LLC LLC DSP 9 Primitives vtype DL-Unitdata.request DL-Unitdata.indication vtype Connection Establishment u DL-Connection.request u DL-Connection.indication u DL-Connection.response u DL-Connection.confirm Data Transfer u u u u DL-Data.request DL-Data.indication DL-Data.response DL-Data.confirm Page

6 Primitives (Type ) Connection Termination u DL-Disconnect.request u DL-Disconnect.indication Connection Resetting u DL-Reset.request u DL-Reset.indication u DL-Reset.response u DL-Reset.confirm Connection Flow Control u DL-Connection-Flowcontrol.request u DL-Connection-Flowcontrol.indication Primitives vtype DL-Data-ck.request DL-Data-ck.indication DL-Data-ck-Status.indication DL-Reply.request DL-Reply.indication DL-Reply-Status.indication DL-Reply-Update.request DL-Reply--Update-Status.indication Page

7 LLC Protocols vllc PDU (Protocol Data Unit) vthree kinds of Commands: Unnumbered Commands (U-format) Information Transfer Commands (I-format) Supervisory Commands (S-format) or - n DSP SSP DSP: Destination Service ccess Point SSP: Source Service ccess Point Unnumbered Command DSP SSP P/F Unnumbered Information (UI) P/F Exchange Identification (XID) P/F Test (TEST) P/F Set synchronous alanced Mode Extended (SME) P/F Unnumbered cknowledgement (U) P/F Disconnected Mode (DM) P/F Disconnect (DISC) P/F Frame Reject (FRMR) Page

8 Information Transfer Command DSP SSP Send Count - N(S) P/F Receive Count - N(R) 8 9 Sequence Number Send count N(S): The sequence number of this PDU Receive count N(R): The sequence number the LLC sublayer entity expects to find in the next LLC-PDU it receives. Supervisory Commands DSP SSP P/F Receive Count - N(R) Receive Ready (RR) P/F Receive Count - N(R) Reject (REJ) P/F Receive Count - N(R) Receive Not Ready (RNR) 8 9 Receive Ready (RR) Receive Not Ready (RNR) Reject (REJ) Page 8

9 Type Services Protocol Unnumbered Information (UI) Unicast (single DSP) Multicast (Multiple DSPs) roadcast (ll DSPs) Exchange Identification (XID) Test Type Services Protocol SSP DSP UI Unicast 8 Page 9

10 Type Services Protocol SSP DSPs UI Multicast 9 Type Services Protocol SSP UI DSPs roadcast Page

11 Type Services -- Connection Establishment SSP LLC LLC DSP U DM SME Type Services -- Flow Control vflow Control Methods Stop-and-Wait : Simple but not efficient enough Sliding Window u Send Window u Receive Window u Window Size. Page

12 Sliding Window Flow Control Sequence Number N(S): The sequence number of this PDU N(R): The sequence number the LLC sublayer entity expects to find in the next LLC-PDU it receives. This means that the PDUs with sequence number < N(R) have been received. l Send Window l Receive Window l Window Size N(R) N(S) Send Window = Page

13 Receive Window = Sliding Window N(R) N(S) Page

14 Sliding Window Operation Example v Two stations and v For station Window size of Send Window = Window size of Receive Window = v For station Window size of Send Window = Window size of Receive Window = v <= N(S),N(R) <= Initial condition Sliding Window Operation Example N(R) N(S) (a) sends a frame to (b) sends two frames to 8 Page

15 Sliding Window Operation Example N(R) N(S) N(R) N(S) N(R) N(S) (c) sends three frames to, the first one is lost (d) sends a frame to 9 Sliding Window Operation Example N(R) N(S) (e) retransmits the lost frame to (b) sends five frames to Page

16 Type Services Protocol DL-Data- CK.request DL-Data-CK- Status.indication DL-Data- CK.indication (a) Data Transmission (cknowledged) DL-Data- CK.request Status.indication (b) Data Transmission (Unacknowledged) Type Services Protocol DL-Reply.request Status.indication DL-Reply. indication (c) Reply Request (cknowledged) DL-Reply.request DL-Data-CK- DL-Reply- DL-Reply- Status.indication DL-Reply- Update.request DL-Reply- Update-Status.indication (d) Reply Request (Unacknowledged) (e) Reply Update Page

Microsoft Word - CVersion201412.doc

Microsoft Word - CVersion201412.doc On Socialistic Society 论社会主义社会中文版 Chinese Version 金宁 Ning JIN Copyright 2009 by Ning JIN ( 金宁 ). All right reserved. No part of this book may be used or reproduced, stored in a retrieval system,