Download ATM LAN Emulation

ATM LAN Emulation

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or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise,
without prior written permission of Professor Nen-Fu Huang (E-mail: [email protected]).
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ATM LAN Emulation -
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ATM LAN Emulation
An Implementation Agreement Defined by the ATM
Forum to Interconnect Legacy LANs with ATM
Networks for Data Transport Service.
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ATM LAN Emulation -
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Interconnection Approaches
Backbone Approach (Encapsulation Bridge)
 Router Approach (IP over ATM)

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ATM LAN Emulation -
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Backbone Approach


Using bridge to translate frames between ATM and Legacy LAN, keep
servers on legacy LANs, no application modifications. IETF RFC 1483 or
Proprietary Encapsulations.
Problems to be solved
 Can not utilize ATM high bandwidth for the servers
 Address resolution (Using PVCs)
 Broadcast and multicast (Using fully connected point-to-multipoint VCCs)
LAN
Bridge
ATM Network
Bridge
LAN
Server
Server
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Router Approach

Using Router to translate packets between ATM and Legacy LAN



Classical IP Model -- IETF RFC 1483 and RFC 1577
Multiprotocol Over ATM - ATM Forum
Problems to be solved
 Applications do not have network layer (NetBios)
 Many applications on ATM servers need modification (applications expect MAC layer
underneath)
 Address resolution (IP to ATM ARP Server)
 Broadcast and multicast
ATM Network
ATM
Server
Client
Router
LAN
Client
ATM Server (e.g., VoD server)
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ATM LAN Emulation -
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What is ATM LAN Emulation ?





Based on ATM Forum UNI specification 3.0. Using AAL 5.
A service to interconnect existing "legacy" LANs with ATM.
A service to allow all existing LAN applications to run over ATM.
A service without any change on legacy LANs and end stations.
A service needs LAN emulation to be run on an end system directly connected to
the ATM network
 ATM bridges and ATM end systems

A service to resolve connection-oriented networks to connectionless networks.
Problems to be solved:
 Address Resolution
 Broadcast and Multicast



A service to support multiple logical LANs within a physical ATM network
Using Available Bit Rate (ABR) service
Using PVC, SVC, or combination
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ATM LAN Emulation -
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Why ATM LAN Emulation ?




Run all existing LAN applications over ATM without modification,
including hardware and software.
Provide bridging function between LANs and ATM network.
Utilize ATM high bandwidth and multiple direct virtual connections.
Speed up ATM deployment.
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ATM LAN Emulation -
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Non-Goal for LAN Emulation
Solve existing Ethernet/Token/FDDI bridging
problems.
 Allow a station to receive all frames on a logical
LAN.
 Support existing MAC-layer protocols

 SMT (Station Management protocol)
 Token Ring (TR) management
 TR token
 TR Beacon
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LAN Emulation Service -Backbone for Legacy LANs
Server
LAN
Bridge
ATM Network
Bridge
LAN
LAN Emulation
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LAN Emulation Service -Client Server Computing
ATM workstation
LAN Emulation
ATM Network
ATM Server
LAN Emulation
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Bridge
LAN
Client
Client
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LAN Emulation Service -Multiple Logical (Virtual) LANs
Client
ATM
Server
LAN
Bridge
Logical LAN
Logical LAN
ATM
Server
ATM Network
Bridge
Client
LAN
1
Client
Client
ATM
Server
ATM workstations
Logical LAN
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ATM LAN Emulation -
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Why ATM LAN Emulation ?

Major differences between ATM
and Legacy LANs
 Connection vs. connectionless
 ATM does not have MAC layer
ATM Applications
Convergence
Sublayer (CS)
AAL
SAR
 Addressing
 Broadcast and multicast
ATM Layer
Physical
Transmission
Convergence
Sublayer
PMD
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LAN Emulation Protocol Stack
(A Bridging Protocol)
Ethernet/Token Ring/FDDI
Legacy LAN Host
Existing
Applications
(e.g.,NetBios)
ATM Host
ATM-LAN
Bridge
ATM Switch
NDIS/ODI Driver I/F
NDIS/ODI Driver IF
Bridging
MAC
Layer
Physical Layer
Existing
Applications
(e.g.,NetBios)
MAC
PHY
LAN Emulation
LAN
Emulation
Emulate Ethernet/
Token Ring/FDDI MAC
AAL 5
ATM
AAL 5
ATM
ATM Layer
PHY
PHY PHY
Physical Layer
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Emulated LAN Types and Formats





An Emulated LAN provides the functionality of a single LAN segment: 802.3 or
802.5, but not both.
Not emulate all the details of the emulated LAN. e.g., Ethernet collision, token, and
beacon frames.
Using the same frame format for RFC 1483 VC-multiplexing/bridging format.
Client-ID is used for echo suppression.
No FCS for emulated MAC frames.
LAN Emulation Header
LAN Emulation Header
802.3 Ethernet frame
 Destination MAC
 Source MAC
 Type/Length
 Data
802.5 frame
 Frame Control
Destination MAC
 Source MAC
 Type/Length
 Data
Client-ID (2 octets)
No FCS
Client-ID (2 octets)
No FCS
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LAN Emulation Components

LAN Emulation Client (LEC)
 Provide a MAC level emulated 802.3 or 802.5 service interface
 Each client has a LAN MAC address and an ATM MAC address

LAN Emulation Server (LES)
 Provide clients registration
 Resolving MAC addresses to ATM addresses
 Each emulated LAN has one LES

Broadcast and Unknown Server (BUS)
 Send the broadcast MAC frames
 Send all multicast MAC frames
 Send unicast frames (before data direct VCC is established)
 Each emulated LAN has at least one BUS

LE Configuration Server (LECS)
 Directing LECs to the corresponding LES
 Optional
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LAN Emulation Functions

Initialization:
 Client gets Server's address from a well known ATM address.

Registration:
 Client sends a list of its MAC addresses to Server.

Address Resolution:
 Client sends ARP request to Server.
 Server, Clients, or Bridges answer the ARP.
 Client setups a direct connection to the destination address.

Data forwarding:
 Multicast and Broadcast traffic are forwarded to all members.
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ATM LAN Emulation -
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LAN Emulation Architecture
LAN Emulation Clients
ATM Server
LAN Emulation Service
 Initialization
 Registration
 Address Resolution
 Data Forwarding
ATM workstation
ATM Network
Bridge
LAN
LAN Emulation UNI (LUNI)
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LAN Emulation Architecture
LAN Emulation Clients
LAN Emulation Servers
ATM Server
LNNI
LECS
LES # 2
 Initialization
 Registration
 Address Resolution
LES # 1
LAN
 Initialization
 Registration
 Address Resolution
ATM Network
Bridge
BUS
LUNI
Client
ATM workstation
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 Data Forwarding
ATM LAN Emulation -
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Connection Types in LAN Emulation

Control Connections (LE-ARP & control frames)
 Control direct VCC (Bidirectional Point-to-point VCC between
LEC and LES).
 Control distribute VCC (Unidirectional Point-to-Multipoint VCC
from LES to LECs, optional)

Data Connections (LECs-LECs and LECs-BUS)
 Data direct VCC (Bidirectional Point-to-point VCC between
LECs).
 Multicast send VCC (Unidirectional Point-to-point VCC from
LEC to BUS)
 Multicast forward VCC (Unidirectional Point-to-Multipoint VCC
from BUS to LEC)

Configuration direct VCC
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ATM LAN Emulation -
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Address Resolution Frames

IP_ARP frames (RFC 826, November 1982)
 IP --> 48-bit MAC address

LE_ARP frames (ATM-Forum/LAN Emulation over
ATM Spec.)
 48-bit MAC address --> 20-byte ATM address

ATM_ARP frames (RFC 1577, January 1994)
 IP --> 20-byte ATM address
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ARP Frame Format (IP_ARP)
Name
Len
ar$hrd
ar$pro
ar$hwlen
ar$prlen
ar$op
2
2
1
1
2
ar$sha
ar$spa
ar$tha
ar$tpa
6
4
6
4
Meaning
hardware type
protocol type using ATMARP (IP is 0x0800)
hardware address length
protocol address length (IP is 4)
operation code. ARP-req = 1, ARP-reply = 2,
InARP-req = 8, InARP-reply = 9, ARP-nak = 10
sender hardware address
sender protocol address (IP)
target hardware address
target protocol address (IP)
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ARP Frame Format (LE_ARP)
Name
cntl_marker
cntl_pro
cntl_ver
ar_opcode
cntl_sts
cntl_tranid
cntl_reqlecid
ar_flags
ar_smac
ar_tmac
ar_satm
reserved
ar_tatm
reserved
Len
2
1
1
2
2
2
2
2
8
8
20
4
20
32
Meaning
control frame = 0xFF00
ATM LAN Emulation protocol = 0x01
ATM LAN Emulation protocol version = 0x01
type of request
0x0000 in request; In response: 0-10
transaction ID
lecid of le client (0x00 if unknown)
indication of local or remote
source MAC address
target unicast MAC address
ATM address of originator of le-arp request
always 0x00
target ATM address
always 0x00
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ARP Frame Format (ATM_ARP)
Name Len
ar$hrd
ar$pro
ar$shtl
ar$sstl
ar$op
2
2
1
1
2
ar$spln
ar$thtl
ar$tstl
ar$tpln
ar$sha
ar$ssa
ar$spa
ar$tha
ar$tsa
ar$tpa
1
1
1
1
q
r
s
x
y
z
Meaning
hardware type (0x0013)
protocol using ATMARP (IP is 0x0800)
type and length of source ATM number (q)
type and length of source ATM subaddress (r)
operation code. ARP-req = 1, ARP-reply = 2,
InARP-req = 8, InARP-reply = 9, ARP-nak = 10
length of source protocol address (s) (IP is 4)
type and length of target ATM number (x)
type and length of target ATM subaddress (y)
length of target protocol address (z) (IP is 4)
source ATM number (E.164 or NSAP)
source ATM subaddress (NSAP)
source protocol address
target ATM number (E.164 or NSAP)
target ATM subaddress (NSAP)
target protocol address
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Initialization
LECS Connect Phase
 Configuration Phase
 Join Phase
 Initial Registration Phase
 BUS Connect Phase

LAN Emulation Service
 Initialization
 Registration
 Address Resolution
 Data Forwarding
ATM Emulation Clients
LAN Emulation UNI (LUNI)
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ATM LAN Emulation -
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Connect, Configuration and Join
Phase






Get LECS ATM address via ILMI; using well-known address to LECS;
or using well known permanent connection (VPI/VCI = 0/17)
Get LES address, LAN type, Max Frame size from LECS via
Configuration direct SVC or PVC (VPI/VCI) = 0/17.
Every LAN Emulation client must be configured with an ATM address
and a MAC address to itself.
LE Clients set up Control direct VCCs to LAN Emulation Server.
Join an emulated LAN and obtain
 LAN Emulation client-ID (LEC-ID)
 Frame size
 A token ring number if 802.5 source routing is used
The LES sets up a Control distribute VCC to all proxy LECs.
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ATM LAN Emulation -
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Configuration and Join Phases
LECs
ATM Server
Config. Direct VCC
LECS
Get LES Addr
• MACa addr
• ATMa addr
Join
LEC-ID
Join
Control Direct VCC
LEC-ID
LEC-ID
ATM workstation
LAN
 LAN Type
 Max Frame size
 Ring # if 802.5 is used
Join
Proxy
LEC
Proxy
LEC
LES
BUS
Control Distribute VCC
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ATM LAN Emulation -
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Initial Registration and BUS
Connect
Clients register 1st pair of ATM address and MAC
address to LES.
 Clients send LE_ARP via control direct VCC to LES
to obtain the ATM address of the BUS.
 Clients set up a Multicast send VCC to the Broadcast
and Unknown Server (BUS). The BUS sets up a
point-to-multipoint Multicast forward VCC to all
the LE Clients.

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ATM LAN Emulation -
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Initial Registration and BUS
Connect
MACa ATMa
MACb ATMb
MACc ATMc Proxy LEC
LECs
ATM Server
• MACa
• ATMa
• MACm
Join-initial registration
LES
Control Direct VCCs
• MACb
• ATMb
• MACm
Multicast Send VCC
ATM workstation
LAN
Proxy
LEC
• MACc
• ATMc
BUS
Multicast Forward VCC
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ATM LAN Emulation -
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Registration


Clients register their additional ATM addresses and MAC addresses to
LES.
Bridges may or may not need to register all "legacy" LAN MAC
addresses behind them. If it joins the LANE with Proxy flag set, they
may not register all the MACs behind them. A Control Distributed VCC
is established to them to get LE_ARP_REQUEST.
LAN Emulation Service
 Initialization
 Registration
 Address Resolution
 Data Forwarding
ATM Emulation Clients
LAN Emulation UNI (LUNI)
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ATM LAN Emulation -
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Registration
MACa ATMa
MACb ATMb
MACc ATMc Proxy LEC
LECs
ATM Server
• MACa
• ATMa
• MACm
Registration
LES
Control Direct VCCs
• MACb
• ATMb
• MACm
Multicast Send VCC
ATM workstation
LAN
Proxy
LEC
• MACc
• ATMc
BUS
Multicast Forward VCC
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ATM LAN Emulation -
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Address Resolution





Resolve the ATM address corresponding to a given destination MAC address.
Client generates an ARP request and send to LES via Control Direct VCC.
BUS forwards unicast frames to all clients before the Data Direct VCC is established.
Proxy LECs response ARP requests for known MAC addresses on their segments.
After ARP response is received, a Data Direct VCC is established between source
and destination clients.
LAN Emulation Service
 Initialization
 Registration
 Address Resolution
 Data Forwarding
ATM Emulation Clients
LAN Emulation UNI (LUNI)
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ATM LAN Emulation -
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Address Resolution
(ATM Station to ATM Station)
MACa ATMa
MACb ATMb
MACc ATMc Proxy LEC
LECs
ATM Server
ARP_request (1)
LES
ARP_response (2)
• MACa
• ATMa
• MACm
Control Direct VCCs
Data (1a)
Data Direct VCC (3)
• MACb
• ATMb
• MACm
Multicast Send VCC
ATM workstation
Data (2a)
LAN
Proxy LANs
Proxy
LEC
• MACc
• ATMc
BUS
Multicast Forward VCC
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ATM LAN Emulation -
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Address Resolution
(ATM to Legacy LAN and Legacy LAN to Legacy LAN)
Control Direct VCCs
LECs
ARP_request (1)
ATM Server
ARP_response (4)
• MACa
• ATMa
MACa ATMa
MACb ATMb
MACc ATMc Proxy LEC
ARP_response (3)
Data (1a)
Frames to MACx
LES
ARP_request (2)
Data Direct VCC (5)
Control Distribute VCC
• MACb
• ATMb
Multicast Send VCC
ATM workstation
LAN
Proxy LANs
• MACx
Proxy
LEC
Proxy
LEC
BUS
Data (2a)
Multicast Forward VCC
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ATM LAN Emulation -
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Data Forwarding


Send unicast frames to the BUS and broadcast to all the clients before
the Data direct VCC is established. (Intelligent BUS?)
Send multicast (broadcast) frames to the BUS and broadcast to all the
clients via the Multicast forward VCC.
 MAC packets must be prefixed with LECID



The LANE clients filter out frames not destined to them.
Use direct VCC for unicast when it is established.
Frame ordering problem when switch from the Multicast forward
VCC to a Data direct VCC.
LAN Emulation Service
 Initialization
 Registration
 Address Resolution
 Data Forwarding
ATM Emulation Clients
LAN Emulation UNI (LUNI)
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ATM LAN Emulation -
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Broadcast & Multicast Frames
MACa ATMa
MACb ATMb
MACc ATMc Proxy LEC
LECs
ATM Server
• MACa
• ATMa
• MACm
LES
Multicast Send VCC
Control Direct VCCs
Frame to MACm
• MACb
• ATMb
• MACm
Data (1)
ATM workstation
LAN
Proxy LANs
Proxy
LEC
• MACc
• ATMc
•MACm
Data (2)
BUS
Multicast Forward VCC
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ATM LAN Emulation -
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Frame Ordering
MACa ATMa
MACb ATMb
MACc ATMc Proxy LEC
LECs
Control Direct VCCs
ATM Server
• MACa
• ATMa
flush(1)
Frames to MACb
flush(3)
Data (1a)
Data Direct VCC (3)
Data (3)
LES
flush(4)
Data (2a)
flush(2)
• MACb
• ATMb
BUS
Multicast Forward VCC
ATM workstation
 Two
paths from MACa to MACb
 Frames can be delivered out of order
 Send flush message over old data path
 When the flush acknowledgement ie received from the receiver
(via the Control Direct VCC), switch to the new path
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ATM LAN Emulation -
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Data Clipping
Calling
Party
1st
Switch
Called
Party
Last
Switch
Call Request
Initialize VCC
& SAR
Connect
Connect ACK
(Start timer)
Sending data
will be lost
Initialize VCC
& SAR
Ready Ind.
Safe to send data
Ready Query
(timeout)
Ready Ind.
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ATM LAN Emulation -
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IP Applications over ATM Emulation Network
-- ES (End System) X wants to send frames to ES Y.
-- ES X only knows IPy.













(1) ES X sends out an IP ARP request, looking for IPy's MAC addr.
(2) ES X sends IP ARP to the broadcast server.
(3) the broadcast server forwards the frames to the Bridge.
(4) The Bridge broadcast the frames to all ESs connected to it.
(5) ES Y sends back an IP ARP response to IPx/MACx with its MACy.
(6) Bridge sends LE_ARP to LES to find MACx's ATM addr.
(7) LES responses with ATMx (in LE_ARP response)
(8) Bridge sets up a direct VCC to ES X.
 (8a) The IP ARP response from ES Y is sent to ES X via broadcast server.
(9) ES X records MACy.
(10) ES X begins to use IPy and MACy to send data.
(11) LES sends LE _ARP response with MACy's ATM addr.
(12) Bridge responses with its ATM addr (LE_ ARP response).
(13) ES X knew it has a direct VCC to Bridge and uses it to send data.
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ATM LAN Emulation -
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IP Applications over ATM Emulation Network
-- ES (End System) X wants to send frames to ES Y.
-- ES X only knows IPy.
Y
• IPy
• MACy
LES
6
11
• IPx
• MACx
• ATMx
1
9
11
12
X
4
Bridge
13
3
8a
ATM
workstation
5
7
8
10
12
• ATMb
LAN
4
8a
2
BUS
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ATM LAN Emulation -
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LAN Emulation vs. ATM API




In order to use the power of ATM, new applications should use ATM Forum
SAA ATM API to interface directly with ATM layers.
A logical "subnet" is either an Emulated LAN or an ATM API subnet.
Logical subnets are interconnected via brouters.
ATM adapter card needs to support the relevant type of logical subnet.
New
Applications
Existing
Applications
(e.g.,NetBios)
ATM API
NDIS/ODI Driver IF
LAN Emulation
AAL1,2,3/4, 5
AAL 5
ATM Layer
ATM Layer
Physical Layer
Physical Layer
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ATM LAN Emulation -
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LAN Emulation Summary






LAN Emulation allows all existing legacy LAN applications run
over ATM.
LAN Emulation can carry IP applications but IETF IP over ATM
may not be able to carry all different LAN applications.
LAN Emulation is first major ATM application and its success is
very crucial for ATM's success.
To exploit the power of ATM, new applications should use ATM
API rather than LAN Emulation.
Broadcast storm of LAN Emulation on ATM WAN is a potential
problem.
LAN Emulation may overlay with multiprotocol routing over
ATM.
Courtesy of 黃能富教授
ATM LAN Emulation -
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