ECE544: Communication Networks-II, Spring 2013 - PowerPoint PPT Presentation

Loading...

PPT – ECE544: Communication Networks-II, Spring 2013 PowerPoint presentation | free to download - id: 5ce147-MGZiN



Loading


The Adobe Flash plugin is needed to view this content

Get the plugin now

View by Category
About This Presentation
Title:

ECE544: Communication Networks-II, Spring 2013

Description:

ECE544: Communication Networks-II, Spring 2013 D. Raychaudhuri Lecture 3 Includes teaching materials from J. Kurose, L. Peterson and ATM Forum tutorials – PowerPoint PPT presentation

Number of Views:71
Avg rating:3.0/5.0
Slides: 71
Provided by: d303
Category:

less

Write a Comment
User Comments (0)
Transcript and Presenter's Notes

Title: ECE544: Communication Networks-II, Spring 2013


1
ECE544 Communication Networks-II, Spring 2013
  • D. Raychaudhuri
  • Lecture 3

Includes teaching materials from J. Kurose, L.
Peterson and ATM Forum tutorials
2
Todays Lecture
  • Switched Networks
  • Switching Concepts
  • Ethernet Switches
  • Learning bridge
  • Spanning tree
  • Multicast
  • Asynchronous Transfer Mode (ATM) Network
  • Overview
  • Virtual Circuit Switching
  • Virtual Circuit and Virtual Path
  • ATM AAL
  • ATM Quality of Service (QoS)
  • Leaky Bucket Algorithm
  • Switch Implementation

3
Intro to Switching
  • Build a large network by interconnecting a number
    of switches
  • Easily add new hosts
  • Switching Techniques
  • Datagram or connectionless (Ethernet)
  • Unique address
  • No need to setup connection
  • Virtual circuit or connection-oriented (ATM)
  • Set up connection and maintain connection state
  • Source routing
  • Source specify the whole or partial route to the
    destination

4
Ethernet Hub
  • Hub is just a repeater
  • Receive signal from one port and broadcast to all
    other ports
  • Extends max distance between nodes, but
    collisions are propagated
  • Individual segment collision domains become one
    large collision domain
  • Cannot interconnect different LAN technologies,
    e.g. 10BaseT 100BaseT

5
Bridges/LAN switches
  • Link layer device
  • stores and forwards frames
  • examines frame header and selectively forwards
    frame based on MAC dest address
  • when frame is to be forwarded on segment, uses
    the corresponding MAC to access segment (e.g.
    CSMA/CD for Ethernet)

Switch
hub
hub
hub
6
Bridges/LAN switches (Cont.)
  • Interconnect multiple LANs, possibly even support
    different IEEE 802.x types, e.g. 802.3 and 802.5,
    802.11, but NOT 802.x with ATM

Bridge
7
Ethernet Hubs vs. Ethernet Switches
  • An Ethernet switch is a packet switch for
    Ethernet frames
  • Buffering of frames prevents collisions
  • Each port is isolated and builds its own
    collision domain
  • Break subnet into LAN segments
  • Host can directly connect to switch, no
    collision, full duplex
  • An Ethernet Hub does not perform buffering
  • Collisions occur if two frames arrive at the same
    time.

Hub
Switch
8
A Switched Enterprise Network
Router
Switch
9
Forwarding
Forwarding Table Forwarding Table Forwarding Table
Destination Port Time-to-Live (TTL)
A 3 2
B 0 4
C 3 2
D 3 4
E 2 5
F 1 1
G 0 4
H 0 5
  • Which port to forward a frame?
  • Use forwarding database/table
  • lt MAC address, port, Time-to-Live (TTL)gt
  • How to build the forwarding table???
  • A routing problem

10
Transparent Bridges
Three parts to transparent bridges (1)
Learning of Addresses (2) Forwarding of
Frames (3) Spanning Tree Algorithm
11
Self Learning (Learning Bridges)
  • Forwarding tables entries are set automatically
    with a simple heuristic
  • The source address field of a frame that arrives
    on a port tells which host is reachable from this
    port.
  • When a frame received, switch learns location
    of sender
  • records sender/location pair in forwarding table
    with TTL MAX_TTL
  • TTL reset to MAX_TTL every time a frame with the
    same source addr is received to refresh the
    existing table entry
  • Entry removed when TTL counts down to 0

12
Frame Forwarding/Filtering
  • When switch receives a frame
  • index forwarding table using MAC dest address
  • if entry found for destinationthen
  • if dest on the same port from which frame
    arrived then drop the frame (filtering)
  • else forward the frame on port
    indicated
  • else flood

Forward on all but the port on which the frame
arrived
13
Example
  • Consider the following packets (SrcA, DestF),
    (SrcC, DestA), (SrcE, DestC)
  • What have the bridges learned?

14
Danger of Loops
  • Consider the two LANs that are connected by two
    bridges.
  • Assume host n is transmitting a frame F with
    unknown destination.
  • What is happening?
  • Bridges A and B flood the frame to LAN 2.
  • Bridge B sees F on LAN 2 (with unknown
    destination), and copies the frame back to LAN 1
  • Bridge A does the same.
  • The copying continues

F
15
Spanning Trees / Transparent Bridges
  • A solution is to prevent loops in the topology
  • IEEE 802.1d has an algorithm that organizes the
    bridges as spanning tree in a dynamic environment
  • Note Trees dont have loops
  • Bridges that run 802.1d are called transparent
    bridges

16
Spanning Tree Protocol (STP)
  • Each bridge has a unique ID (MAC addr priority
    level)
  • Select the bridge with the smallest ID as the
    root of the spanning tree, called root bridge
  • All the ports on the root bridge are active
    (forwards the frames)
  • Each bridge determines the minimum-cost path from
    itself to the root and nodes which of its port is
    on the path (root port)
  • Link cost the cost of traversing a single
    network segment (link)
  • Path cost the sum of the costs of the segments
    (links) on the path
  • an administrator can configure the cost of
    traversing a particular segment (link)
  • E.g. set the cost for every segment to 1, the
    path cost is a count of the number of bridges
    along the path.
  • Root path cost the cost of the minimum-cost path
    from this bridge to the root
  • Root port the port connecting to the
    minimum-cost path on this bridge
  • Breaking ties When multiple paths from a bridge
    are min-cost paths, choose the path using the
    neighbor bridge with the lower bridge ID.
  • If the multiple ports connects this bridge and
    the neighbor bridge on the root path, choose the
    port with the lowest port ID as the root port.

17
Spanning Tree Protocol (Cont.)
  • Select a single designated bridge and its
    designated port on each LAN segment
  • Designated bridge the bridge on that LAN segment
    with the minimum-cost path to the root. Only
    designated bridge allowed to forward frames to
    and from this LAN segment.
  • If two or more bridges have the same root path
    cost, choose the one with the lowest bridge ID
  • Designated port the port connecting the
    designated bridge to this LAN segment
  • If the designated bridges has two or more ports
    attached to this LAN, choose the port with the
    lowest port ID
  • Any port that is not a root port or a designated
    port is blocked.

18
Spanning Tree Protocol (Cont.)
  • Bridges exchange messages to configure the bridge
    (Configuration Bridge Protocol Data Unit, CBPDUs)
    to cut the loop and build the tree.
  • Source addr port MAC addr, Dest. addr STP
    multicast address
  • ltsending bridge ID, root bridge ID, root path
    costgt
  • At the beginning, each bridge considers itself to
    be the root, sends CBPDU identifying itself as
    root
  • Upon receiving a CBPDU, check if the new path is
    better
  • if better, update its STP record, forward the
    message after updating the root path cost in the
    message
  • After stabilization, only the root bridge
    generates new CBPDUs regularly, others stops
    generate CBPDUs once learning it is not a root
  • From a non-root port, receives a CBPDU indicating
    it is not the designated bridge for that segment,
    goes to blocking state
  • BPDU is still received in blocking state.

19
Spanning Tree Protocol Example
A
B
  1. B3 receives (B2,0,B2)
  2. Since 2lt3, B3 accepts B2 as root
  3. B3 adds 1 to distance advertised by B2 and sends
    (B2,1,B3) to B5
  4. Meanwhile B2 accepts B1 as root because it has
    lower ID and sends (B1,1,B2) to B3
  5. B5 accepts B1 as root and sends (B1,1,B5) towards
    B3
  6. B3 accepts B1 as root and it notes that both B2
    and B5 are closer to the root than it is.
  7. B3 stops fowarding messages on both its interfaces

K
C
D
F
E
H
G
J
I
20
Virtual LAN
  • Group the stations in a broadcast domain,
    regardless of their physical location.
  • A VLAN ID (VID) in the frame
  • A frame is not forwarded/broadcasted from one
    VLAN to another VLAN
  • Each VLAN establishes its own spanning tree
  • Assign a port to one or multiple or all VLANs
    (static or dynamic)

Host B
Host A
VLAN 100
VLAN 100
VLAN 200
VLAN 200
Host D
Host C
21
Asynchronous Transfer Mode (ATM) Network
  • Overview
  • Virtual Circuit Switching
  • Virtual Circuit and Virtual Path
  • ATM AAL
  • ATM Quality of Service (QoS)
  • Leaky Bucket Algorithm
  • Switch Implementation

22
ATM Introduction
  • 1990s standards for high-speed (155Mbps to 622
    Mbps and higher) Broadband Integrated Service
    Digital Network (BISDN) architecture
  • Goal integrated, end-end transport of carry
    voice, video, data
  • meeting timing/quality of service (QoS)
    requirements of voice, video (versus Internet
    best-effort model)
  • next generation telephony technical roots in
    telephone world
  • packet-switching (fixed length packets, called
    cells) using virtual circuits

23
ATM Vision
The Ultimate Integrated Services Network
  • ATM network moves cells (fixed length packets)
    with low delay and low delay variation at high
    speeds
  • Devices at ends translate (e.g., segment and
    reassemble) between cells and original traffic

24
ATM Basic Concepts
  • Negotiated Service Connection
  • End-to-end connections, called virtual circuits
  • Traffic contract
  • Virtual circuit based switching
  • Dedicated capacity
  • Cell Based
  • Small, fixed length

A
25
Negotiated Service Connection
Traffic Contract
  • Parameters
  • Traffic Characteristics
  • Peak Cell Rate
  • SustainableCell Rate
  • Quality of Service
  • Delay
  • Cell Loss

Virtual Connection 1-QOS A Virtual Connection
1-QOS B Virtual Connection 1-QOS b
26
ATM System Architecture
A
27
The ATM Cell
Header
Payload
5 Bytes
48 Bytes
  • Small Size (low delay, but high overhead)
  • 5 Byte Header
  • 48 Byte Payload
  • Fixed Size (easy switch implementation, but
    padding overhead)
  • Header contains virtual circuit information
  • Payload can be voice, video or other data types

A
28
ATM Adaptation Layer (AAL)
  • Only at edge of ATM network (end system)
  • Roughly analogous to Internet transport layer
  • Provides mapping Of applications (IP or native
    ATM applications) to ATM service of the same type
  • Segments/Reassembles into 48 Payloads
  • Hands 48 Byte Payloads To ATM Layer

A
29
ATM Layer
48-Byte Payloads From AAL
5-Byte Header

53-Byte Cell To Physical Layer
Header Contains Virtual Path and Channel
Identifiers
  • Adds/Removes Header To 48 Byte Payload
  • Header Contains Connection Identifier,
    multiplexes 53 Byte cells into virtual
    connections,
  • ATMs Network layer
  • Transport cells across ATM network (analogous to
    IP network layer, but very different strategy and
    services than IP network layer)
  • Signaling, cell switching, routing

A
30
Physical Layer
Cable Plants
Speed Matching and Framing
Uses Existing Media Twisted Pair Coax Fiber
-Multimode -Single Mode
Wide Range of Speeds LAN, MAN, WAN Compatibility
Transmission Frame
A
31
ATM PHY Two Sublayers
  • Transmission Convergence Sublayer (TCS) adapts
    ATM layer above to PMD sublayer below
  • Specific to the PMD
  • Cell delineation
  • Cell rate decoupling, inserting idle (empty)
    cells when no data cells to send (with
    unstructured PMD sublayer)
  • Physical Layer Medium Dependent Sublayer (PMD)
    depends on physical medium being used
  • Probably use existing standards and technology
  • Medium, line code, connectors

32
ATM Physical Layer (Cont.)
  • Physical Medium Dependent (PMD) sublayer
  • SONET/SDH transmission frame structure (like a
    container carrying bits)
  • bit synchronization
  • bandwidth partitions (TDM)
  • several speeds OC3 155.52 Mbps OC12 622.08
    Mbps OC48 2.45 Gbps, OC192 9.6 Gbps
  • TI/T3transmission frame structure (old telephone
    hierarchy) 1.5 Mbps/ 45 Mbps
  • unstructured just cells (busy/idle)

33
155 Mbps, SONET STS-3c/SDH STM-1
270 columns
9 R o w s
. . .
Maintenance and operations
1 Synchronous Payload Envelope (1 column of
overhead)
125 msec
9 bytes
  • 9 260 8/125 msec 149.76 Mbps payload

A
34
ATM network or link layer?
  • Vision provide the end-to-end transport ATM
    from desktop to desktop
  • ATM is network technology
  • Reality used to connect IP backbone routers
  • IP over ATM
  • ATM as switched link layer, connecting IP routers

35
ATM Interfaces
PrivateNNI
Public NNI
PrivateUNI
Metropolis Data Services Inc.
PublicUNI
ATMDXI
FUNI
FUNI
B-ICI
  • UNI User Network Interface
  • NNI Network Node Interface
  • B-ICI BISDN Inter-Carrier Interface
  • ATM DXI Data eXchange Interface
  • FUNI ATM Frame Based UNI Interface

Country Wide Carrier Services
D
36
ATM UNI Cell
7
6
5
4
3
2
1
0
Generic Flow Control
Virtual Path Identifier
Virtual Path Identifier
Virtual Channel Identifier
Virtual ChannelIdentifier
5 Byte Header
Virtual Channel Identifier
Virtual ChannelIdentifier
Payload Type Identifier
CLP
Header ErrorCheck
48 Byte Payload
Payload(48 bytes)
CLP Cell Loss Priority
37
ATM NNI Cell
7
6
5
4
3
2
1
0
Virtual Path Identifier
Virtual Path Identifier
Virtual Channel Identifier
Virtual ChannelIdentifier
5 Byte Header
Virtual Channel Identifier
Virtual ChannelIdentifier
Payload Type Identifier
CLP
Header ErrorCheck
48 Byte Payload
Payload(48 bytes)
CLP Cell Loss Priority
38
Generic Flow Control
  • Used for UNI only - Not NNI
  • Currently undefined
  • Set to 0000B
  • Proposed future uses
  • Flow control
  • Shared media multiple access

B
39
Payload Type Identifier (PTI)
  • Bit 3 Used to discriminate data cells from
    operation, administration, maintenance cells.
  • Bit 2 Used to indicate congestion in data cells
    (Bit 3 0)
  • Set by Switches
  • Source and Destination Behavior Defined for
    Available Bit Rate Flow Control VCCs
  • Bit 1 Carried transparently end-to-end in data
    cells
  • Used by AAL5

C
40
Cell Loss Priority
  • Cells with bit set (CLP 1) should be discarded
    before those with bit not set (low priority)
  • Can be set by the terminal
  • Can be set by ATM switches for internal network
    control
  • Virtual channels/paths with low quality of
    service
  • Cells that violate traffic management contract
  • Key to ATM Traffic Management

41
Header Error Check
7
6
5
4
3
2
1
0
Generic Flow Control
Virtual Path Identifier
Virtual Path Identifier
Virtual Channel Identifier
Virtual ChannelIdentifier
Payload Type Identifier
Virtual Channel Identifier
CLP
Header ErrorCheck
Payload(48 bytes)
  • Header error control
  • Detection mode
  • Protects header only (all five bytes)
  • Discards cell when header error
  • Correction mode (optional) Correct 1 bit errors
    else discard when error detected
  • Reduced cell loss in face of single bit errors
  • Reduced error detection for multiple bit errors
  • Cell delineation for SONET, SDH, etc...
  • Recalculated link-by-link because of VPI/VCI
    value changes

B
42
Why 53 Bytes?
64 5
32 4
48 5
  • Compromise reached in ITU-TS Study Group XVIII in
    June 1989

43
Queuing Delay Advantage of Small Cells
100 byte message
100 other active connections
45 Mbps
  • Delay and delay variation are small for small
    messages e.g., a digitized voice sample
  • But high header overhead

12
High overhead
Wait for other cells
10
Max
8
Just fits in one cell
Delay
6
4
(ms)
2
0
1
50
100
150
200
250
300
Payload (bytes)
A
44
Packetization Delay Advantage of Small Cells
100
10
Delay
80
8
Overhead
60
6
Overhead
Delay (ms)
40
4
20
2
0
0
0
20
40
60
80
Payload (Bytes)
45
Virtual Circuit Switching
  • Establish connection (virtual circuit) before any
    data is sent
  • Permanent Virtual Circuit (PVC), manually or
    setup signaling initiated by the network
    administrator,
  • Long lasting connections, e.g. permanent
    coonections for two IP routers
  • Switched Virtual Circuit (SVC), setup using
    signaling by one of the hosts
  • Dynamically set up on per-call basis
  • Negotiate QoS (bandwidth, delay, etc)
  • link,switch resources (bandwidth, buffers) may be
    allocated to VC to get circuit-like performance
  • Each switch on source-destination path maintains
    connection state for each passing connection
  • Incoming interface, incoming virtual circuit
    identifier (VCI), outgoing interface, outgoing
    VCI, reserved bandwidth, buffer, delay
  • Tear down
  • Forwarding each cell/packet carries VC
    identifier (not destination ID)

46
Virtual Paths and Virtual Channels
Physical Link
  • Bundles of Virtual Channels are switched via
    Virtual Paths
  • Better scalability (i.e. more capable of growing
    to large numbers of circuits)

47
ATM VCs
  • Advantages of ATM VC approach
  • QoS performance guarantee for connection mapped
    to VC (bandwidth, delay, delay jitter)
  • Drawbacks of ATM VC approach
  • Inefficient support of datagram traffic
  • one PVC between each source/dest pair) does not
    scale (N2 connections needed)
  • SVC introduces call setup latency, processing
    overhead for short lived connections

48
Switched Virtual Circuits
Signalling Channel(VPI/VCI 0/5)
Signalling Channel(VPI/VCI 0/5)
CallProcessing
ATM Switch
  • Switch and terminal exchange signalling messages
    using the predefined signalling channel, VPI/VCI
    0/5

B
49
Permanent Virtual Circuits
VPI/VCI
VPI/VCI
VPI/VCI
VPI/VCI
NetworkManagementSystem
  • Long setup time (especially with human
    intervention) means that connections are left
    active for long periods of time e.g., days, weeks
  • VPI/VCI tables setup in terminals and switches

B
50
Virtual Connections
76
Video
3
88
Voice
4
37
42
Video
Data
1
37
78
52
Data
5
Voice
Video
2
6
22
Video
Connection Table
Port VPI/VCI Port VPI/VCI 1 0/37 3 0/76
1 0/42 5 0/52 2 0/37 6 0/22 2 0/78 4 0/88
Video
Data
Video
Voice
51
Call Control Signalling
  • Call control protocol is used to establish,
    maintain, and clear virtual channel connections
    between a user and network

52
Setting Up a Call - 1
A wants to communicate with B
A
B
Setup
  • Setup message
  • Call reference
  • Called party address
  • Calling party address
  • Traffic characteristics
  • Quality of service
  • Call proceeding message
  • Call reference
  • VPI/VCI

CallProceeding
B
53
Setting Up a Call - 2
Setup
  • Internal network processing
  • Resource availability checking
  • Virtual channel or path routing
  • Function of the Network Node Interface (NNI)

CallProceeding
B
54
Setting Up a Call - 3
Setup
Setup
CallProceeding
Call Proceeding
  • Setup message
  • Call reference
  • Called party address
  • Calling party address
  • Traffic characteristics
  • Quality of service
  • VPI/VCI
  • Call Proceeding
  • Call reference
  • Called user deciding to accept call

B
55
Setting Up a Call - 4
Setup
Setup
CallProceeding
Call Proceeding
Connect
  • Connect message
  • Call reference
  • Indicates call acceptance
  • Connect Acknowledge
  • Call reference

Connect Ack
B
56
Setting Up a Call - 5
Setup
Setup
CallProceeding
Call Proceeding
Connect
Connect
Connect Ack
Connect Ack
  • Calling party informed that call is available for
    user information exchange

B
57
Bandwidth Negotiation
UNI
NNI
UNI
Setup (20 Mb/s)
Setup (15 Mb/s)
Setup (10 Mb/s)
Connect (10 Mb/s)
Connect (10 Mb/s)
Connect (10 Mb/s)
58
NNI
Cell Format
7
6
5
4
3
2
1
0
Virtual Path Identifier
Virtual Path Identifier
  • Supports 212 Virtual Paths
  • Supports virtual connection routing
  • Distribution of topology information
  • Distribution of resource availability information
  • Public version being standardized by ITU TS
  • Private version specified by ATM Forum Technical
    Working Group

Virtual Channel Identifier
Virtual Path Identifier
Virtual ChannelIdentifier
Virtual Channel Identifier
Payload Type Identifier
CLP
Header ErrorCheck
Payload(48 bytes)
CLP Cell Loss Priority
C
59
Address to End Station
Native E.164 or AESA
ATM End System Address (AESA) Format
Public ATM Network
Private ATM Switch
Private UNI
Public UNI
60
ATM Service Categories
  • Constant Bit Rate (CBR)
  • Continuous flow of data with tight bounds on
    delay and delay variation
  • Real-Time Variable Bit Rate (rt-VBR)
  • Variable bandwidth with tight bounds on delay and
    delay variation
  • Non-Real-Time Variable Bit Rate (nrt-VBR)
  • Variable bandwidth with tight bound on cell loss
  • Available Bit Rate (ABR)
  • guarantee minimum
  • Flow control on source with tight bound on cell
    loss
  • Unspecified Bit Rate (UBR)
  • No guarantees (i.e., best effort delivery)

Service Model Guarantees? Guarantees? Guarantees? Guarantees? Congestion feedback
Service Model Bandwidth Loss Order Timing Congestion feedback
CBR Constant rate yes yes yes No congestion
VBR Guaranteed rate yes yes yes No congestion
ABR Guaranteed minimum rate no yes no yes
UBR none no yes no no
61
AAL1 Adaptive Clock Method
Received Cells
Reconstructing the bit stream
Continuous Bit Stream
Speed up bit clock
Slow down bit clock
Substitute Cells
Water Mark
  • AAL1 for constant bit rate (CBR) services, e.g.
    circuit emulation
  • Bit stream rate is independent of ATM network and
    (theoretically) can be any value
  • Cell delay variation is critical to buffer sizing
    and bit clock jitter

B
62
AAL2
  • AAL2 variable bit rate (VBR) services, e.g. MPEG
    video
  • Emulation small payload to reduce packetization
    delay
  • One cell can carry data from multiple users

B
63
AAL3/4
0 - 65535
Bytes
Protocol Data Unit (PDU)
Data
Common Part Convergence Sublayer (CPCS) Protocol
Data Unit (CS-PDU)
Bytes
4
4
CPCS Header
CPCS Trailer
2
2
Bytes
44
Segmentation and Reassembly (SAR) sublayer
User Data
TYPE
LEN
MID
SEQ
CRC
AAL Trailer
2
AAL Header
  • AAL3/4 for data (e.g. IP datagrams)
  • 44 Bytes of Data per Cell
  • Type the first, last, middle or single cell
  • SEQ sequence of the cell (to detect the cell
    loss)
  • Message Identifier (MID) multiplex several PDUs
    onto a single virtual connection
  • Len length of bytes of PDU in the cell
  • CRC-10 Checking per Cell

data
D
64
AAL 5
0 - 65535
Bytes
Data
PDU
Error detection fields
2
2
4
Bytes
0-47
CS-PDU
Pad
0
Len
CRC
48
  • 48 Bytes of Data per Cell
  • Uses a paidload type identifier (PTI) bit in the
    ATM header to Indicate Last Cell
  • Only One PDU at a Time on a Virtual Connection
  • CRC-32 Per PDU CRC for error checking

0
. . .
48
1
Last cell flag
Not drawn to scale
C
65
ATM Addressing
  • Public networks
  • E.164 numbers (telephone numbers)
  • Up to 15 digits
  • Private networks
  • 20 byte address
  • Format modeled after OSI NSAP (Network Service
    Access Point)
  • Mechanisms for administration exist
  • Hierarchical structure will facilitate virtual
    connection routing in large ATM networks
  • MAC address will be encapsulated within NSAP

B
66
ATM End System Address (AESA)
AESA Format
End System- Supplied
Network-Supplied
Data Country Code (DCC)
39
HO-DSP
End System ID
DCC
SEL
SEL
International Code Designator (ICD)
47
HO-DSP
End System ID
IDC
SEL
SEL
E.164 Private Address
45
E.164 Number
End System ID
SEL
HO-DSP
Private UNI
  • Selector (Not used by Network for Routing)

Higher Order Domain- Specific Part
(HO-DSP)-routing field
67
IP over ATM
  • Classic IP
  • Layer 3 networks
  • connect LANs
  • MAC (802.3) and IP addresses
  • IP over ATM
  • Replace LAN segments with ATM network
  • ATM addresses, IP addresses

68
IP-over-ATM (Cont)
  • Packet journey in IP-over-ATM network
  • at Source Host (IP-over-ATM router)
  • IP layer maps between IP and ATM dest address
  • IP packet into ATM AAL5 PDUs
  • from IP addresses to ATM addresses just like IP
    addresses to 802.3 MAC addresses (ARP)
  • passes datagram to AAL5
  • AAL5 encapsulates data, segments cells, passes to
    ATM layer
  • ATM network moves cell along VC to destination
  • at Destination Host (IP-over-ATM router)
  • AAL5 reassembles cells into original datagram
  • if CRC OK, packet is passed to IP

69
Ethernet Switching vs. Virtual Circuit Switching
  • No connection setup (connection less)
  • Packet carries dest. addr.
  • Switching based on globally unique MAC address
  • a host does not know whether the network is
    capable of delivering the packet when it sends
    the packet
  • Each packet is forwarded independently and may be
    out of order
  • A switch and link failure might not have any
    serious effect if it is possible to find an
    alternate route
  • Establish connection state before sending any
    data (connection oriented)
  • Setup latency, processing overhead, scalability
    (capability to grow to a large network)
  • Packet/cell carries VCI
  • Switching based on incoming port VCI (unique
    per port)
  • VCI changed at the output port
  • Negotiate the QoS parameters and allocate
    resources (buffer, bandwidth) to VC
  • If no enough resource, reject the connection
    request
  • QoS performance guranteed for connection
    (bandwidth, delay, delay jitter)
  • Each cell is routed along the established
    connection in order
  • If a switch or a link fail, tear down the old
    connection and establish a new connection

Many ATM ideas adopted in IP networks called MPLS
(more later)
70
Todays Homework
  • Peterson Davie, Chap 3, 4th ed
  • -3.1
  • -3.5
  • -3.7
  • -3.8
  • -3.13
  • -3.26
  • -3.30
  • Download and browse ATM UNI4.0 spec and relate
    contents to todays lecture
About PowerShow.com