2 5 ISDN ATM Integrated Services

2. 5 ISDN & ATM • Integrated Services Digital Network (ISDN) + telephone, fax, computer, video, security + narrowband ISDN + broadband (B-ISDN) • Asynchronous Transfer Mode (ATM) + asynchronous packet switching + voice, music, images, video, data + ATM protocol layers + ATM switching + SONET University of Calgary CS 441 2. 5 1

Integrated Services Digital Networks - ISDN • The Public Switched Telephone Network + telephones in POTS become more complex supporting voice, video and data • Digital TDM Switching + digital TDM replaces analog FDM • Subscriber Loop (digitized voice, etc) + full duplex digital transmission from the user to end office switch (TDM with PCM) • Control Signaling + common channel signaling over a packet switched network embedded in the PSTN for control, routing, monitoring, AIN services University of Calgary CS 441 2. 5 2

Principles & Goals of ISDN - late 1950 s early 60 s • evolve from the existing PSTN to support voice, text, video and data => worldwide • support both switched and non-switched (dedicated line) applications • basic bandwidth unit is 64 Kb/ s ~ digitized voice • intelligence within the network - AIN services • layered protocol architecture close to OSI • enable varied physical configurations across regional and national boundaries University of Calgary CS 441 2. 5 3

The User / Customer Interface packet switched network terminal phone PBX ISDN Interface security system LAN University of Calgary ISDN CO circuit switched network other networks CS 441 2. 5 4

ISDN User Interface Standards - Architecture • B Channel - 64 kb/ s + circuit switched, packet switched, leased line digital voice, fast data, Fax, degraded video • D Channel - 16 or 64 kb/s + carries signaling information to control B channel circuit switched calls + can carry low bandwidth telemetry + low speed data, videotex, teletex, terminals • H Channel(s) 384 or 1536 or 1920 kb/ s + user info at higher rates, customed groups packaged for each user University of Calgary CS 441 2. 5 5

ISDN Channel Structures • Basic Service => residential & small offices + Rate is 192 kb/ s + composition : two B & one D + overhead • Primary Service => larger customers + T 1 rate is 1. 544 (or 2. 048 in europe) Mb/ s + composition : 23 B channels, 1 D channel (other variations supported) University of Calgary CS 441 2. 5 6

Broadband ISDN & ATM • Today vastly larger bandwidths are desired by many classes of users => >600 Mb/ s • Users also require packet switching, ie, connectionless support • May require fibre optical cables • Asynchronous Transfer Mode (ATM) developed to support packet & circuit switching, mixed voice, video, data University of Calgary CS 441 2. 5 7

B-ISDN Transmission Services • Full duplex 155. 52 Mb/ s => likely satisfy most • Asymetrical from subscriber to the network at 155 Mb/ s, and 622. 08 Mb/ s back • Full duplex 622. 08 Mb/ s => multiple video session distribution, multiple video conferences University of Calgary CS 441 2. 5 8

B-ISDN & ATM Protocol Architecture B-ISDN and higher layer protocols ATM adaptation layer (AAL) convergence sublayer (CS) and segmentation / reassembly (SAR) sublayer ATM layer physical layer = TC and PMD sublayers transmission convergence (TC) and physical medium dependant (PMD) eg SONET University of Calgary CS 441 2. 5 9

ATM Network Interfaces computer phone PBX UNI (ISDN) video LAN University of Calgary Access Control MUX De. MUX ATM Network CS 441 2. 5 10

Asynchronous Transfer Mode • vs Synchronous Transfer Mode - STM • STM ~ TDM as in current PSTN A B mainframe C ABCABCABCABC University of Calgary CS 441 2. 5 11

ATM Multiplexing A heavy transmission, B occasional, C sleeping A B mainframe C AAAAAAABAAAAABAAAA University of Calgary CS 441 2. 5 12

ATM Cells vs Frames cell = 53 bytes long 5 byte header frame F Header University of Calgary 48 bytes data = 64 - 1500 bytes long variable length data CRC F CS 441 2. 5 13

The ATM Cell Structure GFC VPI VCI VCI PT CLP HEC 48 bytes of Data University of Calgary CS 441 2. 5 14

Classes of Services (AALs) • Constant Bit Rate (CBR) Services + voice or DSn emulation, includes mechanisms for recovering source timing info, . . . • Variable Bit Rate (VBR) Real Time + raw compressed (ie bursty) real time video, . . . • Variable Bit Rate (VBR) Non-Real Time + multimedia email, . . . • Available Bit Rate (ABR) + Web browsing, . . . • Unspecified Bit Rate (UBR) + file transfers, . . . University of Calgary CS 441 2. 5 15

ATM Adaptation Layer-AAL => class of service • ATM designed so that Adaptation Layer functions are executed in the UNI - the user network interface • Two sublayers: + => CS convergence layer divides arbitrarily long packets into fixed length PDUs + => SAR segmentation reassembly divides above PDUs into 48 byte packets (cells) user data CS PDU SAR PDU University of Calgary . . . SAR PDU . . . CS PDU SAR PDU CS 441 2. 5 16

ATM Layers AAL User Data SONET University of Calgary TC Cell Cells ATM switches CS 441 2. 5 17

Physical Layers • TC => transmission convergence sublayer + generates and receives frames, packs cells into frames, computes ATM header CRC, ie HEC, and inserts in each cell, on receipt checks HEC for each cell, discards if error, bit scrambling to avoid SONET framing pattern, . . . + based on SONET or DS 3 or ? ? ? • PMD => physical medium dependant sublayer + bit transfer between two nodes, wave shapes, timing recovery, line coding, . . . + ATM independant of this layer University of Calgary CS 441 2. 5 18

Access Control & Policing • sustained information rate (SIR) = 8 Mb/s • maximum burst length of 64 kbytes tokens at 8 million per second bursty data buffered tokens < 64 K data (with virtual token) => SIR & Burst length enable sizing buffers in switches University of Calgary CS 441 2. 5 19

Virtual Paths & Virtual Circuits VC establishment: PVCs = permanent virtual channels SVCs = switched virtual channels VC 1 VC 2 VP 1 SONET Pipe VP 2 VC 3 VC 1 VC 2 VC 3 University of Calgary CS 441 2. 5 20

Virtual Circuits & Virtual Paths Virtual Path ATM Switch Virtual Circuits University of Calgary CS 441 2. 5 21

ATM Switching • an ATM switch receives a cell • reads VPI/ VCI • reads output port and new VPI/ VCI for the next link from routing table • write the new VPI/ VCI into cell • buffers cell on destination output port + above must be done in 3 microseconds at OC-3 rates (155 Mb/ s) + above must be done in 1/ 3 microsecond at OC-24 rates (1. 2 Gb/ s) University of Calgary CS 441 2. 5 22

ATM Switch Requirements • 1 gigabit/second ~= 150 million bytes / second • => 3 million cells / second => 1/ 3 usec per cell • => in one second receive 3 million cells • => 150 million bytes of buffer storage University of Calgary CS 441 2. 5 23

SONET Optical Channel Rates • OC-1 • OC-3 51. 84 Mb/ s => • OC-9 • OC-12 466. 56 Mb/ s => • OC-18 • OC-24 University of Calgary 622. 08 Mb/ s => ATM 933. 12 Mb/ s => • OC-36 • OC-48 155. 52 Mb/ s => ATM 1244. 16 Mb/ s => ATM 1866. 24 Mb/ s => 2488. 32 Mb/ s => ATM CS 441 2. 5 24

OC-3 SONET Frames = 2430 bytes at 155 Mb/ s 270 bytes 1 B 1 B 1 B nine rows transport overhead • • • 53 byte cell • • • 125 sec University of Calgary CS 441 2. 5 25

OC-N SONET Frames = N * 51. 84 Mb/ s N * 90 bytes 1 B 1 B 1 B row 1 row 2 • • • row 9 125 sec University of Calgary CS 441 2. 5 26

DS 3 Frame ~ 44 Mb/s A 1 A 2 P Z ATM Cell • • • ATM Cell 13 -14 nibble trailer ~ 690 bytes ~ 125 sec University of Calgary CS 441 2. 5 27

Cellular Radio • paging systems + one way, ~ 30 bytes + 1 Mb/s satellite can handle 240, 000/minute • cellular phones (analog but going digital) + advanced mobile phone system (AMPS) + 10 -20 km diameter cells, 0. 6 -3 watt xmitters + 832 (30 Khz) send channels in 824 -849 Mhz + 832 (30 Khz) receive channels in 869 -894 Mhz + control, paging, signaling, data channels + half each to an A carrier and to a B carrier + 21 control and 45 data channels per cell + phone scans control channels for strongest + sends 32 bit serial # & 34 bit phone # /15 min + mobile, base stations, mobile switching office University of Calgary CS 441 2. 5 28

Personal Communications Services (PCS) • cordless phone that goes anywhere in the world • microcells, 50 -100 meters in diameter, 0. 25 watt • massive infrastructure - 40, 000 cells per cellular cell • USA auction PCS 1. 7 -2. 3 Ghz spectrum $7. 7 billion • PCS in US, PCN (personal comm net) elsewhere • handoff from cell to cell as in cellular (~300 ms) • requries location independent unique addresses across world, system must keep track of locations University of Calgary CS 441 2. 5 29

Satellite Communications • geosynchronous equatorial ~36, 000 km, <=180 + C band, 3. 7 -4. 2 GHx down, 5. 9 -6. 4 GHz up + Ku band, 11. 7 -12. 2 down, 14. 0 -14. 5 up + Ka band 17. 7 -21. 7 down, 27. 5 -30. 5 up + typical sattelite ~ 12 -20 transponders + round trip transit time ~ 300 ms + VSAT is 2 trips using hub ~ 540 ms • low orbit satellite ~750 Km, - LEO + Iridium - 77 (now 66), 6 polar orbits (big atom) + voice, data, paging, fax, navigation worldwide + 1628 mobile cells, 174 full duplex channels each + L band 1. 6 GHz, 200 MHz total bandwidth + competes with PCS University of Calgary CS 441 2. 5 30