Emerging Technologies I (Frame Relay, ATM, V-IP)

PACKET ROUTING ISSUES • PHILOSOPHIES -- DATAGRAM: EACH PACKET INDEPENDENT • LOAD SPREAD -- VIRTUAL CIRCUIT: ALL PACKETS OF A MESSAGE USE SAME PATH • RESERVE RESOURCES & ARRIVE IN ORDER • MORE “SET UP” OVERHEAD • ROUTING -- EFFICIENT PATH & CONGESTION CONTROL -- MANY APPROACHES • ROUTING ALGORITHMS -- STATIC DIRECTORY -- DYNAMIC ROUTING -- DECENTRALIZED SCHEMES • CONGESTION CONTROL -- WANT TO AVOID “GRIDLOCK” -- APPROACHES: PERMITS, “SLOW DOWN” REQUEST, DISCARD 2 ROUTING EXAMPLE CHICAGO P1 HOST A HOST X 5 1 MESSAGE (2000 bits) MIT Dis-assembly BOSTON P1 LA P2 P1 MESSAGE (2000 bits) P2 UCLA Re-assembly Routing 3 SOURCE NODE (MESSAGE DISASSEMBLED INTO PACKETS) P2 NEW YORK 3 4 P2 DENVER DESTINATION NODE (REASSEMBLE MESSAGE FROM PACKETS) ADVANTAGES: - NOT TIE UP COMMUNICATION LINES FOR LONG PERIODS (I.E., NO LONG MESSAGES) -- INTERLEAVE PACKETS - ON COMMUNICATION ERROR, ONLY NEED TO RETRANSMIT PACKET AFFECTED RATHER THAN ENTIRE MESSAGE - BUFFER MANAGEMENT SIMPLER / LESS DEADLY EMBRACE - ABLE TO SHIP PACKETS IN PARALLEL (PARALLEL PROCESS) -ABLE TO SEND PARTIAL MESSAGE (PACKET) WITHOUT WAITING TO RECEIVE ENTIRE MESSAGE (PIPELINE PRO CESS) THE COLLAPSE (IMPLOSION) OF “POTS” • AT&T LONG-DISTANCE NETWORK – HANDLES 125M CALLS/DAY – AVERAGE CALL = 5 MINUTES – EACH CALL USES 64K bps – TOTAL = 28.8G bps (AVERAGED) – MUCH LESS THAN CAPACITY OF SINGLE OPTICAL FIBER ! • EVEN IF TOTAL POPULATION TALKED 24 HR/DAY – TOTAL = 12.8T bps • TREMENDOUS EXCESS CAPACITY – “DARK FIBER” • WHY DOESN’T / HASN’T “POTS” COLLAPSED? QUALITY OF SERVICE (QoS) TRADEOFFS / REQUIREMENTS • INTERNET GIVES “BEST EFFORT”, BUT NO GUARANTEE RELIABILITY LOW LOW HIGH DATA (INTERNET) [PACKET SWITCH] TIMELINESS VOICE (“POTS”) HIGH [CIRCUIT SWITCH] • CAN A SINGLE NETWORK SERVICE BOTH NEEDS? • OTHER DIFFERENCES (TERMINOLOGY, REGULATIONS, DEPRECIATION, RATE-OF-CHANGE) • PLUS OTHER APPLICATION NEEDS (E.G., BULK FILES, MOVIES, HDTV, ETC.) CAUSE OF DELAYS IN PACKET NETWORK INCOMING MESSAGES • • • 1 4 2 5 3 ROUTER 6 OUTGOING MESSAGES PACKET SIZE AND BACKLOG – CAN’T SEND NEXT PACKET, UNTIL CURRENT ONE SENT – MAY ALREADY BE SEVERAL WAITING TO BE SENT OVER SAME LINE ROUTER SPEED – HOW FAST DETERMINE OUTGOING LINE – OTHER FACTORS: PRIORITY, ERROR DETECTION ALTERNATE ROUTE IMPACTS – PACKETS MAY ARRIVE OUT OF ORDER – MUST WAIT FOR CORRECT SEQUENCE TO BE RE-ASSEMBLED PACKET SIZE SOLUTION (AND PROBLEM !) • • • ASYNCHRONOUS TRANSFER MODE (ATM) – ASYNCHRONOUS (E.G., PACKETS) VS. SYNCHRONOUS (E.G., TDM) STANDARDIZED 53 BYTE PACKET - - WHY 53? – 5 BYTE HEADER – 48 BYTES DATA IMPACT ON ROUTER (BASICALLY A SPECIALIZED COMPUTER) – PREVIOUS: • 1000 BYTE PACKET @ 1 M bps = 10 ms (1/100 th of sec) • FOR A 100 MIP NODE: 10 ms = 1,000,000 INSTRUCTIONS • IF ROUTING TOOK 10,000 INSTRUCTIONS = 1% ROUTER CAPACITY – NOW: • 53 BYTE PACKET @ 100 M bps = 5 µS (5 millionths of a sec) • FOR A 1000 MIP NODE, 5 µS = 5,000 INSTRUCTIONS • IF ROUTING STILL TOOK 10,000 INSTRUCTIONS = 200% OF CAPACITY ! – FUTURE: • HOW HANDLE 1G+ bps LINES? ATM PATH ROUTING STRATEGY (Virtual Circuit) • KEY CONCEPT: PRE-CALCULATE AND PRE-ALLOCATE PATH • NO SOURCE OR DESTINATION ADDRESSES USED IN CELL • MINIMAL DELAY IN PASSING CELL ON Cell 17 2 DATA 12 1 A B 32 13 C 25 5 X Y 24 Z 45 34 # Line 17 13 17 # Line 17 13 New # 63 4 # Line 3 # 63 34 Line 34 # Line # Host 17 17 New # # Line 75 75 45 45 X New # # Host 12 12 X RELATIONSHIP OF IP TO ATM • ATM ADAPTATION LAYERS (AAL5) [See Appendix for more details] FTP / HTTP Layer 1 M byte web page to be transferred ... IP Layer ATM Layer ... Divided into 1000-byte packets (9180 actual default) Each packet divided into 53-byte cells • ADDRESS MAPPING: - MUST MAP IP ADDRESS TO ATM ADDRESS AT “SETUP” • USUALLY VIA A SHARED SERVER (WITH KNOWN ATM ADDRESS) - MUST MAP EACH IP ADDRESS TO ATM FOR EACH PACKET AFTER SETUP ATM CHALLENGES / OBSTACLES • ATM HARDWARE (CURRENTLY) EXPENSIVE • MIGRATION COSTS AND COMPLEXITIES • STANDARDS BATTLES/COMPROMISES – MULTIPLE SELF-INTERESTS – E.G., ATM ADDRESS FORMAT DISPUTE (BOTH SUPPORTED) • TELEPHONE: 8-OCTET FORMAT (ISDN PHONE NUMBER) – CCITT • ATM FORUM: 20-OCTET NETWORK SERVICES ACCESS POINT (NSAP) – CISCO, IBM, etc. FUTURE OF TCP/IP (IPng, IPv6) • CURRENT IPv4 (SINCE 1970s) LIMITATIONS – IP ADDRESS = 32 BITS (MAX 4 BILLION NODES) – REAL-TIME AUDIO AND VIDEO POOR • MAINTAIN – CONNECTIONLESS DELIVERY (EACH DATAGRAM INDEPENDENT) – SENDER CHOOSES DATAGRAM SIZE (MAX = 64K BYTES) – SENDER SPECIFIES MAXIMUM HOPS • NEW (IPv6) – ADDRESS = 128 BITS (2128 = 3.4 x 1038) - WHY? – PRE-ALLOCATION OF NETWORK RESOURCES (“FLOW”) • RESERVE AND RESTRICT – MAXIMUM FRAGMENT SIZE DETERMIINED IN ADVANCE • NOT AS DYNAMIC – PROVISION FOR PROTOCOL EXTENSION – MORE FLEXIBLE HEADER FORMAT/OPTIONS – SUPPORT: UNICAST, CLUSTER, MULTICAST IPv6 ADDRESS ISSUES • FORMATS: – – – – TRADITIONAL IPv4 = 104. 230. 140. 100 IPv6 = 104. 230. 140. 100. 255. 255. 255. 255. 0. 0. 17. 128. 150. 10. 255. 255 IPv6 = 68E6: 8C64: FFFF: FFFF: 0: 1180: 96A: FFFF (HEXADECIMAL) ALSO PROVISIONS FOR ABBREVIATIONS, ESP IF SEQUENCES OF 0’s (::) • ADDRESS SPACE ALLOCATION – TRADITIONAL IPv4 - 2 PARTS: • NETWORK PREFIX (CENTRAL MANAGED) • HOST SUFFIX (ASSIGNED BY ORGANIZATION) – IPv6 OFFER VARIES POSSIBILITIES, SUCH AS: • • • • PROVIDER ID SUBSCRIBER ID SUBNET ID NODE ID (E.G., IF 48 BITS CAN = ETHERNET ADDRESS) OTHER INTERNET EMERGING TECHNOLOGIES & ISSUES • TECHNOLOGIES – SATELLITE (POINT-TO-POINT, SYNCHRONIZED) – PACKET RADIO – etc. • MULTI-MEDIA – REAL-TIME AUDIO AND VIDEO EXPERIMENTS • NEXT GENERATION INTERNET (NGI) – DARPA FUNDED – 1G bps → 1 T bps (OVER ATM) • INTERNET II (www.internet2.org -- not .com) – 170 UNIVERSITIES – 622 M bps → 2.4 G bps • OTHER EXPERIMENTS APPENDIX: ATM ADAPTION LAYERS • TYPE 1 - CONSTANT BIT RATE (CBR) - VOICE AND VIDEO • TYPE 2 - VARIABLE BIT RATE (VBR) - PACKET VIDEO • TYPE 3 - CONNECTION-ORIENTED VBR DATA TRANSFER - FILE TRANSFERS • TYPE 4 - CONNECTIONLESS VBR DATA TRANSFER - SHORT BURSTY • TYPE 5 - SIMPLE & EFFICIENT ADAPTION LAYER (SEAL/AAL5) - TYPE 3 WITHOUT ERROR DETECTION (REPLACES 3 AND 4) ATM NETWORK INTERFACES PUBLIC ATM NETWORK A PUBLIC ATM NETWORK B ATM ATM PUBLIC NNI ROUTER PRIVATE ATM NETWORK ATM ATM B-ICI ATM ATM ATM PUBLIC UNI ATM ATM PRIVATE UNI ROUTER (e.g., AT&T) ROUTER (e.g., MCI) PRIVATE NNI PRIVATE UNI ROUTER (e.g., MIT)