1. Chapter 3. Data Networks

2. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul Frame Relay Networks §Key Features of X.25  inband signaling  multiplexing of virtual circuits at layer 3  flow and error control at layer 2 & 3  considerable overhead  not appropriate for modern digital communication facilities which are high-quality and reliable

3. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul Frame Relay Networks (cont’d) §Key Features of FR (f 3.8) l common-channel signaling l multiplexing of logical connections at layer 2 l no hop-by-hop flow & error control  streamlined  lower delay and higher throughput up to 2 Mbps

4. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul Frame Relay Architecture §LAPF Core Protocol (f 3.9) l implemented in all end systems and network l a minimal set of data link control functions frame delimiting, alignment, and transparency frame muxing/demuxing using the addr field inspection of frame to ensure length & format detection of transmission errors congestion control functions

5. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul FR Architecture (cont’d) §LAPF Control Protocol l implemented only in end systems (optional) l provide end-to-end flow & error control §Other Characteristics l use a permanent control-oriented virtual connection l virtually no processing by intermediate network nodes => a frame in error is discarded

6. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul FR Architecture (cont’d) §User Data Transfer l no control field in the frame format (f 3.11) impossible to do flow & error control connection set-up/tear-down carried out on separate channel at a higher layer l DLCI (Data Link Connection Identifier) same as the virtual circuit number in X.25

7. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul FR Architecture (cont’d) §Frame Relay Call Control l establishment & release of a logical connection is accomplished by the exchange of messages over a connection dedicated to call control, with DLCI = 0 l message types SETUP => CONNECT or RELEASE COMPLETE RELEASE => RELEASE COMPLETE

8. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul Chapter 4. Asynchronous Transfer Mode

9. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul ATM Protocol Architecture §Characteristics l cell relay: short fixed-size packets l a streamlined protocol with minimal error & flow control l high data rates: 155.52 Mbps, 622.08 Mbps

10. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul ATM Protocol Arch. (cont’d) §ATM-related Layers (f 4.1) l ATM layer common to all services define the transmission of data in cells define the use of logical connections l AAL service-dependent support info transfer protocols not based on ATM map between higher-layer info and ATM cells

11. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul ATM Protocol Arch. (cont’d) §Protocol Planes l User plane user info transfer with flow & error control l Control plane call control and connection control functions l Management plane plane management –manage a whole system and coordinate between all planes layer management –manage resources and parameters residing in its protocol entities

12. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul ATM Logical Connections §Types of Logical Connections (f 4.2, t 4.1) l VCC (Virtual Channel Connection) the basic unit of switching cell sequence integrity is preserved within a VCC end points may be end users, network entities, or an end user and a network entity establish a VCC based on existing VPCs with sufficient available capacity & the appropriate QoS (f 4.3) switched and semipermanent VCC –switched: on-demand, by signaling –semipermanent: long-lasting, by configuration or net mngt traffic parameter negotiation & usage monitoring

13. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul ATM Logical Conn. (cont’d) §Types of Logical Connections (cont’d) l VPC (Virtual Path Connection) a bundle of VCCs having the same end points advantages of using VPCs –simplified network architecture –increased network performance and reliability –reduced processing and short connection setup time –enhanced network services

14. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul ATM Logical Conn. (cont’d) §Control Signaling l exchange of info involved in the setup & release of VPCs and VCCs l metasignaling channel permanent channel used to set up signaling VCCs

15. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul ATM Cells §ATM Cell Format (f 4.4) l 53-byte cell with 5-byte header less queueing delay, easy switching l Header format GFC: for flow control at UNI VPI/VCI: for routing PT: type of info in payload, user or net mngt data (t 4.2) CLP: indicate cell discard in case of congestion HEC: fig 4.5-6

16. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul ATM Service Categories § Real-time Services l CBR (Constant Bit Rate) simplest service fixed data rate, tight delay upper bound uncompressed audio/video info video conf., interactive audio, A/V distribution/retrieval l rt-VBR (Variable Bit Rate) tightly constrained delay and delay variation variable data rate, bursty

17. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul ATM Service Categories (cont’d) §Non-real-time Services l nrt-VBR bursty, no tight constraints on delay and delay variation improved QoS in delay and loss data transfer application with critical response-time requirements (e.g., airline reservation)

18. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul ATM Service Categories (cont’d) §Non-real-time Services (cont’d) (f 4.8) l UBR (Unspecified Bit Rate) can tolerate variable delays and some cell losses TCP-based traffic, best-effort service l ABR (Available Bit Rate) better than UBR PCR (Peak Cell Rate) & MCR (Min. Cell Rate): at least MCR unused capacity is shared in a fair and controlled fashion among all ABR sources use explicit feedback to sources LAN interconnection

19. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul ATM Adaptation Layer §AAL Services l General services provided by AAL handling of transmission errors segmentation and reassembly handling of lost and misinserted cell conditions flow control and timing control

20. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul AAL (cont’d) §AAL Protocol Layer l CS (Convergence Sublayer) functions for specific applications using AAL service dependent SSCS(Service Specific CS), CPCS (Common Part CS) in AAL 3/4, AAL 5 l SAR (Segmentation And Reassembly) sublayer pack info received from CS into cells (48 bytes) and do the other way §Service Classes (t 4.3)

21. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul AAL (cont’d) (t 4.4) §AAL Type 1 l CBR l CS clocking and synchronization l SAR SN (Sequence Number): to check cell loss or misinsertion SNP (SN Protection): SN error correction §AAL Type 2 l VBR, for analog appl. Requiring timing info

22. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul AAL (cont’d) §AAL Type 3/4 l connectionless or connection oriented connectionless –each data block is treated independently connection oriented –may define multiple SAR logical connections over a single ATM connection

23. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul AAL (cont’d) §AAL Type 3/4 (cont’d) l message mode or streaming mode message mode –transfer of frame-based data (ex. frame relay) streaming mode –transfer of low-speed continuous data with low delay requirements

24. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul AAL (cont’d) §AAL Type 3/4 (cont’d) l CPCS alert the receiver that a block of data is coming in segments and that buffer space must be allocated for that reassembly B/E tag: a number associated with a particular CPCS-PDU BASize: max. buffer size at the receiving peer entitty for reassembly AL: a filler octet to make the length of the CPCS- PDU equal to 32 bitsl

25. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul AAL (cont’d) §AAL Type 3/4 (cont’d) l SAR ST: type of SAR-PDU; SSM, COM, BOM, EOM SN: for reassembly purpose MID –an identifier associated with the set of SAR-PDUs carrying a single SAR-SDU –used when multiplexing logical connections in a VCC

26. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul AAL (cont’d) §AAL Type 5 l provide a streamlined transport facility for higher-layer protocols that are connection oriented reduce protocol processing overhead reduce transmission overhead ensure adaptability to existing transport protocols l similar to AAL 3/4 but appropriate for high- speed data communications l no multiplexing provided

27. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul Chapter 5. High-Speed LANs

28. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul Ethernet l developed by Xerox l the basis for a family of LAN standards by IEEE 802.3 committee l operate at 10Mbps over a bus topology LAN 10BASE5, 10BASE-T l use CSMA/CD MAC protocol if medium is idle, transmit if medium is busy, continue to listen until channel is idle and transmit if collision is detected, wait random time and attempt transmission again

29. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul Fast Ethernet l a low-cost, Ethernet-compatible LAN operating at 100Mbps l use IEEE 802.3 MAC protocol and frame format l 100BASE-T (f 5.5) star-wire topology, with all stations connected directly to a central point referred to as a multipoint repeater repeater detects collisions, repeats a valid signal on all output links, and transmits a jam signal in case of a collision

30. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul Fast Ethernet (cont’d) l can operate in full-duplex mode upto 200Mbps use a switched hub, no collisions l can support both 10Mbps and 100Mbps links

31. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul Gigabit Ethernet l compatible with 10BASE-T and 100BASE-T

32. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul ATM LANs § LAN Generations l 1st generation CSMA/CD and token ring LANs terminal-to-host connectivity, client-server architecture at moderate data rates l 2nd generation 100Mbps FDDI (Fiber Distributed Data Interface) backbone LANs, high-performance workstations l 3rd generation ATM LANs aggregate throughputs and real-time transport guarantee, multimedia applications

33. By Sanghyun Ahn, Dept. of Computer Science and Statistics, University of Seoul ATM LANs (cont’d) §Requirements for 3rd G. LAN l support multiple, guaranteed classes of service l provide scalable throughput l facilitate the interworking between LAN & WAN technology §ATM LAN l use ATM as a data transfer protocol somewhere within the local premises l use as gateway to ATM WAN, backbone ATM switch, workgroup ATM