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Introduction

Introduction. What are routers (Ponta) Data Conversion (Adrian) Routing (Albert) Routers (Jordan) Router Architecture (Victor). Routers vs. Computer. What is a computer? A general purpose machine that takes an input translates the input under software control and gives an output.

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Introduction

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  1. Introduction • What are routers (Ponta) • Data Conversion (Adrian) • Routing (Albert) • Routers (Jordan) • Router Architecture (Victor)

  2. Routers vs. Computer • What is a computer? • A general purpose machine that takes an input translates the input under software control and gives an output. • A router is also a computer • not a “general purpose machine” • Main purpose is to route data

  3. Networks • Today’s networks are large masses of routers • Routers take any form of data such as email, web-browser requests, and file transfers and deliver them to the appropriate destinations. • The internet is a large network of interconnected routers.

  4. Routing in a nutshell • Routers work by reading the IP address of data packets and determines the correct source and destination for the packet. • The router can also discover the best way to get the packet to its destination.

  5. Routing in a nutshell (cont.) • Routers take requests from their local users and forward those requests to the appropriate host.

  6. Routing • Routing is the process that allows data to travel from one host to another • Routing is responsible for the making the Internet work.

  7. Without Routers • Every computer would have to be connected together • Users would need to know • the address of every website they wanted to visit • All the computers you would need to pass through to get to the destination computer.

  8. Accessing Websites • You enter a URL address in to your web browser (e.g. Internet Explorer, Netscape Navigator, etc.), e.g, http://www.csun.edu • The browser sends a message to the router • The message notifies that you want to see the information stored at www.csun.edu • The process begins

  9. Internet Explorer

  10. Netscape

  11. Address Conversion • DNS servers translate the alphanumeric URL, www.csun.edu, address to an IP address: 130.166.1.55 • Packets are sent to the routers that read this address

  12. Routing Packets • Each router examines the packet • Determines the IP address • Matches the information against its own routing table. • Chooses which port to route it out of

  13. Routing Table • A two column table • First column identifies each router in the network • Second column lists the router to which each router should send data to

  14. Routing Table • Router examines packet • If exact match, forwards the message • If there is no match, it runs though table again, looking for a match • If still no match, router sends the packet out of the default next-hop address

  15. Routing Table • Router sends an ICMP() “host unreachable” or “network unreachable” message back to sender ultimately if no match is found. • Difficult part of router’s job is not how it routes, but how it builds up its table

  16. Routing Table Example

  17. Routing Packets This process continues until the request finally reaches www.csun.edu

  18. Routing • The routing tables have been keeping track of the path to the destination. • The routing path is now known by the initial router.

  19. Routing Algorithms • Routing algorithm • complex set of rules that take into account a variety of factors • Determines what is the best via routing algorithm • Selects the best path between the source and destination machine

  20. Routing Issues

  21. Flooding the Network • Early routers were slow • The networks they ran on were equally low-powered, with little bandwidth • Isolated in that they did not exchange routing tables • As a result routers forwarded data by flooding every path with packets

  22. How can we solve this? • Backward learning-router remembers the source addresses of all incoming packets and notes the physical interface it came in on • Static Routing • Rely either on a human or host computer to make these decisions • Source routing-end hosts place information in every packet they place on the network

  23. Centralized vs. Decentralized

  24. Centralized Routing • All routing decisions are made by one central computer or router • Typically used in host computers • All computers are connected to the central computer

  25. Decentralized Routing • All computer or routers in the network make their own routing decisions • In larger networks, routing table is developed by the network manager • In smaller networks, routing table is developed by one individual • Most decentralized routing protocols can automatically adapt to changes in the network configuration

  26. Static vs. Dynamic Routing

  27. Static Routing • Routing decisions are made in a decentralized manner • When new computers are added to network, they announce their presence • Commonly used in networks that have few routing options that seldom change

  28. Dynamic Routing • Routing decisions are made in a decentralized manner by individual computers • Used when there are multiple routes through a network • Routes messages over the fastest possible route

  29. Router A Router B Router C Router D Dynamic Routing • Distance vector dynamic routing • Routers count the number of hops along a route. • Routers periodically exchange information on the hop count

  30. Dynamic Routing • Link state dynamic routing • Rather than knowing a route’s distance, link state routing tries to determine how fast each possible route is • Routers periodically exchange this information to other routers in the network • Preferred over distance vector protocols because they converge quicker

  31. Dynamic Routing-Drawbacks • Requires more processing by each computer or router in the network • Transmission of routing information wastes network capacity.

  32. Connectionless Routing • Used when a message can fit into one single packet • Each packet is routed independently • A router must make a decision for each packet • Used by UDP (User Datagram Protocol) to send short control messages

  33. Connection-Oriented Routing • Sets up a virtual circuit between the sender and receiver • Packets from the same message use the same route VC1 VC2

  34. Router Types • Home Routers • Small Organization and Office Routers • High End Routers

  35. Home Routers • Usually simple • Examples includes: • Linksys, Cable/DSL, 10/100 Ethernet backbone Features: • Voice over IP telephone installed by Netphone.

  36. D-LINK-614+ • 22mbps “Air Plus” is twice as fast as the usual (11-mbps) 802.11b connection • Utilizes Texas Instruments patented Digital Signal Processing • Offers 256-bit encryption • the strongest available • Deep firewall configuration options. • Firewall features are easy to implement • Example: Can designate particular computers as WEB servers or FTP servers which are visible to the Internet

  37. D-LINK-614+

  38. Small Organization and Office Routers • Slightly larger routers • Do little more than home router • These routers enforce rules concerning security for the office network.

  39. 3-Com-Superstack • Provides: • Low equipment costs • Dial-in/dial-out • Frame Relay • Lease Line PPP Connection

  40. 3-Com Superstack cont. • Contains: • Three stackable components • That provides multi-protocol remote access server • Full function WAN router technology for small and medium sized business. • Offers secure access Authentication

  41. 3-Com Superstack cont. • In addition: • it can proxy or relay IP address to another central server. • Simplifies network administration • Enhances the mobility of both remote and local users.

  42. High-End Routers • Largest routers • Handle million of packets every second • Work to configure the network efficiently • Large stand alone systems

  43. Nortel Networks • High end routers manufacturer • Provides large high performance, scalable routing devices. • Backbone Node and Backbone Concentrator Node

  44. Benefits of the Nortel Networks • Enhance network performance • High Network availability • Network investment protection

  45. IBM 2210 Nways Multiprotocol • Provides network solutions for a range of applications • This allows: • System administrators to build and manage scalable Web Servers. • Superior to Domain Name Servers round robin-querying

  46. Router Architecture

  47. Router Memory • Flash • ROM • Cache • RAM

  48. Router Memory • Flash • Location where the basic boot image is stored.

  49. Router Memory • ROM • Initializes the processor hardware and boots the operating system software. • Runs when the router is powered up or reset

  50. Router Memory • Cache • Primary • Primary cache is closest to the processor core and has the fastest access • Secondary • Secondary cache has slower access than primary cache, but faster access than tertiary cache. • Trietary • Slowest of all cache but faster than RAM

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