ATM Networks: An Overview

ATM Networks: Overview
q STM = Synchronous Transfer Mode,
ATM = Asynchronous Transfer Mode
Allows any-speed and even variable rate connection
Broadband = Rate greater than primary rate (1.5 Mbps)
q ATM = Short fixed size 53-byte cells
q Connection oriented Þ Virtual Channels (VC)
q Labels vs addresses
Þ Better scalability in number of nodes

o Slotted system Þ Better scalability in distance-bandwidth
o Switches vs routers
Þ Cheaper due to fixed size, short address, simplicity
o Seamless Þ Same technology for LAN, MAN, WAN
o Data, voice, video integration
o Everyone else is doing it

History of ATM
q 1980: Narrowband ISDN adopted
q Early 80's: Research on Fast Packets
q Mid 80's: B-ISDN Study Group formed
q 1986 ATM approach chosen for B-ISDN
q June 1989: 48+5 chosen (64+5 vs 32+4).
q October 1991: ATM Forum founded
q July 1992: UNI V2 released by ATM Forum
q 1993: UNI V3 and DXI V1
q 1994: B-ICI V1

Private
NNI
Private
UNI
Public
UNI
ATM Network Interfaces
Computer
Private
Switch
Public
Switch
Router
Digital
Service
Unit
DXI
B-ICI
Public
UNI
Public
NNI
Private
UNI
Private
Switch
Public
Switch
B-ICI
Public
Switch
Regional Carriers
Public
Switch
Long
Distance
Carrier
Computer
Computer

ATM Network Interfaces
q User to Network Interface (UNI):
Public UNI, Private UNI
q Network to Node Interface (NNI):
q Private NNI (P-NNI)
q Public NNI = Inter-Switching System Interface (ISSI)
Intra-LATA ISSI (Regional Bell Operating Co)
q Inter-LATA ISSI (Inter-exchange Carriers)
ÞBroadband Inter-Carrier Interface (B-ICI)
q Data Exchange Interface (DXI)
Between packet routers and ATM Digital Service Units (DSU)

Protocol Layers
ATM
Layer
ATM
Adaptation
Layer
Physical
Layer
ATM
Layer
Physical
Layer
ATM
Layer
ATM
Adaptation
Layer
Physical
Layer

Connections Vs Channels
q VP connections (VPCs) = Series of VP Links
q VC connections (VCCs) = Series of VC Links
to make an end-to-end link
q VC = VCL or VCC, VP=VPL or VPC
q Call = Multiple connections
SSwwiittcchh SSwwiittcchh End
System
End
System
End
System
End
System Switch Switch
VC
Link
VC
Link
VC
Link
VP
Link

VP/VC Assignment/Use
Switch
23 56
Video Data
37 34
Data Voice
2
1
23
3
56
4
5 65
76
6
1
1
2
2
Port
0/37
0/34
0/23
0/56
VPI/VCI
In
1/23
0/56
0/65
4/76
VPI/VCI
3
Features
q One ATM LAN can be multiple virtual LANs
q Logical subnets interconnected via routers
q Need drivers in hosts to support each LAN
q Only IEEE 802.3 and IEEE 802.5 frame formats supported
q Doesn't allow passive monitoring
q No token management (SMT), collisions, beacon frames
LE Header (2 Bytes) Standard IEEE 802.3 or 802.5 Frame
The Ohio State University Raj Jain
16
LAN Emulation
q Problem: Need new networking s/w for ATM
q Solution: Let ATM network appear as a virtual LAN
q LAN emulation implemented as a device driver below the
network layer
Bridge Bridge
ATM
Port
Out

LAN Emulation
LAN Emulation Server (LES)
ATM Switches ATM client B
Bridge
2. Clients send
messages on
the VC
1. Clients get
receipient’s
address from
LES and setup a
VC.
Broadcast/Unknown Server (BUS) Non-ATM client
4. Messages for non-
ATM clients are
forwarded through a
bridge
3. Messages for
ATM clients are
delivered directly.

Operation
q Initialization: Client gets Server's address from a
well known ATM address
q Registration: Client sends a list of its MAC
addresses to Server
q Address Resolution: Client sends ARP request to
Server
q Server, Clients, Bridges answer ARP
q Client setups a direct connection
q Broadcast/Unknown Server (BUS):
Forwards multicast traffic to all members

Token Ring/
ATM Switch
Ethernet/
ATM
Switch
LAN Emulation Configuration 1
q LAN/ATM switches provides bridging functions
ATM
Stations
Token Ring Stations
Ethernet Stations


LAN Emulation:
Summary
q LAN emulation allows current
applications to run on ATM
networks without changes
q Multiple virtual LANs on one ATM
network
q Disadvantage:
ATM is hidden from applications
Þ Can’t use new ATM services

IP Over ATM
q ATM similar to point-to-point WANs.
Simpler than LAN emulation
q IP address:123.145.134.65
ATM address:¼1-614-999-2345-¼
q Issue: IP Address Û ATM Address translation
q Address Resolution Protocol (ARP)
q Inverse ATM ARP: VC Þ IP Address
q Solution: Logical IP Subnet (LIS) Server
q Ref: RFC 1577

IP Over ATM
q ATM similar to point-to-point WANs.
Simpler than LAN emulation
q IP address:123.145.134.65
ATM address:¼1-614-999-2345-¼
q Issue: IP Address Û ATM Address translation
q Address Resolution Protocol (ARP)
q Inverse ATM ARP: VC Þ IP Address
q Solution: Logical IP Subnet (LIS) Server
q Ref: RFC 1577

IP Over ATM:
Summary
q Virtual circuits in place of real circuits
q IP to ATM address translation
Þ ARP and inverse ARP
q Clients register addresses with server
q Broadcasts are expensive
Þ Not used

Summary
q ATM Overview: History, Why and What
q Interfaces: PNNI, NNI, B-ICI, DXI
q Protocol Layers: AAL, ATM, Physical layers, Cell format
q LAN Emulation
q IP over ATM

ATM Books
q H. Dutton and Peter Lenhard, “Asynchronous Transfer
Mode (ATM) Technical Oveview,” 2nd Ed., Prentice Hall,
1995.
q R.O. Onvural, "Asynchronous Transfer Mode Networks:
Performance Issues," 2nd Ed., Artech House, 1995, 535 pp.
q W. Stallings, "ISDN and Broadband ISDN with Frame
Relay and ATM," Prentice-Hall, 1995, 581 pp.
q U. Black, "ATM: Foundation for Broadband Networks,"
Prentice-Hall, 1995, 425 pp.
q M. de Prycker, "Asynchronous Transfer Mode," 3nd
Edition, Prentice Hall, New York, 1995, 380 pp.
q B. C. Lindberg, "Digital Broadband Networks and
Services," McGraw-Hill, 1994, 248 pp.
q H. Saito, "Teletraffic Technologies in ATM Networks,"
Artech House, Norwood, MA, 1993, 176 pp.
q Y. Viniotis and R.O. Onvural, Ed., "Asynchronous Transfer
Mode," Proceedings of TRICOMM'93, Plenum Press, New
York, April 1993, 224 pp.