1 atm lan emulation - courtesy of 黃能富教授 atm lan emulation all rights reserved. no part of...

Courtesy of 黃能富教授 1ATM LAN Emulation -

ATM LAN Emulation

All rights reserved. No part of this publication and file may be reproduced, stored in a retrieval system, 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]).


ATM LAN Emulation

An Implementation Agreement Defined by the ATM Forum to Interconnect Legacy LANs with ATM Networks for Data Transport Service.


Interconnection Approaches

Backbone Approach (Encapsulation Bridge)

Router Approach (IP over ATM)


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)

ATM Network BridgeBridge LANLAN

Server

Server


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 lay

er underneath) Address resolution (IP to ATM ARP Server) Broadcast and multicast

ATM Network Router LAN

ATM Server (e.g., VoD server)

Client ATM Server

Client


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


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.

Why ATM LAN Emulation ?


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


LAN Emulation Service --Backbone for Legacy LANs


Server

LAN Emulation


LAN Emulation Service --Client Server Computing

ATM Network Bridge LAN

ATM ServerClient

LAN Emulation

Client

LAN Emulation

ATM workstation


LAN Emulation Service --Multiple Logical (Virtual) LANs


ATM Server

ATM ServerATM

Server

ATM workstations

Client

Client

Client

Client

Logical LAN 1

Logical LAN 2

Logical LAN 3


Why ATM LAN Emulation ?

Major differences between ATM and Legacy LANs

Connection vs. connectionlessATM does not have MAC layerAddressingBroadcast and multicast

ATM Layer

Physical

PMD

TransmissionConvergence Sublayer

Convergence Sublayer (CS)

SARAAL

ATM Applications


LAN Emulation Protocol Stack (A Bridging Protocol)

ExistingApplications(e.g.,NetBios)NDIS/ODI Driver I/F

MACLayer

Physical Layer

ExistingApplications(e.g.,NetBios)NDIS/ODI Driver IF

ATM Layer

Physical Layer

AAL 5

LAN EmulationEmulate Ethernet/Token Ring/FDDI MAC

MAC

BridgingLAN

Emulation

AAL 5

ATM

PHY PHY

ATM

PHY PHY

Ethernet/Token Ring/FDDI Legacy LAN Host

ATM-LAN Bridge

ATM Switch

ATM Host


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 HeaderClient-ID (2 octets)

802.3 Ethernet frame Destination MAC Source MAC Type/Length Data

No FCS

LAN Emulation Header

802.5 frame Frame ControlDestination MAC Source MAC Type/Length Data

No FCS

Client-ID (2 octets)


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


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.


LAN Emulation Architecture

ATM NetworkBridge

LAN

ATM Server

LAN Emulation UNI (LUNI)

ATM workstation

LAN Emulation Service Initialization Registration Address Resolution Data Forwarding

LAN Emulation Clients


LES # 2 Initialization Registration Address Resolution

LAN Emulation Architecture

ATM NetworkBridgeLAN

ClientATM workstation

ATM Server

LAN Emulation Clients

LES # 1 Initialization Registration Address Resolution

Data ForwardingBUS

LECS

LUNI

LAN Emulation Servers

LNNI


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 VC

C 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


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


ARP Frame Format (IP_ARP)

Name Len Meaningar$hrd 2 hardware typear$pro 2 protocol type using ATMARP (IP is 0x0800)ar$hwlen 1 hardware address length ar$prlen 1 protocol address length (IP is 4)ar$op 2 operation code. ARP-req = 1, ARP-reply = 2, InARP-req = 8, InARP-reply = 9, ARP-nak = 10ar$sha 6 sender hardware addressar$spa 4 sender protocol address (IP)ar$tha 6 target hardware address ar$tpa 4 target protocol address (IP)


ARP Frame Format (LE_ARP)

Name Len Meaningcntl_marker 2 control frame = 0xFF00cntl_pro 1 ATM LAN Emulation protocol = 0x01cntl_ver 1 ATM LAN Emulation protocol version = 0x01ar_opcode 2 type of request cntl_sts 2 0x0000 in request; In response: 0-10cntl_tranid 2 transaction IDcntl_reqlecid 2 lecid of le client (0x00 if unknown)ar_flags 2 indication of local or remotear_smac 8 source MAC addressar_tmac 8 target unicast MAC addressar_satm 20 ATM address of originator of le-arp requestreserved 4 always 0x00ar_tatm 20 target ATM addressreserved 32 always 0x00


ARP Frame Format (ATM_ARP)

Name Len Meaningar$hrd 2 hardware type (0x0013)ar$pro 2 protocol using ATMARP (IP is 0x0800)ar$shtl 1 type and length of source ATM number (q)ar$sstl 1 type and length of source ATM subaddress (r)ar$op 2 operation code. ARP-req = 1, ARP-reply = 2, InARP-req = 8, InARP-reply = 9, ARP-nak = 10ar$spln 1 length of source protocol address (s) (IP is 4)ar$thtl 1 type and length of target ATM number (x)ar$tstl 1 type and length of target ATM subaddress (y)ar$tpln 1 length of target protocol address (z) (IP is 4)ar$sha q source ATM number (E.164 or NSAP)ar$ssa r source ATM subaddress (NSAP)ar$spa s source protocol addressar$tha x target ATM number (E.164 or NSAP)ar$tsa y target ATM subaddress (NSAP)ar$tpa z target protocol address


Initialization

LECS Connect Phase Configuration Phase Join Phase Initial Registration Phase BUS Connect Phase


ATM Emulation Clients



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.


Configuration and Join Phases

ProxyLAN

ATM workstation

ATM Server

LECs

LES LAN Type Max Frame size Ring # if 802.5 is used

BUS

LECS • MACa addr• ATMa addr

LEC

ProxyLEC

Config. Direct VCC

Get LES Addr

Join

Join

Join

LEC-ID

LEC-ID

LEC-ID

Control Direct VCC

Control Distribute VCC


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.


Initial Registration and BUS Connect

ProxyLAN

ATM workstation

ATM Server

LECs

LES

BUS

• MACa • ATMa • MACm

LEC

Join-initial registration

Control Direct VCCs

• MACb • ATMb• MACm

• MACc • ATMc

Multicast Send VCC

Multicast Forward VCC

MACa ATMa MACb ATMb MACc ATMc Proxy LEC



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.




Registration

ProxyLAN

ATM workstation

ATM Server

LECs

LES

BUS


LEC

Registration

Control Direct VCCs


• MACc • ATMc

Multicast Send VCC




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 establi

shed. Proxy LECs response ARP requests for known MAC addresses on their segment

s. After ARP response is received, a Data Direct VCC is established between sourc

e and destination clients.





Address Resolution (ATM Station to ATM Station)

ProxyLAN

ATM workstation

ATM Server

LECs

LES

BUS


LEC

ARP_request (1)

Control Direct VCCs


• MACc • ATMc

Multicast Send VCC


ARP_response (2)

Data Direct VCC (3)

Data (1a)

Data (2a)

Proxy LANs



Address Resolution(ATM to Legacy LAN and Legacy LAN to Legacy LAN)

ProxyLAN

ATM workstation

ATM Server

LECs

LES

BUS

• MACa • ATMa

LEC

ARP_request (1)

Control Direct VCCs

• MACb • ATMb

• MACx

Multicast Send VCC


ARP_response (4)

Data (1a)

Proxy LANs ProxyLEC

ARP_request (2)

ARP_response (3)

Data (2a)

Data Direct VCC (5)

Control Distribute VCC

Frames to MACx



Data Forwarding Send unicast frames to the BUS and broadcast to all the clients b

efore the Data direct VCC is established. (Intelligent BUS?) Send multicast (broadcast) frames to the BUS and broadcast to a

ll 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 forwar

d VCC to a Data direct VCC.





Broadcast & Multicast Frames

ProxyLAN

ATM workstation

ATM Server

LECs

LES

BUS


LEC

Control Direct VCCs


• MACc • ATMc•MACm

Multicast Send VCC


Data (1)

Data (2)

Proxy LANs

Frame to MACm



Frame Ordering

ATM workstation

ATM Server

LECs

LES

BUS

• MACa • ATMa

Control Direct VCCs

• MACb • ATMb Multicast Forward VCC

flush(1)

Data Direct VCC (3) Data (1a)

Data (2a)

flush(4)

flush(3)

Data (3)

flush(2)

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

Frames to MACb



Data Clipping 1stSwitch

LastSwitch

Calling Party

Called Party

Call Request

Connect

Connect ACK

Initialize VCC & SAR

(Start timer)

Sending datawill be lost

Safe to send data

Ready Query (timeout)

Initialize VCC & SAR

Ready Ind.

Ready Ind.


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.


IP Applications over ATM Emulation Network-- ES (End System) X wants to send frames to ES Y. -- ES X only knows IPy.

Bridge LAN

ATM workstation X

LES

BUS

• ATMb

• IPy• MACy

1

2

3

5

6

7

1211

8a

8 13

8a

11

12

9 10

4

4

Y

• IPx• MACx • ATMx


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.

NewApplications

ATM API

Physical Layer

ExistingApplications(e.g.,NetBios)NDIS/ODI Driver IF

ATM Layer

Physical Layer

AAL 5

LAN Emulation

ATM Layer

AAL1,2,3/4, 5


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.

1 atm lan emulation - courtesy of 黃能富教授 atm lan emulation all rights reserved. no part of...

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