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COMP 416 Internet Protocols and Software

COMP 416 Internet Protocols and Software. Instructor: Zhijun Wang Note: Projects are available online The first quiz will be given in next lecture (Oct. 15) It covers the first 4 lectures Today’s contents Underlying Technology Virtual LAN. Chapter 3. Underlying Technology.

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COMP 416 Internet Protocols and Software

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  1. COMP 416Internet Protocols and Software Instructor: Zhijun Wang Note: Projects are available online The first quiz will be given in next lecture (Oct. 15) It covers the first 4 lectures Today’s contents • Underlying Technology • Virtual LAN TCP/IP Protocol Suite

  2. Chapter 3 Underlying Technology Objectives • Understand the Ethernet • Understand the types of point-to-point WANs • Understand the types of switched WANs • Differentiate between repeaters, bridges, routers, and hubs TCP/IP Protocol Suite

  3. 3.1 Local Area Networks A local area network (LAN) is a data communication system that allows a number of independent devices to communicate directly with each other in a limited geographic area such as a single department, a single building, or a campus. A large organization may need several connected LANs. The most popular LANs are Ethernet and wireless LANs. TCP/IP Protocol Suite

  4. Figure 1 Carrier sense multiple access with collision detection ( CSMA/CD) LAN is a communication medium shared by multiple users. TCP/IP Protocol Suite

  5. Figure 2Ethernet layers Response for Flow and error control Responsible for the operation of the CSMA/CD access method Ethernet layer is above physical layer including logical link control and Media access control sub-layers TCP/IP Protocol Suite

  6. Figure 3Ethernet frame Used for synchronization Identify the frame start TCP/IP Protocol Suite

  7. 3.2 Point-to-Point WANs A second type of network we encounter in the Internet is the point-to-point wide area network. A point-to-point WAN connects two remote devices using a line available from a public network such as a telephone network. TCP/IP Protocol Suite

  8. Figure 456K modem PCM: Pulse code modulation TCP/IP Protocol Suite

  9. Note: ADSL (Asynchronous digital subscriber line) is an asymmetric communication technology designed for residential users;it is not suitable for businesses. TCP/IP Protocol Suite

  10. Figure 5Bandwidth division in ADSL Telephone call TCP/IP Protocol Suite

  11. Figure 6ADSL and DSLAM Digital subscriber line access multiplexer TCP/IP Protocol Suite

  12. Figure 7Cable bandwidth TCP/IP Protocol Suite

  13. Figure 8Cable modem configurations Cable modem transmission system TCP/IP Protocol Suite

  14. Table 1 Synchronous Optical Network (SONET) rates STS: synchronous transport signal 5 Gbps 10 Gbps TCP/IP Protocol Suite

  15. 3.3 Switched WANs The backbone networks in the Internet are usually switched WANs. A switched WAN is a wide area network that covers a large area (a state or a country) and provides access at several points to the users. Inside the network, there is a mesh of point-to-point networks that connects switches. The switches, multiple port connectors, allow the connection of several inputs and outputs. X.25 Frame relay Asynchronous Transfer Mode (ATM) TCP/IP Protocol Suite

  16. Note: A cell network uses the cell as the basic unit of data exchange. A cell is defined as a small, fixed-size block of information. TCP/IP Protocol Suite

  17. Figure 9Architecture of an ATM network ATM: asynchronous transfer mode UNI: User-to-network interface NNI: Network-to-network interface TCP/IP Protocol Suite

  18. Figure 10Virtual circuits VCI: Virtual circuit identifier VPI: Virtual path identifier TCP/IP Protocol Suite

  19. Note: Note that a virtual connection is defined by a pair of numbers: the VPI and the VCI. TCP/IP Protocol Suite

  20. Figure 11An ATM cell ATM cell is a 53-byte packet TCP/IP Protocol Suite

  21. 3.4 Connecting Devices LANs or WANs do not normally operate in isolation. They are connected to one another or to the Internet. To connect LANs or WANs, we use connecting devices. Connecting devices can operate in different layers of the Internet model. We discuss three kinds of connecting devices: repeaters (or hubs),bridges (or two-layer switches), and routers (or three-layer switches). Repeaters and hubs operate in the first layer of the Internet model. Bridges and two-layer switches operate in the first two layers. Routers and three-layer switches operate in the first three layers TCP/IP Protocol Suite

  22. Figure 13Connecting devices Router is a three-layer device (physical, data link and network layers) Bridge is a two-layer device (physical and data link layers) Repeater is a physical layer device TCP/IP Protocol Suite

  23. Figure 14Repeater A repeater connects segments of a LAN. A repeater forwards every bit; it has no filtering capability. TCP/IP Protocol Suite

  24. Figure 15Function of a repeater A repeater is a regenerator, not an amplifier. TCP/IP Protocol Suite

  25. Figure 16Bridge A bridge has a table used in filtering decisions. TCP/IP Protocol Suite

  26. Figure 17Learning bridge A bridge does not change the physical (MAC) addresses in a frame. TCP/IP Protocol Suite

  27. Figure 18Routing example A router is a three-layer physical, data link, and network) device. A router changes the physical addresses in a packet. TCP/IP Protocol Suite

  28. Note: A repeater or a bridge connects segments of a LAN. A router connects independent LANs or WANs to create an internetwork (internet). TCP/IP Protocol Suite

  29. Gateways • The term “Gateway” is used with different meanings in different contexts • “Gateway” is a generic term for routers (Level 3) • “Gateway” is also used for a device that interconnects different Layer 3 networks and which performs translation of protocols (“Multi-protocol router”) TCP/IP Protocol Suite

  30. Interconnection Many times it is necessary to connect a local area network to another local area network or to a wide area network. Local area network to local area network connections are often performed with a bridge-like device. Local area network to wide area network connections are usually performed with a router. A third device, the switch, can be used to interconnect segments of a local area network. TCP/IP Protocol Suite

  31. Why Interconnect? To separate / connect one corporate division with another. To connect two LANs with different protocols. To connect a LAN to the Internet. To break a LAN into segments to relieve traffic congestion. To provide a security wall between two different types of users. TCP/IP Protocol Suite

  32. An Example of Internetworking TCP/IP Protocol Suite

  33. Transparent Bridges-I A transparent bridge does not need programming but observes all traffic and builds routing tables from this observation. This observation is called backward learning. Each bridge has two connections (ports) and there is a routing table associated with each port. A bridge observes each frame that arrives at a port, extracts the source address from the frame, and places that address in the port’s routing table. A transparent bridge is found with CSMA/CD LANs. TCP/IP Protocol Suite

  34. Transparent Bridges-II A transparent bridge can also convert one frame format to another, but this does not happen too often anymore since most networks are CSMA/CD. Note that some people / manufacturers call a bridge such as this a gateway or sometimes a router. The bridge removes the headers and trailers from one frame format and inserts (encapsulates) the headers and trailers for the second frame format. TCP/IP Protocol Suite

  35. Remote Bridges A remote bridge is capable of passing a data frame from one local area network to another when the two LANs are separated by a long distance and there is a wide area network connecting the two LANs. A remote bridge takes the frame before it leaves the first LAN and encapsulates the WAN headers and trailers. When the packet arrives at the destination remote bridge, that bridge removes the WAN headers and trailers leaving the original frame. TCP/IP Protocol Suite

  36. An Example of Remote Bridges TCP/IP Protocol Suite

  37. Loop in Connected LANs What happens if you have many LANs interconnected with multiple bridges? Data that leaves one workstation could travel to a bridge, across the next network, into the next bridge, and back onto the first network. A packet may continue to cycle like this forever! TCP/IP Protocol Suite

  38. F F F F F F Danger of Loops • Consider the two LANs that are connected by two bridges. • Assume host n is transmitting a frame F with unknown destination. What is happening? • Bridges A and B flood the frame to LAN 2. • Bridge B sees F on LAN 2 (with unknown destination), and copies the frame back to LAN 1 • Bridge A does the same. • The copying continues Where’s the problem? What’s the solution ? F TCP/IP Protocol Suite

  39. Spanning Tree Algorithm How do we stop this from happening? Disconnect one of the bridges? Maybe we want bridge redundancy in case one bridge fails. How about applying the spanning tree algorithm. How is the algorithm applied? TCP/IP Protocol Suite

  40. Spanning Tree Protocol (IEEE 802.1d) • The Spanning Tree Protocol (SPT) is a solution to prevent loops when forwarding frames between LANs • The SPT is standardized as the IEEE 802.1d protocol • The SPT organizes bridges and LANs as spanning tree in a dynamic environment • Frames are forwarded only along the branches of the spanning tree • Note: Trees don’t have loops TCP/IP Protocol Suite

  41. Spanning Tree Protocol (IEEE 802.1d) • Bridges that run the SPT are called transparent bridges • Bridges exchange messages to configure the bridge ( Configuration Bridge Data Unit or BPDUs) to build the tree. TCP/IP Protocol Suite

  42. Virtual LAN (VLAN) Virtual LANs A virtual LAN, or VLAN, is a logical subgroup within a local area network that is created via switches and software rather than by manually moving wiring from one network device to another Even though the employees and their actual computer workstations may be scattered throughout the building, LAN switches and VLAN software can be used to create a “network within a network.” TCP/IP Protocol Suite

  43. VLAN A relatively new standard, IEEE 802.1Q, was designed to allow multiple devices to intercommunicate and work together to create a virtual LAN Instead of sending a technician to a wiring closet to move a workstation cable from one switch to another, an 802.1Q-compliant switch can be remotely configured by a network administrator TCP/IP Protocol Suite

  44. Review of LAN TCP/IP Protocol Suite

  45. What is a VLAN TCP/IP Protocol Suite

  46. VLAN TCP/IP Protocol Suite

  47. Why do we need VLAN TCP/IP Protocol Suite

  48. VLAN Tagging TCP/IP Protocol Suite

  49. IEEE 802.1Q:Features-I TCP/IP Protocol Suite

  50. IEEE 802.1Q:Features-II TCP/IP Protocol Suite

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