1. 1 ATM LAN Emulation - Courtesy of 黃能富教授 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: nfhuang@cs.nthu.edu.tw).

2. 2 ATM LAN Emulation - Courtesy of 黃能富教授 ATM LAN Emulation An Implementation Agreement Defined by the ATM Forum to Interconnect Legacy LANs with ATM Networks for Data Transport Service.

3. 3 ATM LAN Emulation - Courtesy of 黃能富教授 Interconnection Approaches v Backbone Approach (Encapsulation Bridge) v Router Approach (IP over ATM)

4. 4 ATM LAN Emulation - Courtesy of 黃能富教授 Backbone Approach v Using bridge to translate frames between ATM and Legacy LAN, keep servers on legacy LANs, no application modifications. IETF RFC 1483 or Proprietary Encapsulations. v 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 Bridge LAN Server

5. 5 ATM LAN Emulation - Courtesy of 黃能富教授 Router Approach v Using Router to translate packets between ATM and Legacy LAN q Classical IP Model -- IETF RFC 1483 and RFC 1577 q Multiprotocol Over ATM - ATM Forum v 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 Router LAN ATM Server (e.g., VoD server) Client ATM Server Client

6. 6 ATM LAN Emulation - Courtesy of 黃能富教授 What is ATM LAN Emulation ? v Based on ATM Forum UNI specification 3.0. Using AAL 5. v A service to interconnect existing "legacy" LANs with ATM. v A service to allow all existing LAN applications to run over ATM. v A service without any change on legacy LANs and end stations. v A service needs LAN emulation to be run on an end system directly connected to the ATM network  ATM bridges and ATM end systems v A service to resolve connection-oriented networks to connectionless networks. Problems to be solved:  Address Resolution  Broadcast and Multicast v A service to support multiple logical LANs within a physical ATM network v Using Available Bit Rate (ABR) service v Using PVC, SVC, or combination

7. 7 ATM LAN Emulation - Courtesy of 黃能富教授 v Run all existing LAN applications over ATM without modification, including hardware and software. v Provide bridging function between LANs and ATM network. v Utilize ATM high bandwidth and multiple direct virtual connections. v Speed up ATM deployment. Why ATM LAN Emulation ?

8. 8 ATM LAN Emulation - Courtesy of 黃能富教授 Non-Goal for LAN Emulation v Solve existing Ethernet/Token/FDDI bridging problems. v Allow a station to receive all frames on a logical LAN. v Support existing MAC-layer protocols  SMT (Station Management protocol)  Token Ring (TR) management  TR token  TR Beacon

9. 9 ATM LAN Emulation - Courtesy of 黃能富教授 LAN Emulation Service -- Backbone for Legacy LANs ATM Network Bridge LAN Server LAN Emulation

10. 10 ATM LAN Emulation - Courtesy of 黃能富教授 LAN Emulation Service -- Client Server Computing ATM Network Bridge LAN ATM Server Client LAN Emulation Client LAN Emulation ATM workstation

11. 11 ATM LAN Emulation - Courtesy of 黃能富教授 LAN Emulation Service -- Multiple Logical (Virtual) LANs ATM Network Bridge LAN ATM Server ATM Server ATM Server ATM workstations Client Logical LAN 1 2 3

12. 12 ATM LAN Emulation - Courtesy of 黃能富教授 Why ATM LAN Emulation ? v Major differences between ATM and Legacy LANs  Connection vs. connectionless  ATM does not have MAC layer  Addressing  Broadcast and multicast ATM Layer Physical PMD Transmission Convergence Sublayer Convergence Sublayer (CS) SAR AAL ATM Applications

13. 13 ATM LAN Emulation - Courtesy of 黃能富教授 LAN Emulation Protocol Stack (A Bridging Protocol) Existing Applications (e.g.,NetBios) NDIS/ODI Driver I/F MAC Layer Physical Layer Existing Applications (e.g.,NetBios) NDIS/ODI Driver IF ATM Layer Physical Layer AAL 5 LAN Emulation Emulate Ethernet/ Token Ring/FDDI MAC MAC Bridging LAN Emulation AAL 5 ATM PHY ATM PHY Ethernet/Token Ring/FDDI Legacy LAN Host ATM-LAN Bridge ATM Switch ATM Host

14. 14 ATM LAN Emulation - Courtesy of 黃能富教授 Emulated LAN Types and Formats v An Emulated LAN provides the functionality of a single LAN segment: 802.3 or 802.5, but not both. v Not emulate all the details of the emulated LAN. e.g., Ethernet collision, token, and beacon frames. v Using the same frame format for RFC 1483 VC-multiplexing/bridging format. v Client-ID is used for echo suppression. v No FCS for emulated MAC frames. LAN Emulation Header Client-ID (2 octets) 802.3 Ethernet frame  Destination MAC  Source MAC  Type/Length  Data No FCS LAN Emulation Header 802.5 frame  Frame Control  Destination MAC  Source MAC  Type/Length  Data No FCS Client-ID (2 octets)

15. 15 ATM LAN Emulation - Courtesy of 黃能富教授 LAN Emulation Components v 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 v LAN Emulation Server (LES)  Provide clients registration  Resolving MAC addresses to ATM addresses  Each emulated LAN has one LES v 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 v LE Configuration Server (LECS)  Directing LECs to the corresponding LES  Optional

16. 16 ATM LAN Emulation - Courtesy of 黃能富教授 LAN Emulation Functions v Initialization:  Client gets Server's address from a well known ATM address. v Registration:  Client sends a list of its MAC addresses to Server. v Address Resolution:  Client sends ARP request to Server.  Server, Clients, or Bridges answer the ARP.  Client setups a direct connection to the destination address. v Data forwarding:  Multicast and Broadcast traffic are forwarded to all members.

17. 17 ATM LAN Emulation - Courtesy of 黃能富教授 LAN Emulation Architecture ATM Network Bridge LAN ATM Server LAN Emulation UNI (LUNI) ATM workstation LAN Emulation Service  Initialization  Registration  Address Resolution  Data Forwarding LAN Emulation Clients

18. 18 ATM LAN Emulation - Courtesy of 黃能富教授 LES # 2  Initialization  Registration  Address Resolution LAN Emulation Architecture ATM Network Bridge LAN Client ATM workstation ATM Server LAN Emulation Clients LES # 1  Initialization  Registration  Address Resolution  Data Forwarding BUS LECS LUNI LAN Emulation Servers LNNI

19. 19 ATM LAN Emulation - Courtesy of 黃能富教授 Connection Types in LAN Emulation v 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) v 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) v Configuration direct VCC

21. 21 ATM LAN Emulation - Courtesy of 黃能富教授 Address Resolution Frames v IP_ARP frames (RFC 826, November 1982)  IP --> 48-bit MAC address v LE_ARP frames (ATM-Forum/LAN Emulation over ATM Spec.)  48-bit MAC address --> 20-byte ATM address v ATM_ARP frames (RFC 1577, January 1994)  IP --> 20-byte ATM address

22. 22 ATM LAN Emulation - Courtesy of 黃能富教授 ARP Frame Format (IP_ARP) Name Len Meaning ar$hrd 2 hardware type ar$pro 2protocol type using ATMARP (IP is 0x0800) ar$hwlen 1 hardware address length ar$prlen 1 protocol address length (IP is 4) ar$op 2operation code. ARP-req = 1, ARP-reply = 2, InARP-req = 8, InARP-reply = 9, ARP-nak = 10 ar$sha 6sender hardware address ar$spa 4sender protocol address (IP) ar$tha 6 target hardware address ar$tpa 4target protocol address (IP)

23. 23 ATM LAN Emulation - Courtesy of 黃能富教授 ARP Frame Format (LE_ARP) Name Len Meaning cntl_marker2 control frame = 0xFF00 cntl_pro 1ATM LAN Emulation protocol = 0x01 cntl_ver 1 ATM LAN Emulation protocol version = 0x01 ar_opcode2 type of request cntl_sts20x0000 in request; In response: 0-10 cntl_tranid2 transaction ID cntl_reqlecid2 lecid of le client (0x00 if unknown) ar_flags2 indication of local or remote ar_smac8 source MAC address ar_tmac8 target unicast MAC address ar_satm20 ATM address of originator of le-arp request reserved4 always 0x00 ar_tatm20 target ATM address reserved32always 0x00

24. 24 ATM LAN Emulation - Courtesy of 黃能富教授 ARP Frame Format (ATM_ARP) Name Len Meaning ar$hrd2 hardware type (0x0013) ar$pro 2protocol using ATMARP (IP is 0x0800) ar$shtl 1 type and length of source ATM number (q) ar$sstl1 type and length of source ATM subaddress (r) ar$op2operation code. ARP-req = 1, ARP-reply = 2, InARP-req = 8, InARP-reply = 9, ARP-nak = 10 ar$spln1 length of source protocol address (s) (IP is 4) ar$thtl1 type and length of target ATM number (x) ar$tstl1 type and length of target ATM subaddress (y) ar$tpln1 length of target protocol address (z) (IP is 4) ar$sha qsource ATM number (E.164 or NSAP) ar$ssa r source ATM subaddress (NSAP) ar$spa ssource protocol address ar$tha x target ATM number (E.164 or NSAP) ar$tsa y target ATM subaddress (NSAP) ar$tpa ztarget protocol address

25. 25 ATM LAN Emulation - Courtesy of 黃能富教授 Initialization v LECS Connect Phase v Configuration Phase v Join Phase v Initial Registration Phase v BUS Connect Phase LAN Emulation UNI (LUNI) ATM Emulation Clients LAN Emulation Service  Initialization  Registration  Address Resolution  Data Forwarding

26. 26 ATM LAN Emulation - Courtesy of 黃能富教授 Connect, Configuration and Join Phase v Get LECS ATM address via ILMI; using well-known address to LECS; or using well known permanent connection (VPI/VCI = 0/17) v Get LES address, LAN type, Max Frame size from LECS via Configuration direct SVC or PVC (VPI/VCI) = 0/17. v Every LAN Emulation client must be configured with an ATM address and a MAC address to itself. v LE Clients set up Control direct VCCs to LAN Emulation Server. v 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 v The LES sets up a Control distribute VCC to all proxy LECs.

27. 27 ATM LAN Emulation - Courtesy of 黃能富教授 Configuration and Join Phases Proxy LAN ATM workstation ATM Server LECs LES  LAN Type  Max Frame size  Ring # if 802.5 is used BUS LECS MACa addr ATMa addr LEC Proxy LEC Config. Direct VCC Get LES Addr Join LEC-ID Control Direct VCC Control Distribute VCC

28. 28 ATM LAN Emulation - Courtesy of 黃能富教授 Initial Registration and BUS Connect v Clients register 1st pair of ATM address and MAC address to LES. v Clients send LE_ARP via control direct VCC to LES to obtain the ATM address of the BUS. v 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.

29. 29 ATM LAN Emulation - Courtesy of 黃能富教授 Initial Registration and BUS Connect Proxy LAN 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

30. 30 ATM LAN Emulation - Courtesy of 黃能富教授 LAN Emulation Service  Initialization  Registration  Address Resolution  Data Forwarding Registration v Clients register their additional ATM addresses and MAC addresses to LES. v 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 UNI (LUNI) ATM Emulation Clients

31. 31 ATM LAN Emulation - Courtesy of 黃能富教授 Registration Proxy LAN ATM workstation ATM Server LECs LES BUS MACa ATMa MACm LEC Registration Control Direct VCCs MACb ATMb MACm MACc ATMc Multicast Send VCC Multicast Forward VCC MACa ATMa MACb ATMb MACc ATMc Proxy LEC

32. 32 ATM LAN Emulation - Courtesy of 黃能富教授 Address Resolution v Resolve the ATM address corresponding to a given destination MAC address. v Client generates an ARP request and send to LES via Control Direct VCC. v BUS forwards unicast frames to all clients before the Data Direct VCC is established. v Proxy LECs response ARP requests for known MAC addresses on their segments. v 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 LAN Emulation UNI (LUNI) ATM Emulation Clients

33. 33 ATM LAN Emulation - Courtesy of 黃能富教授 Address Resolution (ATM Station to ATM Station) Proxy LAN ATM workstation ATM Server LECs LES BUS MACa ATMa MACm LEC ARP_request (1) Control Direct VCCs MACb ATMb MACm MACc ATMc Multicast Send VCC Multicast Forward VCC ARP_response (2) Data Direct VCC (3) Data (1a) Data (2a) Proxy LANs MACa ATMa MACb ATMb MACc ATMc Proxy LEC

34. 34 ATM LAN Emulation - Courtesy of 黃能富教授 Address Resolution (ATM to Legacy LAN and Legacy LAN to Legacy LAN) Proxy LAN ATM workstation ATM Server LECs LES BUS MACa ATMa LEC ARP_request (1) Control Direct VCCs MACb ATMb MACx Multicast Send VCC Multicast Forward VCC ARP_response (4) Data (1a) Proxy LANs Proxy LEC ARP_request (2) ARP_response (3) Data (2a) Data Direct VCC (5) Control Distribute VCC Frames to MACx MACa ATMa MACb ATMb MACc ATMc Proxy LEC

35. 35 ATM LAN Emulation - Courtesy of 黃能富教授 Data Forwarding v Send unicast frames to the BUS and broadcast to all the clients before the Data direct VCC is established. (Intelligent BUS?) v 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 v The LANE clients filter out frames not destined to them. v Use direct VCC for unicast when it is established. v Frame ordering problem when switch from the Multicast forward VCC to a Data direct VCC. LAN Emulation Service  Initialization  Registration  Address Resolution  Data Forwarding LAN Emulation UNI (LUNI) ATM Emulation Clients

36. 36 ATM LAN Emulation - Courtesy of 黃能富教授 Broadcast & Multicast Frames Proxy LAN ATM workstation ATM Server LECs LES BUS MACa ATMa MACm LEC Control Direct VCCs MACb ATMb MACm MACc ATMc MACm Multicast Send VCC Multicast Forward VCC Data (1) Data (2) Proxy LANs Frame to MACm MACa ATMa MACb ATMb MACc ATMc Proxy LEC

37. 37 ATM LAN Emulation - Courtesy of 黃能富教授 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 MACa ATMa MACb ATMb MACc ATMc Proxy LEC

38. 38 ATM LAN Emulation - Courtesy of 黃能富教授 Data Clipping 1st Switch Last Switch Calling Party Called Party Call Request Connect Connect ACK Initialize VCC & SAR (Start timer) Sending data will be lost Safe to send data Ready Query (timeout) Initialize VCC & SAR Ready Ind.

39. 39 ATM LAN Emulation - Courtesy of 黃能富教授 IP Applications over ATM Emulation Network -- ES (End System) X wants to send frames to ES Y. -- ES X only knows IPy. v (1) ES X sends out an IP ARP request, looking for IPy's MAC addr. v (2) ES X sends IP ARP to the broadcast server. v (3) the broadcast server forwards the frames to the Bridge. v (4) The Bridge broadcast the frames to all ESs connected to it. v (5) ES Y sends back an IP ARP response to IPx/MACx with its MACy. v (6) Bridge sends LE_ARP to LES to find MACx's ATM addr. v (7) LES responses with ATMx (in LE_ARP response) v (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. v (9) ES X records MACy. v (10) ES X begins to use IPy and MACy to send data. v (11) LES sends LE _ARP response with MACy's ATM addr. v (12) Bridge responses with its ATM addr (LE_ ARP response). v (13) ES X knew it has a direct VCC to Bridge and uses it to send data.

40. 40 ATM LAN Emulation - Courtesy of 黃能富教授 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 12 11 8a 8 13 8a 11 12 9 10 4 4 Y IPx MACx ATMx

41. 41 ATM LAN Emulation - Courtesy of 黃能富教授 LAN Emulation vs. ATM API v In order to use the power of ATM, new applications should use ATM Forum SAA ATM API to interface directly with ATM layers. v A logical "subnet" is either an Emulated LAN or an ATM API subnet. v Logical subnets are interconnected via brouters. v ATM adapter card needs to support the relevant type of logical subnet. New Applications ATM API Physical Layer Existing Applications (e.g.,NetBios) NDIS/ODI Driver IF ATM Layer Physical Layer AAL 5 LAN Emulation ATM Layer AAL1,2,3/4, 5

42. 42 ATM LAN Emulation - Courtesy of 黃能富教授 LAN Emulation Summary v LAN Emulation allows all existing legacy LAN applications run over ATM. v LAN Emulation can carry IP applications but IETF IP over ATM may not be able to carry all different LAN applications. v LAN Emulation is first major ATM application and its success is very crucial for ATM's success. v To exploit the power of ATM, new applications should use ATM API rather than LAN Emulation. v Broadcast storm of LAN Emulation on ATM WAN is a potential problem. v LAN Emulation may overlay with multiprotocol routing over ATM.