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7/29/2019 Lecture03 ATM
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NETNET 456456 High Speed NetworksHigh Speed Networks
1Reformatted slides from textbookData and Computer Communications, Ninth Edition by William Stallings,(c) Pearson Education - Prentice Hall, 2011 - Original Slides from Dr. Lawrie Brown
26-Nov-11
Lecture 03Chapter 11 Asynchronous Transfer Mode
Dr. Anis Koubaa
1
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Asynchronous Transfer ModeOne man had a vision of railways that would link all the
mainline railroad termini. His name was Charles Pearson and,
though born the son of an upholsterer, he became Solicitor tothe city of London. There had previously been a plan for gaslit
subway streets through which horse-drawn traffic could pass.
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown2
would become lurking places for thieves. Twenty years before
his system was built, Pearson envisaged a line running through
"a spacious archway," well-lit and well-ventilated.
His was a scheme for trains in a drain.King Solomon's Carpet,
Barbara Vine (Ruth Rendell)
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Outline
The Role of ATM
Protocol Architecture
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown3
ATM Cells
Transmission of ATM Cells
ATM Service Categories
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Learning Outcome
Understand how the ATM protocol works
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown4
n erstan ow ena es ata trans er at gspeeds
Be aware of ATM services
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The Role of ATM
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The Role of Asynchronous Transfer Mode
(ATM)
ATM is a switching and multiplexing technology
ATM uses fixed-length packets called cells connection-oriented (Virtual Circuits)
erformance of a circuit-switchin network and the
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown6
flexibility and efficiency of a packet-switching network supports data, voice, video
ATM network makes reservations and preplans routes
transmission based on priority and QoS
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ATM
ITU-T leading the development of standards
ATM Forum ensures interoperability among private and
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown7
commonly used to implement WANs
DSL uses ATM for multiplexing and switching
used as a backbone in IP networks and Internet
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ATM a streamlined packet transfer interface
similarities to packet switching and frame relay
transfers data in discrete chunks
supports multiple logical connections over a single physical interface
ATM uses fixed sized packets called cells
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown8
minimal error and flow control capabilities reduces the overhead of processing ATM cells
reduces the number of overhead bits required with each cell,
ATM operate at high data rates
The data rates specified at the physical layer range from 25.6 Mbps
to 622.08 Mbps.
Other data rates, both higher and lower, are possible.
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Protocol Architecture
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Protocol ArchitecturePhysical Layer
Specifies how the signal is
transmitted and encoded in atransmission medium.
ATM Layer
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown10
in fixed-size cells and how of logicalconnections are used
ATM Adaptation Layer (AAL)
(1) maps data of higher-layer intoATM cells to be transported overan ATM network,
(2) collects data from ATM cells fordelivery to higher layers.
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ATM Network Interfaces
switches are interconnected by point-to-point ATM links
called interfaces
user-networkinterface (UNI)
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown12
network node interface (NNI) interface specification includes:
definition of link types allowed
addressing formats
cell format
control signaling protocols
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ATM
I
N
T
E
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown13
RF
A
C
ES
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ATM Lo ical Connections
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ATM Logical Connections
analogous to virtual circuit in X.25
virtual channel connections (VCC)
basic unit of switching between two end users
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown15
variable rate full duplex flow
fixed-size cells
user-network exchange (control signaling)
network-network exchange (network management and routing)
VCCs also used for
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ATM Connection Establishment
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown16
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ATM Virtual Path Connection Virtual Path Connection (VPC)
bundle of VCCs with same end points
Why VPC is needed? reduce the control cost by grouping connections sharing the
same path
the management of a small number of groups of connections
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown17
(paths) is easier than the management of a large number ofconnections
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Advantages of Virtual PathsVirtual paths have several advantages
- simplified network architecture
- increased network erformance
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown18
and reliability- reduced processing and shortconnection setup time
- enhanced network services: usergroups definition
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Virtual Path/Virtual Channel Terminology
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown19
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Call Establishment Using VPs Virtual path connection set-up
process is decoupled from the processof setting up an individual virtualchannel connection
The virtual path control mechanismsinclude
calculating routes,
allocating capacity, and
storing connection state information.
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown20
To set up a virtual channel, there mustfirst be a virtual path connection tothe required destination node withsufficient available capacity to supportthe virtual channel, with theappropriate QoS
A virtual channel is set up by storingthe required state information (virtualchannel/virtual path mapping).
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Virtual Channel CharacteristicsQuality-of-Service (QoS)
A user of a VCC is provided with a QoS (e.g. cell loss ratio and cell delay variation(Jitter).
Switched and semi-permanent channel connections
Switched VCC (SVC) is an on-demand connection: requires a call control signaling forsetup and termination.
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown22
em ermanen s a connec on o ong ura on: s se up y
configuration or network management action
cell sequence integrity
the sequence of transmitted cells within a VCC is preserved.
traffic parameter negotiation and usage monitoring Traffic parameters can be negotiated between user and network for each VCC (e.g.
average rate, peak rate, burstiness, and peak duration)
The network monitors cells in the VCC to ensure negotiated parameters are notviolated.
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Control Si nalin in ATM
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Control Signaling - VCC In ATM, a Control Signaling mechanism is needed for
the establishment and release of VPCs and VCCs.
Control signaling uses separate connections from thoseused for data.
One or a combination of these methods can be used in
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown25
any part cu ar networ :
1. semi-permanent VCC: no need for control signaling
2. meta-signaling channel: low data rate, permanent channelfor exchanging control signaling information
1. user-to-network signaling virtual channel: used to set up VCCsbetween user and network. VCC will be used to carry data
2. user-to-user signaling virtual channel : used to set up VCCsbetween users. It must be setup within a pre-established PVC
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Control Signaling - VPC methods for control signaling for VPCs:
1. semi-permanent
2. customer controlled: the customer uses a signaling VCC torequest the VPC from the network
3. network controlled: the network establishes a VPC for its
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown26
. - - ,
user-to-network, or user-to-user
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ATM Signaling Protocols
used between end system and switch across UNIlinks
UNI si nalin in ATM defines the rotocol b which
UNI signaling
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown27
switched VCCs (SVC) are established and releaseddynamically by the ATM devices in the network.
used between switches across NNI links
includes both signaling and routing
NNI signaling
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ATM Cells
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ATM Cells ATM use of fixed-size cells,
consisting of a 5-octetheader and a 48-octet
information field. Advantages to the use of
small, fixed-size cells.
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown29
t e use o sma ce s mayreduce queuing delay for ahigh-priority cell,
fixed-size cells can beswitched more efficiently
it is easier to implement theswitching mechanism inhardware
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ATM Header Fields generic flow control (GFC)
used for control of cell flow only at the user-network interface
used to assist the customer in controlling the flow of traffic for different
QoS (alleviate short-term overload condition). virtual path identifier (VPI)
used for routing: 8 bits in user interface and 12 bits in network interface.
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown30
v r ua c anne en er
used for routing to and from the end users.
payload type (PT)
Type of data in the information field (data) see Table 11.2
cell loss priority (CLP)
One bit that provides guidance to the network in congestion situation
header error control (HEC)
used for both error control and synchronization
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Payload Type (PT) Field Coding
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown31
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ATM Cells
Generic Flow Control
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Generic Flow Control (GFC) control traffic flow at user to network interface
(UNI) to alleviate short term overload
two sets of procedures are used (at the UNI)
uncontrolled transmission
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown33
every connection subject to flow control or not
if subject to flow control:
may be one group (A) default: one-queue model
may be two groups (A and B): two-queue model
flow control is from subscriber to network
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GFC - Single Group of Connections1. IfTRANSMIT=1 send uncontrolled cells any time. If
TRANSMIT=0 no cells may be sent
2. IfHALT received,TRANSMIT=0 until NO_HALT3. IfTRANSMIT=1 & no uncontrolled cell to send:
>
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown34
. _
decrement GO_CNTR2. IfGO_CNTR=0, TE may not send controlled cells
4. TE sets GO_CNTR to GO_VALUE upon receiving
SET signal
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Use of HALT
to limit effective data rate on ATM
should be cyclic
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown35
to re uce ata rate y a , ssue to e n e ect
50% of time
done on regular pattern over lifetime of connection
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Generic Flow Control (GFC) Field Coding
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown36
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Two Queue Model
uses two counters each with current and initial values:
GO_CNTR_A
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown37
_ _
GO_CNTR_B
GO_VALUE_B
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ATM Cells
Header Error Control
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Header Error Control
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown40
Effect of
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Effect of
Error in Cell Header
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown41
Impact of Random Bit Errors on HEC
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Impact of Random Bit Errors on HEC
Performance
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown42
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ransmission of ATM Cells
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Transmission of ATM Cells
I.432 specifies
several data rates:
two choices of
transmissionstructure:
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown44
.
155.52Mbps
51.84Mbps
25.6Mbps
layer
SDH basedphysical layer
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ransmission of ATM Cells
Cell-based Physical Layer
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Cell Based Physical Layer
No framing is needed
The interface structure consists of a continuous stream
of 53-octet cells Synchronization is achieved on the basis of the HEC field
in the cell header
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown46
cell delineation based on header error control field
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Cell Delineation State Diagram
HUNT state: a cell delineation
algorithm is performed bit by bit
to determine if the HEC coding
law is observed (i.e., matchbetween received HEC and
calculated HEC). Once a match is
achieved, it is assumed that one
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown47
header has been found, and the
method enters the PRESYNCstate.
PRESYNC state: a cell structure is
now assumed. The cell delineation
algorithm is performed cell by celluntil the encoding law has been
confirmed consecutively d times.
SYNC state: the HEC is used for
error detection and correction.
Cell delineation is assumed to be
lost if the HEC coding law is
recognized consecutively as
incorrect a times.
Impact of Random Bit Errors on Cell
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Impact of Random Bit Errors on Cell
Delineation Performance
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown48
Acquisition Time
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Acquisition Time
vs. Bit Error Rate
NET 456: High Speed Networks, by Dr. Anis KoubaaTextbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown49
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SDH Based Physical Layer
it imposes structure on ATM stream (framing)
eg. for 155.52Mbps
use STM-1 (STS-3) frame
NET 456: High Speed Networks, by Dr. Anis Koubaa Textbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown51
can carry an pay oa s
specific connections can be circuit switched using SDH
channel
SDH multiplexing techniques can combine several ATM
streams
STM-1 Payload for SDH-Based ATM Cell
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y
Transmission
NET 456: High Speed Networks, by Dr. Anis Koubaa Textbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown52
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Advantages of the SDH-based approach
Ability to carry both ATM-based or STM-based (synchronoustransfer mode) payloads,
Some specific connections can be circuit switched using an
SDH channel. For example, a connection carrying constant-bit-rate video traffic can
be mapped into its own exclusive payload envelope of the STM-1signal, which can be circuit switched. This may be more efficient than
NET 456: High Speed Networks, by Dr. Anis Koubaa Textbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown53
ATM switching.
Ability to combine several ATM streams to build interfaceswith higher bit rates than those supported by the ATM layer ata particular site. For example, four separate ATM streams, each with a bit rate of 155
Mbps (STM-1), can be combined to build a 622-Mbps (STM-4)interface.
This arrangement may be more cost effective than one using a single622-Mbps ATM stream.
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ATM Service Cate ories
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Constant Bit Rate (CBR)
fixed data rate continuously available
tight upper bound on delay
NET 456: High Speed Networks, by Dr. Anis Koubaa Textbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown56
uncompressed audio and video
video conferencing
interactive audio
A/V distribution and retrieval
Real-Time Variable Bit Rate
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(rt-VBR)
for time sensitive applications tightly constrained delay and delay variation
rt-VBR applications transmit data at a rate that varies
NET 456: High Speed Networks, by Dr. Anis Koubaa Textbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown57
with time
characterized as bursty
allow more flexibility than CBR
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Non-Real-Time Variable Bit Rate (nrt-VBR)
used for data transfers with critical response time airline reservations, banking transactions
NET 456: High Speed Networks, by Dr. Anis Koubaa Textbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown58
en system spec es: a peak cell rate
a sustainable or average cell rate
measure of how bursty or clumped cells can be
U ifi d Bi R (UBR)
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Unspecified Bit Rate (UBR)
may be additional capacity over and above that usedby CBR and VBR traffic not all resources dedicated to CBR/VBR traffic
unused cells due to bursty nature of VBR for application that can tolerate some cell loss or
variable delays
NET 456: High Speed Networks, by Dr. Anis Koubaa Textbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown59
eg. TCP based traffic
cells forwarded on FIFO basis
best effort service
examples: text/data/image transfer telecommuting
A il bl Bi R (ABR)
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Available Bit Rate (ABR)
application specifies peak cell rate (PCR) and minimumcell rate (MCR)
NET 456: High Speed Networks, by Dr. Anis Koubaa Textbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown60
spare capacity shared among all ARB sources
eg. LAN interconnection
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G t d F R t (GFR)
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Guaranteed Frame Rate (GFR)
better service for frame based traffic
IP, Ethernet
NET 456: High Speed Networks, by Dr. Anis Koubaa Textbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown62
goal is to optimize traffic passing from LAN onto an ATMbackbone network
large enterprise, carrier, Internet service providers
allows user to reserve capacity for each GFR VC
Summary
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Summary
role of Asynchronous Transfer Mode (ATM) protocol architecture
NET 456: High Speed Networks, by Dr. Anis Koubaa Textbook: Data and Computer Communications, 9/EBy Williams Stalling Original Slides from Dr. Lawrie Brown63
virtual path/virtual channel
ATM Cell format
transmission of ATM cells
ATM services