Emphasis of the course

1. Emphasis of the course • The main emphasis of the course will be • conversant with the modern day network technologies • Sufficient background in analysis of networks/protocols. • stepping stone to future research in the field of networks Introduction

2. Course contents The topics covered in this course include • Core Computer Network: • Various layers of network, LAN technologies • Various MAC protocols • Data link control protocols • Network layer, IP routing protocols • Transport layer, TCP, UDP • Scheduling algorithms • Introduction to QoS in networks • Mobile Computing • Wireless LAN and PAN (Bluetooth) • Cellular Nw Eg GSM, CDMA, GPRS • Mobile IP and Wireless TCP • Overview of Sensor Network Introduction

3. Texts/References • Computer Networks, Latest edition - Andrew Tanenbaum • Mobile Communication, Joschen Schiller • An Engineering Approach to Computer Networking, S. Keshav • Internetworking with TCP/IP Vol.-1, ed.-3, Douglas E. Comer • Unix Network Programming : Networks APIs : Sockets and XTI. Vol.-1 ed.-2, W.Richard Stevens • Unix Network Programming: Interprocess Communications. Vol.-2. ed.-2, W.Richard Stevens • Data and Computer Communications, 6th edition. - William Stallings • Various RFCs and papers will be recommended for reading. Introduction

4. Prerequisites • Familiarity with basic networking concepts is necessary • An undergraduate course in networks is desirable • but not mandatory • Familiarity with C and unix-based system is required • Background in computer algorithm is required (undergrad level computer algorithm) • Background in basic probability theory Introduction

5. Evaluation • 20% - Mid-Sem Exam • 40% - Final End-semester Exam • 20% - LPW (75% -Conti. Eval + 25% Prac Exam) • 20% -T.A.(50% -Assign + 20% Quiz + 30% Term Paper) • Attendance • Minimum attendance is absolutely required as per University rules Introduction

6. Logical View of Internet Introduction

7. Physical View of Internet Introduction

8. Perspectives • Network designers: Concerned with cost-effective design • Need to ensure that network resources are efficiently utilized and fairly allocated to different users. Introduction

9. Perspectives (contd.) • Network users: Concerned with application services • Need guarantees that each message sent will be delivered without error within a certain amount of time. Introduction

10. Perspectives (contd.) • Network providers: Concerned with system administration • Need mechanisms for security, management, fault-tolerance and accounting. Introduction

11. Connectivity Building Blocks: • nodes: general-purpose workstations, special boxes ... • links: coax cable, optical fiber... Introduction

12. Connectivity (contd.) Direct Links: • point-to-point Point-to-point network Introduction

13. Connectivity (contd.) • multiple access … multiple access network Introduction

14. Switched networks Introduction

15. Internetworks Introduction

16. Networking at Different Stages • Different technologies and protocols work at different stages of networks. • Local Area Network (LAN) • Metropolitan Area Network (MAN) • Wide Area Network (WAN) Introduction

17. LAN • Network owned by offices, enterprises • Spans a room or a building • Restricted in size • Often use a transmission technology consisting of a single cable to which all the machines are attached. • Typically runs at 10-100 Mbps range. • Examples • IEEE 802.3 ethernet • IEEE 802.5 token ring Introduction

18. MAN • Basically a bigger version of a LAN • Normally uses similar technology like LAN • Covers a group of nearby offices or a city • May be either a private or public network • Examples • IEEE 802.6 DQDB (Distributed Queue Dual Bus) • Metro Ethernet (gigabit ethernet based platform) • IEEE 802.16 wireless MAN Introduction

19. WAN • Spans a large geographical area • Often a country or a continent • Point-to-point WAN • Usually leased from a carrier network e.g. telephone company • Circuit Switched WAN • ISDN based • Packet Switched WAN • Share resources provided by the service provider • ATM, frame relay, X.25 Introduction

20. Effective resource sharing Need to share (multiplex) network resources among multiple users. Introduction

21. Common Multiplexing Strategies • Time-Division Multiplexing (TDM): • Each user periodically gets the entire bandwidth for a small burst of time. Introduction

22. Common Multiplexing Strategies (contd.) • Frequency-Division Multiplexing (FDM): • Frequency spectrum is divided among the logical channels. • Each user has exclusive access to his channel. Introduction

23. Switching Strategies • Circuit Switching: dedicated circuit; send/receive a bit stream • end-to-end path setup before actual communication. • no congestion for an established circuit connection. Introduction

24. Circuit Switching • resources are reserved • unused bandwidth on an allocated circuit is wasted. Introduction

25. Switching Strategies (contd.) • Packet Switching: store-and-forward; send/receive messages (packets) • no prior setup of end-to-end path from the source to the destination. • packets are forwarded one hop at a time. Introduction

26. Packet Switching • greater network utilization, multiplexing possible. • typically ``best-effort" service; may face congestion. Introduction

27. Addressing • Address: byte-string that identifies a node; usually unique • physical address: device level • logical address: network level • port address: process level • Special address: application level Introduction

28. Addressing (contd.) • unicast: node-specific • broadcast: all nodes on the network • multicast: some subset of nodes on the network Introduction

29. Routing • Mechanisms of forwarding messages towards the destination node based on its address • Need to learn global information Introduction

30. Network Architecture • To reduce design complexity: • Use abstractions to hide complexity; Abstraction naturally leads to layering • Can have alternative abstractions at each layer Introduction

31. Network Architecture (contd.) Introduction

32. Protocols and Services • Each protocol module/object has two different interfaces • service interface: defines operations on this protocol. Each layer provides a service to the layer Above. • peer-to-peer interface: defines messages exchanged with peer. Protocol of “conversation” between corresponding Layers in Sender and Receiver. Introduction

33. Protocols and Services (contd.) • Term ``protocol'' is also used to denote the implementation of the peer-to-peer interface. • Multiplexing and Demultiplexing. • Headers and Encapsulation. Introduction

34. TCP/IP Layers • Physical Layer: Concerned with transmitting bits over a communication channel. • Issues largely deal with electrical and procedural interface to the physical transmission medium. Introduction

35. TCP/IP Layers (contd.) • Data Link Layer: Concerned with transforming the raw physical layer into a `link' for the higher layer. • Issues largely deal with framing, error detection/correction and multiple access. Introduction

36. TCP/IP Layers (contd.) • Internet Layer: Concerned with addressing and routing of packets. • Issues largely deal with addressing, subnetting and route determination. Introduction

37. TCP/IP Layers (contd.) • Transport Layer: Concerned with end-to-end connection characteristics. • Issues largely deal with retransmissions, sequencing and congestion control. Introduction

38. TCP/IP Layers (contd.) • Application Layer: Concerned with ``application'' protocols. • Issues largely deal with providing services to users and application developers. Introduction

39. Layering Summary • Advantages of layering: • Allows a ``divide-and-conquer'' strategy for building networks. • Easier to understand and implement as compared to a monolithic approach. • If the service interface remains unchanged, implementation of a layer can be changed without affecting other layers. Introduction

40. OSI Reference Model - The ISO Model of Architecture for Open Systems Interconnection • Exists theoretically • Services Each layer provides to layer Above • ProtocolsBetween corresponding Layers in Sender and Receiver • Good Software engineering pattern. Only specification, not implementation details Application layer (7) Presentation layer (6) Session layer(5) Transport Layer (4) Network layer (3) Data Link Layer (2) Physical Layer (1) Introduction

41. Physical layer Moves bits from one end to other • Media Dependent • Copper: Coaxial/Twisted Pair; Typically upto 100 Mbps • Fibre: Single/Multi Mode; Can transmit in Gigabits/second • Satellite: Channels of 64 kbps, 128 kbps • Radio waves: Ranges from Kbps to Mbps Introduction

42. Data Link layer Controls a single physical link • Logical Link Control (LLC): • Framing (start and stop) • Error Detection • Error Correction • Optimal Use of Links (Sliding Window Protocol) • Examples: HDLC, LAP-B, LAP-D Introduction

43. Data Link layer • Medium Access Control (MAC): • Multiple Access Protocols • Channel Allocation • Contention, Reservation, Round-robin • Examples: Ethernet (IEEE 802.3), Token Ring (802.5) Introduction

44. How to share a channel with/without a Coordinator: Medium Access Control (MAC) • Scheduled Access • Time Slotted, User knows when to transmit • Random access (CSMA/CD) • Carrier Sense • POLITENESS: If you hear some one talking, wait until s/he finishes. Introduction

45. MAC • PERSISTENT: Start immediately after line becomes free. This leads to COLLISION. If channel is busy, senses the medium persistently • 1-persistent – stations waits until channel is idle and then immediately send • p-persistent – transmits with a probability p when channel is idle • NON-PERSISTENT: Wait for some (random) time when channel is busy and then transmit immediately when idle • Collision Detection • Station must listen when transmitting • Minimum transmission time needed to detect collision • Binary Exponential Backoff Introduction

46. Network Layer • Why do we need a network layer? • Can all machines in the world be Ethernet? • Other Technologies (modems, token ring) • Goals and Services: • Hide type of subnets (Ethernet, Token Ring, FDDI . ) • Hide topology of subnets • Choose good routes • Uniform addressing scheme • OSPF, BGP in Internet Introduction

47. Transport Layer • Accepts data from session layer and split it into smaller units (if needed) and pass them to network layer • Typical transport layer would provide error-free point-to-point data channel that delivers message/bytes in the order in which they were sent • However, other possible kind could be transport of isolated messages with no guarantee • It is a true end-to-end layer from source to destination (in lower layers protocols are between each machine and its immediate neighbors) Introduction

48. Session Layer • Allows users on different machines to establish sessions between them • Allows ordinary data transport (as does transport layer) and also provides enhanced services useful for some applications (e.g. checkpointing of sessions, dialog control) Introduction

49. Presentation Layer • Performs certain functions that are requested sufficiently often to warrant finding a general solution for them • Unlike lower layers, this layer is concerned with syntax and semantics of the information transmitted • Manages abstract data structures and converts from the representation inside the computer (e.g. ASCII, Unicode) to the network standard and back Introduction

50. Application Layer • Handles application specific issues/protocols • e.g. different file naming conventions, different ways of representing text lines • Various special and general purpose facilities are taken care of by application layer while two remote applications communicate with each other. Introduction