HIGH SPEED NETWORKS

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PROTOCOLS FOR QoS SUPPORT

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HIGH SPEED NETWORKS

  1. 1. P13ITE05 High Speed Networks UNIT - I Dr.A.Kathirvel Professor & Head/IT - VCEW
  2. 2. UNIT - I  Frame Relay Networks  Asynchronous transfer mode  ATM protocol architecture  ATM logical connection  ATM cell and service categories – AAL   High speed LANs: Fast, Gigabit ethernet, Fiber channel Wireless LANs
  3. 3. Introduction  Packet-Switching Networks     Switching Technique Routing X.25 Frame Relay Networks    Architecture User Data Transfer Call Control 3
  4. 4. Packet-Switching Networks     Basic technology the same as in the 1970s One of the few effective technologies for long distance data communications Frame relay and ATM are variants of packetswitching Advantages: - flexibility, resource sharing, robust, responsive  Disadvantages:   Time delays in distributed network, overhead penalties Need for routing and congestion control 4
  5. 5. Circuit-Switching    Long-haul telecom network designed for voice Network resources dedicated to one call Shortcomings when used for data:   Inefficient (high idle time)‫‏‬ Constant data rate 5
  6. 6. Packet-Switching     Data transmitted in short blocks, or packets Packet length < 1000 octets Each packet contains user data plus control info (routing)‫‏‬ Store and forward 6
  7. 7. Figure 4.1 The Use of Packets Chapter 4 Frame Relay 7
  8. 8. Figure 4.2 Packet Switching: Datagram Approach Chapter 4 Frame Relay 8
  9. 9. Advantages over Circuit-Switching    Greater line efficiency (many packets can go over shared link)‫‏‬ Data rate conversions Non-blocking under heavy traffic (but increased delays)‫‏‬ 9
  10. 10. Disadvantages relative to Circuit-Switching     Packets incur additional delay with every node they pass through Jitter: variation in packet delay Data overhead in every packet for routing information, etc Processing overhead for every packet at every node traversed 10
  11. 11. Figure 4.3 Simple Switching Network Chapter 4 Frame Relay 11
  12. 12. Switching Technique    Large messages broken up into smaller packets Datagram  Each packet sent independently of the others  No call setup  More reliable (can route around failed nodes or congestion)‫‏‬ Virtual circuit  Fixed route established before any packets sent  No need for routing decision for each packet at each node 12
  13. 13. Figure 4.4 Packet Switching: VirtualCircuit Approach Chapter 4 Frame Relay 13
  14. 14. Routing    Adaptive routing Node/trunk failure Congestion 14
  15. 15. X.25     3 levels Physical level (X.21)‫‏‬ Link level (LAPB, a subset of HDLC)‫‏‬ Packet level (provides virtual circuit service)‫‏‬ 15
  16. 16. Figure 4.5 The Use of Virtual Circuits Chapter 4 Frame Relay 16
  17. 17. Figure 4.6 User Data and X.25 Protocol Control Information Chapter 4 Frame Relay 17
  18. 18. Frame Relay Networks      Designed to eliminate much of the overhead in X.25 Call control signaling on separate logical connection from user data Multiplexing/switching of logical connections at layer 2 (not layer 3)‫‏‬ No hop-by-hop flow control and error control Throughput an order of magnitude higher than X.25 18
  19. 19. Figure 4.7 Comparison of X.25 and Frame Relay Protocol Stacks Chapter 4 Frame Relay 19
  20. 20. Figure 4.8 Virtual Circuits and Frame Relay Virtual Connections Chapter 4 Frame Relay 20
  21. 21. Frame Relay Architecture     X.25 has 3 layers: physical, link, network Frame Relay has 2 layers: physical and data link (or LAPF)‫‏‬ LAPF core: minimal data link control  Preservation of order for frames  Small probability of frame loss LAPF control: additional data link or network layer end-to-end functions 21
  22. 22. LAPF Core      Frame delimiting, alignment and transparency Frame multiplexing/demultiplexing Inspection of frame for length constraints Detection of transmission errors Congestion control 22
  23. 23. LAPF-core Formats 23
  24. 24. User Data Transfer   No control field, which is normally used for:  Identify frame type (data or control)‫‏‬  Sequence numbers Implication:  Connection setup/teardown carried on separate channel  Cannot do flow and error control 24
  25. 25. Frame Relay Call Control   Frame Relay Call Control Data transfer involves:    Establish logical connection and DLCI Exchange data frames Release logical connection 25
  26. 26. Frame Relay Call Control 4 message types needed  SETUP  CONNECT  RELEASE  RELEASE COMPLETE 26
  27. 27. ATM Protocol Architecture    Fixed-size packets called cells Streamlined: minimal error and flow control 2 protocol layers relate to ATM functions:    Common layer providing packet transfers Service dependent ATM adaptation layer (AAL)‫‏‬ AAL maps other protocols to ATM 27
  28. 28. Protocol Model has 3 planes    User Control management 28
  29. 29. 29
  30. 30. Logical Connections   VCC (Virtual Channel Connection): a logical connection analogous to virtual circuit in X.25 VPC (Virtual Path Connection): a bundle of VCCs with same endpoints 30
  31. 31. Figure 5.2 Chapter 2 Protocols and the TCP/IP Suite 31
  32. 32. Advantages of Virtual Paths     Simplified network architecture Increased network performance and reliability Reduced processing and short connection setup time Enhanced network services 32
  33. 33. 33
  34. 34. VCC Uses    Between end users Between an end user and a network entity Between 2 network entities 34
  35. 35. Figure 5.3 Chapter 2 Protocols and the TCP/IP Suite 35
  36. 36. VPC/VCC Characteristics      Quality of Service (QoS)‫‏‬ Switched and semi-permanent virtual channel connections Cell sequence integrity Traffic parameter negotiation and usage monitoring (VPC only) virtual channel identifier restriction within a VPC 36
  37. 37. Control Signaling   A mechanism to establish and release VPCs and VCCs 4 methods for VCCs:     Semi-permanent VCCs Meta-signaling channel User-to-network signaling virtual channel User-to-user signaling virtual channel 37
  38. 38. Control Signaling  3 methods for VPCs  Semi-permanent  Customer controlled  Network controlled 38
  39. 39. ATM Cells      Fixed size 5-octet header 48-octet information field Small cells reduce delay for high-priority cells Fixed size facilitate switching in hardware 39
  40. 40. Header Format       Generic flow control Virtual path identifier (VPI)‫‏‬ Virtual channel identifier (VCI)‫‏‬ Payload type Cell loss priority Header error control 40
  41. 41. Figure 5.4 Chapter 2 Protocols and the TCP/IP Suite 41
  42. 42. Generic Flow Control   Control traffic flow at user-network interface (UNI) to alleviate short-term overload conditions When GFC enabled at UNI, 2 procedures used:  Uncontrolled transmission  Controlled transmission 42
  43. 43. 43
  44. 44. Header Error Control     8-bit field calculated based on remaining 32 bits of header error detection in some cases, error correction of single-bit errors in header 2 modes:  error detection  Error correction 44
  45. 45. Figure 5.5 Chapter 2 Protocols and the TCP/IP Suite 45
  46. 46. Figure 5.6 Chapter 2 Protocols and the TCP/IP Suite 46
  47. 47. Figure 5.7 Chapter 2 Protocols and the TCP/IP Suite 47
  48. 48. Service Categories  Real-time service  Constant bit rate (CBR)‫‏‬  Real-time variable bit rate (rt-VBR)‫‏‬  Non-real-time service  Non-real-time variable bit rate (nrt-VBR)‫‏‬  Available bit rate (ABR)‫‏‬  Unspecified bit rate (UBR)‫‏‬  Guaranteed frame rate (GFR)‫‏‬ 48
  49. 49. Figure 5.8 Chapter 2 Protocols and the TCP/IP Suite 49
  50. 50. ATM Adaptation Layer (ATM)‫‏‬  Support non-ATM protocols  e.g.,  PCM voice, LAPF AAL Services  Handle transmission errors  Segmentation/reassembly (SAR)‫‏‬  Handle lost and misinserted cell conditions  Flow control and timing control 50
  51. 51. Applications of AAL and ATM       Circuit emulation (e.g., T-1 synchronous TDM circuits)‫‏‬ VBR voice and video General data services IP over ATM Multiprotocol encapsulation over ATM (MPOA)‫‏‬ LAN emulation (LANE)‫‏‬ 51
  52. 52. AAL Protocols  AAL layer has 2 sublayers:  Convergence Sublayer (CS)‫‏‬  Supports specific applications using AAL  Segmentation and Reassembly Layer (SAR)‫‏‬  Packages data from CS into cells and unpacks at other end 52
  53. 53. Figure 5.9 Chapter 2 Protocols and the TCP/IP Suite 53
  54. 54. Figure 5.10 Chapter 2 Protocols and the TCP/IP Suite 54
  55. 55. AAL Type 1     Constant-bit-rate source SAR simply packs bits into cells and unpacks them at destination One-octet header contains 3-bit SC field to provide an 8-cell frame structure No CS PDU since CS sublayer primarily for clocking and synchronization 55
  56. 56. AAL Type 3/4  May be connectionless or connection oriented  May be message mode or streaming mode 56
  57. 57. 57
  58. 58. Figure 5.12 Chapter 2 Protocols and the TCP/IP Suite 58
  59. 59. AAL Type 5  Streamlined transport for connection oriented protocols  Reduce protocol processing overhead  Reduce transmission overhead  Ensure adaptability to existing transport protocols 59
  60. 60. Figure 5.13 Chapter 2 Protocols and the TCP/IP Suite 60
  61. 61. 61
  62. 62. Emergence of High-Speed LANs  2 Significant trends  Computing power of PCs continues to grow rapidly  Network computing  Examples of requirements  Centralized server farms  Power workgroups  High-speed local backbone 62
  63. 63. Classical Ethernet     Bus topology LAN 10 Mbps CSMA/CD medium access control protocol 2 problems: A transmission from any station can be received by all stations  How to regulate transmission 63
  64. 64. Solution to First Problem  Data transmitted in blocks called frames:  User data  Frame header containing unique address of destination station 64
  65. 65. Figure 6.1 Chapter 6 High-Speed LANs 65
  66. 66. CSMA/CD  Carrier Sense Multiple Access/ Carrier Detection  If the medium is idle, transmit. If the medium is busy, continue to listen until the channel is idle, then transmit immediately. If a collision is detected during transmission, immediately cease transmitting. After a collision, wait a random amount of time, then attempt to transmit again (repeat from step 1).    66
  67. 67. Figure 6.2 Chapter 6 High-Speed LANs 67
  68. 68. Figure 6.3 Chapter 6 High-Speed LANs 68
  69. 69. Medium Options at 10Mbps    <data rate> <signaling method> <max length> 10Base5  10 Mbps  50-ohm coaxial cable bus  Maximum segment length 500 meters 10Base-T  Twisted pair, maximum length 100 meters  Star topology (hub or multipoint repeater at central point)‫‏‬ 69
  70. 70. Figure 6.4 Chapter 6 High-Speed LANs 70
  71. 71. Hubs and Switches       Hub Transmission from a station received by central hub and retransmitted on all outgoing lines Only one transmission at a time Layer 2 Switch Incoming frame switched to one outgoing line Many transmissions at same time 71
  72. 72. Figure 6.5 Chapter 6 High-Speed LANs 72
  73. 73. Bridge    Frame handling done in software Analyze and forward one frame at a time Store-and-forward Layer 2 Switch    Frame handling done in hardware Multiple data paths and can handle multiple frames at a time Can do cut-through 73
  74. 74. Layer 2 Switches      Flat address space Broadcast storm Only one path between any 2 devices Solution 1: subnetworks connected by routers Solution 2: layer 3 switching, packetforwarding logic in hardware 74
  75. 75. Figure 6.6 Chapter 6 High-Speed LANs 75
  76. 76. Figure 6.7 Chapter 6 High-Speed LANs 76
  77. 77. Figure 6.8 Chapter 6 High-Speed LANs 77
  78. 78. Figure 6.9 Chapter 6 High-Speed LANs 78
  79. 79. Figure 6.10 Chapter 6 High-Speed LANs 79
  80. 80. Figure 6.11 Chapter 6 High-Speed LANs 80
  81. 81. Benefits of 10 Gbps Ethernet over ATM     No expensive, bandwidth consuming conversion between Ethernet packets and ATM cells Network is Ethernet, end to end IP plus Ethernet offers QoS and traffic policing capabilities approach that of ATM Wide variety of standard optical interfaces for 10 Gbps Ethernet 81
  82. 82. Fibre Channel  2 methods of communication with processor:  I/O channel  Network communications  Fibre channel combines both  Simplicity and speed of channel communications  Flexibility and interconnectivity of network communications 82
  83. 83. Figure 6.12 Chapter 6 High-Speed LANs 83
  84. 84. I/O channel      Hardware based, high-speed, short distance Direct point-to-point or multipoint communications link Data type qualifiers for routing payload Link-level constructs for individual I/O operations Protocol specific specifications to support e.g. SCSI 84
  85. 85. Fibre Channel Network-Oriented Facilities    Full multiplexing between multiple destinations Peer-to-peer connectivity between any pair of ports Internetworking with other connection technologies 85
  86. 86. Fibre Channel Requirements          Full duplex links with 2 fibres/link 100 Mbps – 800 Mbps Distances up to 10 km Small connectors high-capacity Greater connectivity than existing multidrop channels Broad availability Support for multiple cost/performance levels Support for multiple existing interface command sets 86
  87. 87. Figure 6.13 Chapter 6 High-Speed LANs 87
  88. 88. Fibre Channel Protocol Architecture      FC-0 Physical Media FC-1 Transmission Protocol FC-2 Framing Protocol FC-3 Common Services FC-4 Mapping 88
  89. 89. Wireless LAN Requirements           Throughput Number of nodes Connection to backbone Service area Battery power consumption Transmission robustness and security Collocated network operation License-free operation Handoff/roaming Dynamic configuration 89
  90. 90. Figure 6.14 Chapter 6 High-Speed LANs 90
  91. 91. IEEE 802.11 Services      Association Reassociation Disassociation Authentication Privacy 91
  92. 92. Figure 6.15 Chapter 6 High-Speed LANs 92
  93. 93. Figure 6.16 Chapter 6 High-Speed LANs 93
  94. 94. Questions ? 94

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