ATM Advanced Computer Networks ATM Outline ATM Introduction Motivation for ATM Architecture Design Assumptions ATM Adaptation Layers Old ATM Design Revised ATM Design AAL Details MPLS ID: 784701
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Slide1
Asynchronous Transfer Mode(ATM)
Advanced Computer
Networks
Slide2ATM OutlineATM IntroductionMotivation for ATM ArchitectureDesign AssumptionsATM Adaptation LayersOld ATM DesignRevised ATM DesignAAL DetailsMPLSAdvanced Computer Networks ATM2
Slide3ATM IntroductionITU-T lead the standards development.ATM Forum ensures interoperability among private and public ATM implementations.commonly used to implement WANs.DSL uses ATM for multiplexing and switching.used as a backbone in IP networks and Internet.DCC 9th
Ed.
Stallings
Advanced Computer Networks
ATM
3
Slide4Issues Driving LAN ChangesTraffic IntegrationVoice, video and data trafficMultimedia became the ‘buzz word’One-way batch Web trafficTwo-way batch voice messagesOne-way interactive Mbone broadcastsTwo-way interactive video conferencingQuality of Service guarantees (e.g. limited jitter, non-blocking streams)
LAN Interoperability
Mobile and Wireless nodes
Advanced Computer Networks
ATM
4
Slide5Stallings’ “High-Speed Networks”
Backbone
Advanced Computer Networks
ATM
5
Slide6Stallings’ “High Speed Networks” Advanced Computer Networks ATM
6
Slide7A/D
Voice
s
1 ,
s
2
…
Digital voice samples
A/D
Video
…
Compression
compressed frames
picture frames
Data
Bursty variable-length packets
cells
cells
cells
AAL
AAL
AAL
Leon-Garcia & Widjaja:
Communication Networks
A
TM
A
daptation
L
ayers
Advanced Computer Networks
ATM
7
Slide8MUX
Wasted bandwidth
ATM
TDM
4
3 2 1 4 3 2 1 4 3 2 1
4
3 1 3 2 2 1
Voice
Data packets
Images
Asynchronous Transfer Mode (ATM)
Leon-Garcia & Widjaja:
Communication Networks
Advanced Computer Networks
ATM
8
Slide9ATMATM standard (defined by CCITT) was widely accepted by common carriers as mode of operation for communication (particularly BISDN).ATM is a form of cell switching using small fixed-sized packets. Header
Payload
5 Bytes
48 Bytes
Basic ATM Cell Format
Advanced Computer Networks
ATM
9
Slide10ATM Conceptual ModelFour Design Assumptions 1. ATM network will be organized as a hierarchy.User’s equipment connects to networks via a UNI (User-Network Interface).Connections between provided networks are made through NNI (Network-Network Interface).2. ATM will be connection-oriented.
A connection (
an ATM channel
)
must be established before any cells are sent.
Advanced Computer Networks
ATM
10
Slide11ATM InterfacesDCC 9th Ed.StallingsAdvanced Computer Networks
ATM
11
Slide12ATM Connections two levels of ATM connections: virtual path connections (VPC) virtual channel connections (VCC)indicated by two fields in the cell header: virtual path identifier VPI virtual channel identifier
VCI
Advanced Computer Networks
ATM
12
Slide13ATM Virtual ConnectionsVirtual Path Connection (VPC)bundle of Virtual Channel Connections (VCC)
with same end
points.
DCC 9
th
Ed.
Stallings
Advanced Computer Networks
ATM
13
Slide14ATM Conceptual Model Assumptions (cont.)3. Vast majority of ATM networks will run on optical fiber networks with extremely low error rates.4. ATM must support low cost attachments.This decision lead to a significant decision: to prohibit cell reordering in ATM networks. ATM switch design is more difficult.
Advanced Computer Networks
ATM
14
Slide15ATM Cell FormatsDCC 9th Ed.Stallings
Advanced Computer Networks
ATM
15
Slide16Payload Type (PT) Field Coding
DCC 9
th
Ed.
Stallings
Advanced Computer Networks
ATM
16
Slide1723
N
1
Switch
N
1
…
5
6
video
25
video
voice
data
32
32
61
25
32
32
61
75
67
39
67
N
1
3
2
video
75
voice
67
data
39
video
67
…
…
ATM Cell Switching
Leon-Garcia & Widjaja:
Communication Networks
Advanced Computer Networks
ATM
17
Slide18c
ATM
Sw
1
ATM
Sw
4
ATM
Sw
2
ATM
Sw
3
ATM
DCC
a
b
d
e
VP3
VP5
VP2
VP1
a
b
c
d
e
Sw = switch
Digital Cross Connect
Only switches virtual paths
Leon-Garcia & Widjaja:
Communication Networks
Two Levels of ATM Switches
Advanced Computer Networks
ATM
18
Slide19ATM Protocol ArchitectureATM Adaptation Layers (AAL) – the protocol for packaging data into cells is collectively referred to as AAL.Must efficiently package higher level data such as voice samples, video frames and datagram packets into a series of cells.Design Issue: How many adaptation layers should there be?Advanced Computer Networks ATM
19
Slide20Plane management
Management plane
Control plane
User plane
Physical layer
ATM layer
ATM
Adaptation Layer
Higher layers
Higher layers
Layer management
ATM
Protocol Architecture
Leon-Garcia & Widjaja:
Communication Networks
Advanced Computer Networks
ATM
20
Slide21AAL
ATM
User information
User information
AAL
ATM
PHY
PHY
ATM
PHY
ATM
PHY
…
End system
End system
Network
ATM
in the Protocol Stack
Leon-Garcia & Widjaja:
Communication Networks
Advanced Computer Networks
ATM
21
Slide22Original ATM Architecture CCITT envisioned four classes of applications (A-D) requiring four distinct adaptation layers (1-4) which would be optimized for an application class:Constant bit-rate applications CBRVariable bit-rate applications VBR Connection-oriented data applicationsConnectionless data application
Advanced Computer Networks
ATM
22
Slide23ATM ArchitectureAn AAL was further divided into: Convergence Sublayer (CS) manages the flow of data to and from SAR sublayer.
Segmentation and Reassembly
Sublayer
(SAR)
breaks data into cells at the sender and reassembles
cells into larger data units at the receiver.
Advanced Computer Networks
ATM
23
Slide24Original ATM ArchitectureAdvanced Computer Networks ATM24
Slide25Transmission convergence sublayerPhysical medium dependent sublayer
Physical medium
ATM layer
Physical layer
Physical Layer ATM Adjustments
Advanced Computer Networks
ATM
25
Slide26The AAL interface was initially defined as classes A-D with SAP (Service Access Points) for AAL1-4.AAL3 and AAL4 were so similar that they were merged into AAL3/4.The data communications community concluded that AAL3/4 was not suitable for data communications applications. They pushed for standardization of
AAL5
(also referred to as SEAL – the Simple and Efficient Adaptation Layer).
AAL2
was not
initially
deployed.
Original
ATM Architecture
Advanced Computer Networks
ATM
26
Slide27Revised ATM ArchitectureAdvanced Computer Networks ATM
27
Slide28Revised ATM Service CategoriesClass
Description
Example
CBR
Constant Bit Rate
T1 circuit
RT-VBR
Real Time Variable Bit Rate
Real-time videoconferencing
NRT-VBR
Non-real-time Variable Bit Rate
Multimedia email
ABR
Available Bit Rate
Browsing the Web
UBR
Unspecified Bit Rate
Background file transfer
Advanced Computer Networks
ATM
28
Slide29QoS, PVC, and SVCQuality of Service (QoS) requirements are handled at connection time and viewed as part of signaling (e.g., RSVP). ATM provides permanent virtual connections and switched virtual connections.Permanent Virtual Connections (PVC) permanent connections set up manually by network manager.
Switched Virtual Connections (
SVC
)
set up and released
on demand
by the end user via signaling procedures.
Advanced Computer Networks
ATM
29
Slide30(b) CS PDU with pointer in structured data transferAAL 1 Pointer
1 Byte
46 Bytes
47 Bytes
optional
(a) SAR PDU header
CSI
SNP
Seq. Count
1 bit 3 bits
4
bits
AAL 1
Leon-Garcia & Widjaja:
Communication Networks
Advanced Computer Networks
ATM
30
Slide31…Higher layerUser data streamConvergence sublayer
SAR sublayer
ATM layer
CS PDUs
SAR PDUs
ATM Cells
47
47
47
1 47
1 47
1 47
H
H
H
5 48
H
5 48
H
5 48
H
b
1
b
2
b
3
AAL 1
Leon-Garcia & Widjaja:
Communication Networks
Advanced Computer Networks
ATM
31
Slide32(a) CPCS-PDU format(b) SAR PDU formatCPI Btag BASize
CPCS - PDU Payload
1 1 2 1 - 65,535
0-3 1 1 2
(
bytes)
(
bytes
)
(
bytes)
AL
Etag
Length
Pad
Header
Trailer
ST
SN
MID
SAR - PDU Payload
2
4 10 44 6 10
(bits
) (bytes) (
bits)
LI
CRC
Header (2 bytes)
Trailer (2 bytes)
AAL
3/4 CS
and SAR PDUs
Leon-Garcia & Widjaja:
Communication Networks
Advanced Computer Networks
ATM
32
Slide33Higher layerCommon part convergence sublayerSAR sublayerATM layer
Service specific convergence sublayer
Information
Assume null
T
PAD
User message
Pad message to multiple of 4 bytes. Add header and trailer.
Each SAR-PDU consists of 2-byte header, 2-byte trailer, and 44-byte payload.
H
4
4
2 44 2
2 44 2
2 44 2
…
…
Information
AAL 3/4
Leon-Garcia & Widjaja:
Communication Networks
Advanced Computer Networks
ATM
33
Slide34Information 0 - 65,535 0-47 1 1 2 4 (bytes) (bytes)UU CPI Length
CRC
Pad
Convergent Sublayer Format
SAR Format
48 bytes of Data
ATM
Header
1-bit end-of-datagram field (PTI)
AAL 5
Leon-Garcia & Widjaja:
Communication Networks
Advanced Computer Networks
ATM
34
Slide35Higher layerCommon part convergence sublayerSAR sublayerATM layer
PTI = 0
Service specific convergence
sublayer
Assume null
48 (1)
Information
T
PAD
…
…
Information
48 (0)
48 (0)
PTI = 0
PTI = 1
AAL 5
Leon-Garcia & Widjaja:
Communication Networks
Advanced Computer Networks
ATM
35
Slide36STM-1 (STS-3) Payload for SDH-Based ATM Cell TransmissionAdvanced Computer Networks ATM36
Slide37MPLS (Multi Protocol Label Switching)Advanced Computer Networks ATM37
Slide38The Nortel Networks Passport 8600 Routing Switchdesigned for high-performance Enterprise, carrier, and service provider networks. As a chassis based Ethernet switching platform, the Passport 8600 series provides wire speed L2-L7 traffic classification, filtering, forwarding and routing. Hardware based wire speed performance enables fast and efficient traffic classification, policy enforcement and filtering.Provides wire speed L2- L7 traffic classification.Advanced Computer Networks ATM38
Slide39The Nortel Networks Passport 8600 Routing SwitchMulti-layer redundancy with five 9’s reliabilityIntegrated intelligent bandwidth connectivity for 10/100/1000 Ethernet, ATM, PoS,10 Gig and WDMSeamless LAN/MAN/WAN connectivityEight policy enabled hardware queues per port512 Gigabits per second backplane switch capacity.Advanced Computer Networks ATM39
Slide40Nortel Ethernet Routing Switch 8600Avaya Switch ERS 8600
Configurable as a 1.440
Terabit
Switch cluster using
SMLT
10 Gigabit Ethernet
Packet Over SONET
6 OC-3 or 3 OC-12 ports
ATM
4 firewall or IDS
Advanced Computer Networks
ATM
40
Slide41ATM SummaryMotivation for ATM ArchitectureFour Design AssumptionsATM HierarchyUNI,NNI, VPI, VCI, two switch levelsOld ATM DesignConvergence Sublayer (CS), Segmentation and Reassembly Sublayer (SAR)ATM Adaptation LayersAAL1-4Advanced Computer Networks ATM
41
Slide42ATM SummaryNew ATM DesignPVC, SVCAAL DetailsAAL1, AAL3-4, AAL5Multi-Protocol Layer Switching (MPLS)Passport SwitchAdvanced Computer Networks ATM42