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Semester 1 CHAPTER 11

Semester 1 CHAPTER 11. Content. Layer 3 Devices ARP concept Network layer services Routed and routing protocols Protocol analyzer. LAYER 3 DEVICES AND NETWORK TO NETWORK COMMUNICATION. Internetworking. Path determination.

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Semester 1 CHAPTER 11

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  1. Semester 1CHAPTER 11

  2. Content • Layer 3 Devices • ARP concept • Network layer services • Routed and routing protocols • Protocol analyzer

  3. LAYER 3 DEVICESANDNETWORK TO NETWORK COMMUNICATION

  4. Internetworking

  5. Path determination • Path determination is the process that the router uses to choose the next hop in the path for the packet to travel to its destination based on the link bandwidth, hop, delay ...

  6. Router • A router is a type of internetworking device that passes data packets between networks, based on Layer 3 addresses. • A router has the ability to make intelligent decisions regarding the best path for delivery of data on the network.

  7. IP addresses • IP addresses are implemented in software, and refer to the network on which a device is located. • IP addressing scheme, according to their geographical location, department, or floor within a building. • Because they are implemented in software, IP addresses are fairly easy to change.

  8. Router and Bridge

  9. Router connections • Routers connect two or more networks, each of which must have a unique network number in order for routing to be successful. • The unique network number is incorporated into the IP address that is assigned to each device attached to that network.

  10. Router Interface

  11. Router function

  12. Router function (cont.1) Strips off the data link header, carried by the frame. (The data link header contains the MAC addresses of the source and destination.)

  13. Router function (cont.2) Examines the network layer address to determine the destination network.

  14. Router function (cont.3) Consults its routing tables to determine which of its interfaces it will use to send the data, in order for it to reach its destination network.

  15. Router function (cont.4) Send the data out interface B1, the router would encapsulate the data in the appropriate data link frame.

  16. Router Interface example • Interface is a router’s attachment to a network, it may also be referred to as a port. In IP routing. • Each interface must have a separate, unique network address.

  17. IP address assignment static addressing and dynamic addressing

  18. Static addressing • You must go to each individual device and configure it with an IP address. • You should keep very meticulous records, because problems can occur on the network if you use duplicate IP addresses.

  19. Dynamic addressing • There are a few different methods that you can use to assign IP addresses dynamically: • RARP: Reverse Address Resolution Protocol. • BOOTP: BOOTstrap Protocol. • DHCP: Dynamic Host Configuration Protocol.

  20. RARP server Dynamic addressing: RARP RARP Request RARP Reply MAC: Known IP: Unknown

  21. BOOTP server Dynamic addressing: BOOTP UDP Broadcast UDP Broadcast MAC: Known IP: Unknown IP Address Gateway IP of server Vendor-specific MAC1 – IP1 MAC2 – IP2 MAC3 – IP3

  22. DHCP server Dynamic addressing: DHCP DHCP Discover UDP Broadcast DHCP Offer UDP Broadcast DHCP Request DHCP Ack MAC: Known IP: Unknown IP Address Gateway IP of servers And more … IP1 IP2 IP3

  23. Review • The role of router in network. • Address assignment. • Static addressing. • Dynamic addressing.

  24. ARP CONCEPT

  25. Encapsulation

  26. Address resolution protocol • In order for devices to communicate, the sending devices need both the IP addresses and the MAC addresses of the destination devices. • When they try to communicate with devices whose IP addresses they know, they must determine the MAC addresses. • ARP enables a computer to find the MAC address of the computer that is associated with an IP address.

  27. Address resolution protocol

  28. ARP table in host RAM

  29. MAC A.B.C.1.2.3 MAC ? IP 10.0.2.1 IP 10.0.2.9 Data 10.0.2.1 10.0.2.9 10.0.2.5 A.B.C.1.2.3 A.B.C.7.8.9 A.B.C.4.5.6 A B C ARP operation ARP Table: ?

  30. MAC A.B.C.1.2.3 MAC ff.ff.ff.ff.ff.ff IP 10.0.2.1 IP 10.0.2.9 What is your MAC Addr? 10.0.2.1 10.0.2.9 10.0.2.5 A.B.C.1.2.3 A.B.C.7.8.9 A.B.C.4.5.6 A B C ARP operation: ARP request

  31. MAC A.B.C.1.2.3 MAC ff.ff.ff.ff.ff.ff IP 10.0.2.1 IP 10.0.2.9 What is your MAC Addr? 10.0.2.1 10.0.2.9 10.0.2.5 A.B.C.1.2.3 A.B.C.7.8.9 A.B.C.4.5.6 A B C ARP operation: Checking That is my IP

  32. MAC A.B.C.7.8.9 MAC A.B.C.1.2.3 IP 10.0.2.9 IP 10.0.2.1 This is my MAC Addr 10.0.2.1 10.0.2.9 10.0.2.5 A.B.C.1.2.3 A.B.C.7.8.9 A.B.C.4.5.6 A B C ARP operation: ARP reply

  33. MAC A.B.C.1.2.3 MAC A.B.C.7.8.9 IP 10.0.2.1 IP 10.0.2.9 Data 10.0.2.1 10.0.2.9 10.0.2.5 A.B.C.1.2.3 A.B.C.7.8.9 A.B.C.4.5.6 A B C ARP operation: Caching ARP Table: A.B.C.7.8.9 – 10.0.2.9

  34. ARP: Destination local

  35. Internetwork communication • How to communicate with devices that are not on the same physical network segment.

  36. Default gateway • In order for a device to communicate with another device on another network, you must supply it with a default gateway. • A default gateway is the IP address of the interface on the router that connects to the network segment on which the source host is located. • In order for a device to send data to the address of a device that is on another network segment, the source device sends the data to a default gateway.

  37. Proxy ARP • Proxy ARP is a variation of the ARP. • In the case the source host does not have a default gateway configured. ARP Reply

  38. ARP: Destination not local

  39. Is the MAC address in my ARP cache Send an ARP request N Y Get an ARP reply Send Data ARP Flowchart Send Data to a device

  40. ARP table in router • The router interface connected to the network has an IP address for that network. • Routers, just like every other device on the network, send and receive data on the network. • If router connects to a LAN, it builds ARP tables that maps IP addresses to MAC addresses in that interface.

  41. ARP table in routers and in hosts

  42. Review • What is the purpose of ARP protocol? • How does ARP protocol work? • What is the role of default gateway? • What is proxy ARP?

  43. NETWORK LAYER SERVICES

  44. Connection oriented network services • A connection is established between the sender and the recipient before any data is transferred.

  45. Circuit switched • Connection-oriented network processes are often referred to as circuit switched. • These processes establish a connection with the recipient, first, and then begin the data transfer. • All packets travel sequentially across the same physical circuit, or more commonly, across the same virtual circuit.

  46. Connectionless network services • They treat each packet separately. • IP is a connectionless system.

  47. Packet switched • Connectionless network processes are often referred to as packet switched. • When the packets pass from source to destination, they can: • Switch to different paths. • Arrive out of order. • Devices make the path determination for each packet based on a variety of criteria. Some of the criteria may differ from packet to packet.

  48. Review • Comparing connectionless and connection-oriented services. • IP is a connectionless system.

  49. ROUTED AND ROUTING PROTOCOLS

  50. Network protocols • In order to allow two host communicate together through internetwork, they need a same network protocol. • Protocols are like languages. • IP is a network layer protocol.

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