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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]). Courtesy of 黃能富教授 ATM LAN Emulation - 1 ATM LAN Emulation An Implementation Agreement Defined by the ATM Forum to Interconnect Legacy LANs with ATM Networks for Data Transport Service. Courtesy of 黃能富教授 ATM LAN Emulation - 2 Interconnection Approaches Backbone Approach (Encapsulation Bridge) Router Approach (IP over ATM) Courtesy of 黃能富教授 ATM LAN Emulation - 3 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 Courtesy of 黃能富教授 ATM LAN Emulation - 4 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) Courtesy of 黃能富教授 ATM LAN Emulation - 5 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 Courtesy of 黃能富教授 ATM LAN Emulation - 6 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. Courtesy of 黃能富教授 ATM LAN Emulation - 7 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 Courtesy of 黃能富教授 ATM LAN Emulation - 8 LAN Emulation Service -Backbone for Legacy LANs Server LAN Bridge ATM Network Bridge LAN LAN Emulation Courtesy of 黃能富教授 ATM LAN Emulation - 9 LAN Emulation Service -Client Server Computing ATM workstation LAN Emulation ATM Network ATM Server LAN Emulation Courtesy of 黃能富教授 Bridge LAN Client Client ATM LAN Emulation - 10 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 Courtesy of 黃能富教授 2 ATM LAN Emulation - 3 11 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 Courtesy of 黃能富教授 ATM LAN Emulation - 12 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 Courtesy of 黃能富教授 ATM LAN Emulation - 13 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 Courtesy of 黃能富教授 ATM LAN Emulation - 14 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 Courtesy of 黃能富教授 ATM LAN Emulation - 15 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. Courtesy of 黃能富教授 ATM LAN Emulation - 16 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) Courtesy of 黃能富教授 ATM LAN Emulation - 17 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 Courtesy of 黃能富教授 Data Forwarding ATM LAN Emulation - 18 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 Courtesy of 黃能富教授 ATM LAN Emulation - 19 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 Courtesy of 黃能富教授 ATM LAN Emulation - 21 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$tpa 6 4 6 4 Meaning hardware type protocol type using ATMARP (IP is 0x0800) hardware address length protocol address length (IP is 4) operation code. ARP-req = 1, ARP-reply = 2, InARP-req = 8, InARP-reply = 9, ARP-nak = 10 sender hardware address sender protocol address (IP) target hardware address target protocol address (IP) Courtesy of 黃能富教授 ATM LAN Emulation - 22 ARP Frame Format (LE_ARP) Name cntl_marker cntl_pro cntl_ver ar_opcode cntl_sts cntl_tranid cntl_reqlecid ar_flags ar_smac ar_tmac ar_satm reserved ar_tatm reserved Len 2 1 1 2 2 2 2 2 8 8 20 4 20 32 Meaning control frame = 0xFF00 ATM LAN Emulation protocol = 0x01 ATM LAN Emulation protocol version = 0x01 type of request 0x0000 in request; In response: 0-10 transaction ID lecid of le client (0x00 if unknown) indication of local or remote source MAC address target unicast MAC address ATM address of originator of le-arp request always 0x00 target ATM address always 0x00 Courtesy of 黃能富教授 ATM LAN Emulation - 23 ARP Frame Format (ATM_ARP) Name Len ar$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 Courtesy of 黃能富教授 ATM LAN Emulation - 24 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) Courtesy of 黃能富教授 ATM LAN Emulation - 25 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. Courtesy of 黃能富教授 ATM LAN Emulation - 26 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 Courtesy of 黃能富教授 ATM LAN Emulation - 27 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. Courtesy of 黃能富教授 ATM LAN Emulation - 28 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 Courtesy of 黃能富教授 ATM LAN Emulation - 29 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) Courtesy of 黃能富教授 ATM LAN Emulation - 30 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 Courtesy of 黃能富教授 ATM LAN Emulation - 31 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) Courtesy of 黃能富教授 ATM LAN Emulation - 32 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 Courtesy of 黃能富教授 ATM LAN Emulation - 33 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 Courtesy of 黃能富教授 ATM LAN Emulation - 34 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) Courtesy of 黃能富教授 ATM LAN Emulation - 35 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 Courtesy of 黃能富教授 ATM LAN Emulation - 36 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 Courtesy of 黃能富教授 ATM LAN Emulation - 37 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. Courtesy of 黃能富教授 ATM LAN Emulation - 38 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. Courtesy of 黃能富教授 ATM LAN Emulation - 39 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 Courtesy of 黃能富教授 ATM LAN Emulation - 40 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 Courtesy of 黃能富教授 ATM LAN Emulation - 41 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 - 42