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8/13/2019 ATM ATM Layer.ppt
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CS575 ATM: ATM Layer 1
14/11/2013 10:10
Rivier College
CS575: Advanced LANs
ATM Technology: ATM Layer
8/13/2019 ATM ATM Layer.ppt
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CS575 ATM: ATM Layer 2
24/11/2013 10:10
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
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CS575 ATM: ATM Layer 3
34/11/2013 10:10
ATM Layer Functions
0 Support Virtual Paths and Virtual Channels0 Multiplexing/demultiplexing cell streams onto transmission path0 Cell header generation/extraction0 Provides cell routing functions (in ATM switch)0 Performs VPI/VCI translation at switching nodes0 Generic flow control0 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 ReassemblySublayer SAR)
ATM Layer ATM) Virtual Channel VC)Virtual Path VP)
Physical Layer PL)Transmission Convergence Sublayer TC)
Physical Medium Sublayer PM)
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CS575 ATM: ATM Layer 4
44/11/2013 10:10
UNI ATM Cell Header Format
Generic Flow Control GFC) Virtual Path Identifier VPI)
Virtual Channel Identifier VCI)
Header Error Control HEC)
8 7 6 5 4 3 2 1
Payload Type PT)CellLossPriority CLP)
Bit
Octet 1
2
3
4
5
Virtual Path Identifier VPI)
Virtual Channel Identifier VCI)
Virtual Channel Identifier VCI)
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CS575 ATM: ATM Layer 5
54/11/2013 10:10
NNI ATM Cell Header Format
Virtual Channel Identifier VCI)
Header Error Control
HEC)
8 7 6 5 4 3 2 1
Payload Type PT)CellLossPriority CLP)
Virtual Path Identifier VPI)
Virtual Path Identifier VPI)
Virtual Channel Identifier VCI)
Virtual Channel Identifier VCI)
Bit
Octet
1
2
3
4
5
6
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CS575 ATM: ATM Layer 6
64/11/2013 10:10
VP/VC/Transmission Path Concept
Source: Stallings: Data and Computer Communications
74/11/2013 10 10
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CS575 ATM: ATM Layer 7
74/11/2013 10:10
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 VCCs0 Cell sequence integrity is preserved for the cells belonging to the same VCC
84/11/2013 10:10
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CS575 ATM: ATM Layer 8
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Virtual Channel and Virtual Path (Continued)
0 A virtual path (VP) is a concept used to describe unidirectional transport ofATM 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
94/11/2013 10:10
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CS575 ATM: ATM Layer 9
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Virtual Channel and Virtual Path (Concluded)
0 If the VPCs are permanent or semi-permanent and have reservedcapacity, establishing new VCCs requires simple connectionadmission decisions at the VPC terminators of existing VPCs
0 This would enable faster connection establishment since transitnodes are not involved in the connection set up
0
The virtual path concept also allows the possibility of segregatingtraffic types according to Quality of Service (QoS) requirements
104/11/2013 10:10
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CS575 ATM: ATM Layer 10
ATM Switch Routing/Switching
114/11/2013 10:10
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CS575 ATM: ATM Layer 11
ATM Virtual Path Switching
Source: Stallings: Data and Computer Communications
124/11/2013 10:10
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CS575 ATM: ATM Layer 12
ATM Virtual Channel/Virtual Path Switching
Source: Stallings: Data and Computer Communications
134/11/2013 10:10
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CS575 ATM: ATM Layer 13
Impact of Random Bit Errors on HECPerformance
Stallings: Data and Computer Communications
144/11/2013 10:10
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CS575 ATM: ATM Layer 14
Payload Type Indicator Encoding
PTI
Coding Interpretation
000
001
010
011
100
101
110
111
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 = 0User data cell, congestion experienced,SDU-type = 1
Segment OAM F5 flow relatedcellEnd-to-end OAM F5 flow relatedcell
Reserved for future traffic control and resourcemanagementReserved for futurefunctions
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CS575 ATM: ATM Layer 15
Management Information Flows
0 The ATM Layer management information is carried via F4 - F5OAM cells
0 The OAM cell flow used for end-to-end management functionsmay be carried through the private ATM switch and madeavailable to the users
0 The F4 flow is used for segment (link between ATM nodes) or VPend-to-end management at the VP level using VCIs 3 and 4
0 The F5 flow is used for segment (link between ATM nodes) orVC end-to-end management at the VC level using PTI codepoints 4 and 5
164/11/2013 10:10
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CS575 ATM: ATM Layer 16
W. Stalling, Local and Metropolitan Area Networks, 6th edition,
Prentice Hall, 2000, Chapter 11
References
W. Stalling, Data and Computer Communications, 6th edition,Prentice Hall, 2002, Chapters 11-12
A. Wu, Advanced Local Area Networks, Lectures & Slides, RivierCollege, 2001.