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Introduction to TCP/IP (Topic 5)

Introduction to TCP/IP (Topic 5). Textbook: Networking Basics, CCNA 1 Companion Guide , Cisco Press Cisco Networking Academy Program, CCNA 1 and 2, Companion Guide , Cisco Press, Latest Edition. TCP/IP Model. TCP/IP was first developed as part of a contract from the US DoD.

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Introduction to TCP/IP (Topic 5)

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  1. Introduction to TCP/IP(Topic 5) Textbook: Networking Basics, CCNA 1 Companion Guide, Cisco Press Cisco Networking Academy Program, CCNA 1 and 2, Companion Guide, Cisco Press, Latest Edition CIM 2465 Intro to TCP/IP

  2. TCP/IP Model • TCP/IP was first developed as part of a contract from the US DoD CIM 2465 Intro to TCP/IP

  3. TCP/IP Network Access Layer (1) • Also known as Network Interface Layer • Defines how computers and networking devices should access a physical medium to send bits to others • Match OSI Layers 1 and 2 • Does not actually define any network access layer standards, but refers to other well-defined standards • Note that ARP, proxy ARP, and RARP mainly work at TCP/IP’s internet layer, but they provide an interface to the network access layer CIM 2465 Intro to TCP/IP

  4. TCP/IP Network Access Layer (2) • Fig 9-2 CIM 2465 Intro to TCP/IP

  5. TCP/IP Internet Layer • Defines how to deliver data from one host to another (over multiple different physical networks) • By separating its logic from the underlying networking details, thus allows hosts, networking devices, routers, to use the same processes and logic regardless of the underlying physical networks being used • Logical Addressing (IP addresses for each network interface) • Routing • Defines several protocols, most important being the Internet Protocol (IP) CIM 2465 Intro to TCP/IP

  6. Key Internet Layer Protocols CIM 2465 Intro to TCP/IP

  7. Basic IP Routing • IP routing defines how to forward data, in form of IP packets, from one host to another • Fig 9-3 CIM 2465 Intro to TCP/IP

  8. IP Packets • An IP packet is the header defined by the IP protocol, along with any higher-layer protocol headers and the end-user data • Basic IP Packet format CIM 2465 Intro to TCP/IP

  9. How IP Routing uses IP Addresses • Routers use IP routing tables to tell them out which interfaces to forward packets • To make routing efficient • IP addresses for hosts on the same physical network must have the same value in the first part of the addresses (network address) • Each group then need one entry in the routing table • Fig 9-5 CIM 2465 Intro to TCP/IP

  10. CIM 2465 Intro to TCP/IP

  11. TCP/IP Transport Layer • To provide the service of taking data from one application process on one computer and delivering that data to the correct application process on another computer • Compare with the Internet Layer, the internet layer delivers data packets from one computer to another, but it does not think about which application sent the data or which application on the receiving computer needs the data CIM 2465 Intro to TCP/IP

  12. Fig 9-6 • Two main Transport Layer protocols • Transmission Control Protocol (TCP) • User Datagram Protocol (UDP) CIM 2465 Intro to TCP/IP

  13. TCP Vs UDP CIM 2465 Intro to TCP/IP

  14. TCP/IP Application Layer • Provides services to applications • Fig 9-7 CIM 2465 Intro to TCP/IP

  15. Application Layer Protocols CIM 2465 Intro to TCP/IP

  16. Application Layer Protocols CIM 2465 Intro to TCP/IP

  17. Application Layer Protocols CIM 2465 Intro to TCP/IP

  18. TCP/IP Internetworks CIM 2465 Intro to TCP/IP

  19. Routing Fundamentals • Routers have two main functions • Perform end-to-end delivery of IP packets from the sending host to the receiving host. • Receive packets • Decide to which router or host to send the packets next • Forward them • Maintain a Routing Table with the best routes to reach each possible destination, using some routing protocols CIM 2465 Intro to TCP/IP

  20. IP Routing (1) • Layer 2 devices, such as LAN switches, can forward data on only Ethernet links (within the same network), it cannot connect to WAN links (to other networks), as the physical and datalink standards are different • Routers, can connect to multiple types of physical network (internetworking) • So, routers can receive IP packets sent by computers and send the packets over any physical networks, to deliver the packets to the destinations. This forwarding process is called IP routing or IP forwarding CIM 2465 Intro to TCP/IP

  21. IP Routing (2) • A router examines incoming packets, looks at the destination IP address, and decides out which interface to forward the packet • Routing process relies on each router knowing how to route IP packets based on its IP routing table • Routers use routing protocols (e.g. RIP, EIGRP), to dynamically learn the required routes CIM 2465 Intro to TCP/IP

  22. Some Key Terms • Routing / Forwarding • The process of received packets, deciding where to forward them next, and forwarding them • Routed protocol / Routable protocol • A protocol that defines a packet that can be forwarded by a routing process • E.g. IP, IPX (Netware) are routable, NetBEUI is non-routable • Routing protocol • A protocol used between routers so that they can dynamically learn routes to add to their routing tables CIM 2465 Intro to TCP/IP

  23. Routing between Two Connected LAN Subnets • The router has an interface physical attached to each of the two LANs CIM 2465 Intro to TCP/IP

  24. IP-Centric Perspective No changes to source and destination IP address CIM 2465 Intro to TCP/IP

  25. Note that the router will remove the Ethernet header/trailer and encapsulate a new one Note the changes of MAC addresses CIM 2465 Intro to TCP/IP

  26. IP Routing: Host Perspective (1) CIM 2465 Intro to TCP/IP

  27. IP Routing: Host Perspective (2) • Decision • If the destination IP address is on my same IP network/subnet, send the packet directly to that host • If the destination IP address is not on my same IP network/subnet, send the packet to my default router (default gateway) CIM 2465 Intro to TCP/IP

  28. Main steps of IP routing • P.400 of the textbook CIM 2465 Intro to TCP/IP

  29. More Detailed Routing Steps CIM 2465 Intro to TCP/IP

  30. Perspectives on WAN Routing • R1, R2 configured to use Serial interface and a data link protocol PPP (Point-to-Point Protocol) CIM 2465 Intro to TCP/IP

  31. Important Characteristics of IP • IP is Unreliable • The protocol does not attempt to perform any error recovery of data (lost data) • How to have Reliable transmission • Uses TCP transport layer protocol, which performs error recovery • The application itself performs the error recovery • IP is Connectionless CIM 2465 Intro to TCP/IP

  32. Connectionless Vs Connection-oriented • Connectionless • The sender and receiver do not pre-arrange for communication to occur • E.g. IP, Ethernet, UDP • Analogy: mailing a letter • Connection-oriented • The sender and receiver must pre-arrange for communication to occur • E.g. TCP, Frame Relay • Analogy: make a phone call CIM 2465 Intro to TCP/IP

  33. Full IP Header • Table 10-4 for details CIM 2465 Intro to TCP/IP

  34. Routing Protocols • Used by routers to learn routes • When a collection of routers uses the same IP routing protocol, the routers exchange messages and update their own routing tables • HOW? • Connected subnets • Static Routes • Routing protocols CIM 2465 Intro to TCP/IP

  35. Learning Connected Routes • Subnets to which a router’s interfaces are connected are called connected subnets • Routers automatically add routes to their IP routing tables for directly connected subnets CIM 2465 Intro to TCP/IP means “Connected”

  36. Static Routes • Add routes to routing tables via router configuration • E.g. a Cisco router command to R1 (interface FA0/1) of Fig 10-11 ip route 172.16.3.0 255.255.255.0 172.162.2.252 will add an entry to R1 S 172.16.3.0 255.255.255.0 Fa0/1 172.16.2.252 (S means “Static”) CIM 2465 Intro to TCP/IP

  37. Learning by Routing Protocols • Each router sends messages to the routers attached to the same subnets, which essentially list all the routing information each router knows. Thus all routers learns all the routes. CIM 2465 Intro to TCP/IP

  38. RIP (Routing Information Protocol) • R2 knows a connected route to 172.16.3.0, so RIP then advertises this route to R1 CIM 2465 Intro to TCP/IP

  39. Using Metrics to Pick the Best Routes • Routing protocols must be able to choose between competing alternative routes CIM 2465 Intro to TCP/IP

  40. Using Metrics to Pick the Best Routes • By Metric, some kind of measurement • Allows a router to measure how good each route is • Hop Count (RIP) • Bandwidth, Delay, Loading, Reliability (IGRP, EIGRP) • Cost (OSPF) • Clock Ticks (Novell IPX) CIM 2465 Intro to TCP/IP

  41. Routing Protocol Metrics CIM 2465 Intro to TCP/IP

  42. CIM 2465 Intro to TCP/IP

  43. CIM 2465 Intro to TCP/IP

  44. Routing Protocol Algorithms • Distance Vector Algorithms • “distance to neighboring routers” as the metric (e.g. Hop count in RIP) • No information about the topology of the network beyond the neighboring routers • Link State Algorithms • Advertise information about the entire topology • Shortest Path Algorithm • Hybrid Algorithms CIM 2465 Intro to TCP/IP

  45. Classless Vs Classful Routing Protocols • Variable-length Subnet Masking (VLSM) • Provides a great deal of flexibility when subnetting a single Class A, B, or C network • Different subnet masks can be used on different subnets of the same Class A, B, or C network • Allows network engineers to reduce the number of wasted IP addresses • A Classful routing protocol does not send subnet masks in routing updates, so it cannot support VLSM • A Classless routing protocol does send subnet masks in routing updates, so it does support VLSM CIM 2465 Intro to TCP/IP

  46. CIM 2465 Intro to TCP/IP

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