1 7/18/ :07 CS575ATM: ATM Layer1 Rivier College CS575: Advanced LANs ATM Technology: ATM Layer

2 7/18/ :07 CS575ATM: ATM Layer2 Overview 0 ATM Layer Functions 0 UNI ATM Cell Header Format 0 NNI ATM Cell Header Format 0 VP/VC/Transmission Path Concept 0 Virtual Channel and Virtual Path 0 ATM Switch Routing/Switching 0 ATM Virtual Path Switching 0 ATM Virtual Channel/Virtual Path Switching 0 Impact of Random Bit Errors on HEC Performance 0 Payload Type Indicator Encoding 0 Management Information Flows Jain

3 7/18/ :07 CS575ATM: ATM Layer3 ATM Layer Functions 0 Support Virtual Paths and Virtual Channels 0 Multiplexing/demultiplexing cell streams onto transmission path 0 Cell header generation/extraction 0 Provides cell routing functions (in ATM switch) 0 Performs VPI/VCI translation at switching nodes 0 Generic flow control 0 Traffic control and congestion control 0 Support a set of ATM layer Quality of Service (QoS) classes Higher Layers ATM Adaptation Layer (AAL) Convergence Sublayer (CS) Segmentation and Reassembly Sublayer (SAR) ATM Layer (ATM) Virtual Channel (VC) Virtual Path (VP) Physical Layer (PL) Transmission Convergence Sublayer (TC) Physical Medium Sublayer (PM)

4 7/18/ :07 CS575ATM: ATM Layer4 UNI ATM Cell Header Format Generic Flow Control (GFC) Virtual Path Identifier (VPI) Virtual Channel Identifier (VCI) Header Error Control (HEC) Payload Type (PT) Cell Loss Priority (CLP) Bit Octet Virtual Path Identifier (VPI) Virtual Channel Identifier (VCI)

5 7/18/ :07 CS575ATM: ATM Layer5 NNI ATM Cell Header Format Virtual Channel Identifier (VCI) Header Error Control (HEC) Payload Type (PT) Cell Loss Priority (CLP) Virtual Path Identifier (VPI) Virtual Channel Identifier (VCI) Bit Octet

6 7/18/ :07 CS575ATM: ATM Layer6 VP/VC/Transmission Path Concept Source: Stallings: Data and Computer Communications

7 7/18/ :07 CS575ATM: ATM Layer7 Virtual Channel and Virtual Path 0 A virtual channel (VC) is a concept used to describe unidirectional transport of ATM cells associated by a common unique identifier value 0 This identifier is called the virtual channel identifier (VCI) and is part of the cell header 0 A virtual channel link is a means of unidirectional transport of ATM cells between a point where a VCI value is assigned and the point where that value is translated or removed 0 A concatenation of VC links is called a virtual channel connection (VCC) 0 VCCs are provided for the purpose of user-user (workstation-workstation), user-network (workstation-switch), or network-network (switch-switch) information transfer 0 ATM cells are transported across the ATM network on VCCs 0 Cell sequence integrity is preserved for the cells belonging to the same VCC

8 7/18/ :07 CS575ATM: ATM Layer8 Virtual Channel and Virtual Path (Continued) 0 A virtual path (VP) is a concept used to describe unidirectional transport of ATM cells belonging to virtual channels that are associated by a common identifier value 0 This identifier is called the virtual path identifier (VPI) and is also part of the cell header 0 A virtual path link is terminated by the points where a VPI value is assigned and translated or removed 0 A concatenation of VP links is called a virtual path connection (VPC) 0 VPCs are provided for the purpose of user-user (workstation-workstation), user-network (workstation-switch), or network-network (switch-switch) information transfer 0 A VPC is a labeled path which can be used to transport a bundle of VCCs that have the same end points and to manage the resources used by these connections

9 7/18/ :07 CS575ATM: ATM Layer9 Virtual Channel and Virtual Path (Concluded) 0 If the VPCs are permanent or semi-permanent and have reserved capacity, establishing new VCCs requires simple connection admission decisions at the VPC terminators of existing VPCs 0 This would enable faster connection establishment since transit nodes are not involved in the connection set up 0 The virtual path concept also allows the possibility of segregating traffic types according to Quality of Service (QoS) requirements

10 7/18/ :07 CS575ATM: ATM Layer10 ATM Switch Routing/Switching

11 7/18/ :07 CS575ATM: ATM Layer11 ATM Virtual Path Switching Source: Stallings: Data and Computer Communications

12 7/18/ :07 CS575ATM: ATM Layer12 ATM Virtual Channel/Virtual Path Switching Source: Stallings: Data and Computer Communications

13 7/18/ :07 CS575ATM: ATM Layer13 Impact of Random Bit Errors on HEC Performance Stallings: Data and Computer Communications

14 7/18/ :07 CS575ATM: ATM Layer14 Payload Type Indicator Encoding PTI Coding Interpretation User data cell, congestion not experienced, SDU-type = 0 User data cell, congestion not experienced, SDU-type = 1 User data cell, congestion experienced, SDU-type = 0 User data cell, congestion experienced, SDU-type = 1 Segment OAM F5 flow related cell End-to-end OAM F5 flow related cell Reserved for future traffic control and resource management Reserved for future functions

15 7/18/ :07 CS575ATM: ATM Layer15 Management Information Flows 0 The ATM Layer management information is carried via F4 - F5 OAM cells 0 The OAM cell flow used for end-to-end management functions may be carried through the private ATM switch and made available to the users 0 The F4 flow is used for segment (link between ATM nodes) or VP end-to-end management at the VP level using VCIs 3 and 4 0 The F5 flow is used for segment (link between ATM nodes) or VC end-to-end management at the VC level using PTI code points 4 and 5

16 7/18/ :07 CS575ATM: ATM Layer16 W. Stalling, Local and Metropolitan Area Networks, 6 th edition, Prentice Hall, 2000, Chapter 11 References W. Stalling, Data and Computer Communications, 6 th edition, Prentice Hall, 2002, Chapters A. Wu, Advanced Local Area Networks, Lectures & Slides, Rivier College, 2001.