![Page 1: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/1.jpg)
1COMP680E by M. Hamdi
Asynchronous Transfer Mode (ATM)
and QoS
![Page 2: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/2.jpg)
2COMP680E by M. Hamdi
ATM Era : Multiservice NetworksDeparture from Service Specialization
Multiservice Network
video
voice
bulkdata
interactivedata
![Page 3: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/3.jpg)
3COMP680E by M. Hamdi
Why ATM Did Not Make it the Way it was Initially Envisioned
Advantages of ATM
Disadvantages of ATM
Commercial Factors
• Single network optimized for everything (Data, phone, TV)
• Same technology for WAN, MAN, LAN (Seamless integration)
• QoS oriented and high-speed oriented
• Fast Hardware• Tremendous amount of research has been done
• Large overhead for packets
• QoS is a bit complicated from the applications point of view and network management point of view
• Not that great from web browsing (which is one killer application)
• Millions of networks already installed
• Lack of applications
• Expensive at the LAN (where it really matters)
• No strong business incentive for QoS (even up to now)
• Can achieve similar speed with an IP router as compared to an ATM switch (May be)
![Page 4: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/4.jpg)
4COMP680E by M. Hamdi
What is ATM?
ATM is packet switching!
• Switched or permanent connections
• Traffic type independent (voice, data, interactive video)
• Fixed length packet - 53 bytes (cell)
header payload
Fixed length packet = cell
![Page 5: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/5.jpg)
5COMP680E by M. Hamdi
ATM Cell Relay:The Underlying Technology
Cell Features Benefit
Small Low latency to support real-time services like audio and video (What is an appropriate size?)
Fixed Length Fast hardware switching and scalability
Standardized Usable in all networks (LAN and WAN)
Cells
Voice
Data
Video
![Page 6: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/6.jpg)
6COMP680E by M. Hamdi
Without Short Cells
Data packet(2000)
Voicepacket (50)
Router
Input
ports
Output
ports
A voice packet waits behind a large data packet
![Page 7: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/7.jpg)
7COMP680E by M. Hamdi
With Short Cells
Data #1(50)
Voice(50)
Data #40(50)
Router
Input
ports
Output
ports
Voice packet to be transmitted after Data #1
Data #2(50)
•Voice packet can go immediately after data packet #1
•Waiting for voice is reduced significantly
![Page 8: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/8.jpg)
8COMP680E by M. Hamdi
Virtual Paths & Virtual Channels
• Unique on a link-by-link basis• Virtual channels are contained within virtual paths• Interpreted at each switch to:
• determine output link• determine outgoing VPI/VCI
• Two-level structure:• allows “trunking” of virtual channels as one virtual path• virtual path can be switched• both used to route cells through network
PhysicalTransmission
LinkVCs VP
VCs VP
VCsVP
VCsVP
A Virtual Path (VP) describes the semi-permanent route between two end points. A Virtual Channel (VC) describes a cell transmission channel inside a virtual path
![Page 9: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/9.jpg)
9COMP680E by M. Hamdi
Connection Identifiers
![Page 10: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/10.jpg)
10COMP680E by M. Hamdi
ATM switch routing
ATMSwitch
ATMSwitch
ATMSwitch
ATMSwitch
ATMSwitch
VirtualPaths
VirtualCircuits
![Page 11: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/11.jpg)
11COMP680E by M. Hamdi
ATM Switches
• ATM switches translate VPI/VCI values
• VPI/VCI value unique only per interface—eg: locally significant and may be re-used elsewhere in network
45
2929
33
22
11
64642929
45
6464
2929
1
2
11
33
45
29
2929
6464
2
1
33
11
VPI/VCIPort VPI/VCIPort
Input Output
![Page 12: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/12.jpg)
12COMP680E by M. Hamdi
ATM Switching
Connections (routes) set up by software• Routing (path through multiple-switch network)
and resource allocation is performed once per connection by switch control CPU
Cells are switched by hardware• Hardware (table lookup + switching fabric)
switches each incoming cell to appropriate output port
• Once a connection is established, cells are not touched by software
![Page 13: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/13.jpg)
13COMP680E by M. Hamdi
VP and VC Switch
• Two types of ATM switch• VP switch does not look at VCIs, switching is based
on VPIs only• VCI does not change when passing through a VP
switch; VPI may change• VC switch looks at both VPI and VCI• VCI (as well as VPI) may change when passing
through a VC switch
![Page 14: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/14.jpg)
14COMP680E by M. Hamdi
Routing with a VP Switch
![Page 15: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/15.jpg)
15COMP680E by M. Hamdi
A Conceptual View of a VP Switch
![Page 16: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/16.jpg)
16COMP680E by M. Hamdi
Routing with a VC Switch
![Page 17: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/17.jpg)
17COMP680E by M. Hamdi
A Conceptual View of a VC Switch
![Page 18: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/18.jpg)
18COMP680E by M. Hamdi
ATM Protocol Stack
Upper LayersUpper Layers
ATM Adaptation LayerATM Adaptation Layer
ATM LayerATM Layer
Physical LayerPhysical Layer
![Page 19: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/19.jpg)
19COMP680E by M. Hamdi
ATM Architecture
Presentation
Session
Network
Data Link
PhysicalTransmission-convergencephysical medium dependent
Transport
Application
ATM Layer
ATM Adaptation Layer
Upper Layer Protocols
![Page 20: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/20.jpg)
20COMP680E by M. Hamdi
Adaptation Layers: Service Classes
![Page 21: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/21.jpg)
21COMP680E by M. Hamdi
Service Classes and Capacity of Network
![Page 22: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/22.jpg)
22COMP680E by M. Hamdi
QUEUES and PRIORITY
Classifier
CBR TrafficCBR Traffic
VBR TrafficVBR Traffic
UBR TrafficUBR Traffic
ABR TrafficABR Traffic
Ou
tpu
t
Priority 1
Priority 2
Priority 3
Priority 4
![Page 23: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/23.jpg)
23COMP680E by M. Hamdi
ATM Adaptation Layer: Summary
ServiceCategories
Class
ATM ATM Adaptation LayerAdaptation Layer
(AAL)(AAL)
ATM LayerATM Layer
Physical LayerPhysical Layer
Bit Rate ConnectionMode
TimingConcern
ApplicationExamples
• Bandwidth andBandwidth andthroughput guaranteedthroughput guaranteed
• Good for voice Good for voice and videoand video
AAL1A CBR(Constant)
Connection-Oriented
Yes
• Best effort bandwidth Best effort bandwidth and throughputand throughput
• Good for live video,Good for live video,multimedia, multimedia, LAN-to-LANLAN-to-LAN
AAL2B VBR(Variable)VBR-RT
andVBR-NRT
Connection-Oriented
Yes
• Best effort withBest effort withcongestion feedbackcongestion feedback
• Reliable delivery Reliable delivery of bursty traffic ifof bursty traffic iflatency okaylatency okay
AAL5C ABR(Available)
Connection-Oriented
No
• No guaranteeNo guarantee• For SMDS/LANFor SMDS/LAN
AAL3/4D UBR(Un-
specified)
Connection-less
No
![Page 24: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/24.jpg)
24COMP680E by M. Hamdi
QUALITY OF SERVICE
– Max CDT, Mean CTD, CDV, CLR, CER, SECBR, CMR
CBR rt-VBR nrt-VBR ABR UBR
PCR Yes Yes Yes Yes Yes
SCR N/A Yes Yes N/A N/A
MBS N/A Yes Yes N/A N/A
MCR No No No Yes No
CDVT(PCR) Yes Yes Yes Yes Yes
CDVT(SCR) N/A Yes Yes N/A N/A
![Page 25: COMP680E by M. Hamdi 1 Asynchronous Transfer Mode (ATM) and QoS](https://reader031.vdocuments.us/reader031/viewer/2022032310/56649d695503460f94a475a6/html5/thumbnails/25.jpg)
25COMP680E by M. Hamdi
Application Requirements
BandwidthBandwidth
DelayDelay
ReliabilityReliability
Cost ($ or Admin)Cost ($ or Admin)
• Peak Cell Rate (PCR)• Sustained Cell Rate (SCR)• Minimum Cell Rate (MCR)
• Peak Cell Rate (PCR)• Sustained Cell Rate (SCR)• Minimum Cell Rate (MCR)
• Cell Transfer Delay (CTD)• Cell Delay Variation (CDV)• Cell Transfer Delay (CTD)• Cell Delay Variation (CDV)
• Cell Loss Ratio (CLR)• Cell Loss Ratio (CLR)
• Link Weighting• Link Weighting