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Introduction to Advanced Communications: Modern Carrier Networks and ATM

This course provides an overview of modern carrier networks, including how telecommunications companies organize their IP networks. Topics covered include Asynchronous Transfer Mode (ATM), which is vital for managing various types of traffic such as voice, video, and data over a single network. The course involves lectures, assignments, and assessments focusing on advanced networking techniques. Key instructors will guide students through the complexities of modern networking technologies like DSL, MPLS, and VoIP, emphasizing their importance in delivering multi-play services.

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Introduction to Advanced Communications: Modern Carrier Networks and ATM

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  1. COMP514 – Advanced Communications Lecture 1: Introduction, ATM Matthew Luckie mluckie@cs.waikato.ac.nz

  2. Introduction to Course • This is a course on modern Carrier Networks • i.e., how a telco might organise its IP network from the customer to the core. • ATM, SDH, DSL, DSLAM, BRAS, Wifi, PPP, DHCP, QoS, RADIUS, RED, GRE, L2TP, Ethernet, VLAN, BFD, VoIP, Multiplay, MPLS, LDP, RSVP, BGP

  3. Introduction to Course • Lectures • Tues 2-3 G.1.15 • Thurs 2-3 G.1.15 • Required Textbook • Broadband Network Architectures: Designing and Deploying Triple-Play Services • Chris Hellberg, Dylan Greene, Truman Boyes • Prentice Hall, 2007

  4. Introduction to Course • Lecturers • Donald Neal • Erin Gamble • Matthew Luckie • mluckie@cs.waikato.ac.nz • G.1.28

  5. Introduction to Course • Assessment • Two assignments • 15% each, 30% of final grade • Assignment 1: RADIUS. Due Fri, 7 Sept, 5pm • Assignment 2: MPLS. Due Fri, 12 Oct, 5pm • Mid-semester test • 20% • In class, Thurs 16 Aug, 2pm. • Final test • 50% • Date to be advised

  6. Introduction to Course • Volunteer for Class Rep?

  7. Modern carrier networks: motivation • In the beginning, a Telco provided an analog phone service • Cable networks provided television service over different set of cables • Then, Telco's started providing digital networking over different set of equipment

  8. Modern carrier networks: motivation • It would be nice if a different transmission network wasn’t required for each service • However, not all traffic is equal • Cable TV, Voice: real-time • Data: more tolerant of delay

  9. Modern carrier networks • Multiple ways to solve this problem • Have multiple networks • Asynchronous Transfer Mode (ATM) • MPLS • This lecture looks at the ATM solution • Cell networking

  10. Cell networking: motivation Small Packet Caught Behind Big Packet Source: Craig Partridge, Gigabit Networking, Figure 3.2

  11. Cell networking: motivation Serialisation with Cells Source: Craig Partridge, Gigabit Networking, Figure 3.3

  12. Cell networking packet cells reassembled packet Cells and Packets Source: Craig Partridge, Gigabit Networking, Figure 3.1

  13. ATM Networks • Organised in a hierarchy • Connection-oriented • Extremely low error-rate medium • Support low-cost attachments • Developed in early 1990s

  14. header data ATM Cell Format • 53 bytes: 5 byte header, 48 byte data • 48 bytes is a poor compromise • Compromise between 64-byte payload and 32-byte payload • Too large for voice, too small for data • Partially-filled cells == unproductive work

  15. ATM Hierarchy • ATM networks are designed to be interconnected • Customer/Provider: • User-Network Interface (UNI) • Protects telco’s ATM network from misbehaving customer equipment • Provider/Provider • Network-Network Interface (NNI) • Providers trust each other to be well behaved

  16. ATM Header: NNI 8 7 6 5 4 3 2 1 Virtual Path Identifier (VPI) Virtual Channel Identifier (VCI) Payload Type CLP CRC

  17. ATM Header: NNI 8 7 6 5 4 3 2 1 • VPI + VCI uniquelyidentify an ATMconnection • Two level routinghierarchy • A backbone ATMswitch routes on VPI Virtual Path Identifier (VPI) Virtual Channel Identifier (VCI) Payload Type CLP CRC

  18. ATM Header: NNI 8 7 6 5 4 3 2 1 • 3 bits of payload type • Distinguishes betweenoperations traffic anduser traffic • If the first bit is not set,the packet is user-traffic Virtual Path Identifier (VPI) Virtual Channel Identifier (VCI) Payload Type CLP CRC

  19. ATM Header: NNI 8 7 6 5 4 3 2 1 • CLP: Cell Loss Priority • Single bit • If ATM switch iscongested and has todrop packets, it shouldfirst drop packets withthis bit set Virtual Path Identifier (VPI) Virtual Channel Identifier (VCI) Payload Type CLP CRC

  20. ATM Header: NNI 8 7 6 5 4 3 2 1 • CRC: 1 byte CRCcomputed over the5 byte header Virtual Path Identifier (VPI) Virtual Channel Identifier (VCI) Payload Type CLP CRC

  21. ATM Adaptation Layer (AAL) • The ATM committee decided there was a need to define the way a packet was divided into cells • AAL 1: constant bit rate applications • AAL 2: variable bit rate applications • AAL 3: connection-oriented data applications • AAL 4: connection-less data applications

  22. AAL 3/4 Header (16 bits) Trailer (16 bits) Seq No T Data (44 bytes) Length CRC MID Type (T) values:10: Beginning of Message 00: Continuation of Message 01: End of Message 11: Single Segment Message AAL 3/4 SAR Format Source: Craig Partridge, Gigabit Networking, Figure 4.7

  23. AAL 5 • Developed by computing industry • Goal was for a more efficient AAL for data communications

  24. AAL 5 1-bit end of datagram field in ATM header header Data (48 bytes) 8-byte trailer Data + Pad (40 bytes) UU Length CRC-32 CPI AAL 5 SAR and Convergence Formats Source: Craig Partridge, Gigabit Networking, Figure 4.9

  25. Conclusion • Main contribution of cell networking is to prevent the medium being blocked by a large packet • Not as important as it once was • 1500 byte packet at 10Mbps = 1.2ms • 1500 byte packet at 10Gbps = 1.2us • QoS based on VPI/VCI still interesting

  26. Homework • Read chapter 4 of ‘Gigabit Networking’ by Craig Partridge

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