1 / 68

Bridges, Routers and Switches Part One

Bridges, Routers and Switches Part One. Three things are certain: Death, taxes, and lost data. Guess which has occurred. Haiku error message. Bridging . Bridges connect two independent LANs to form internetworks. Types of Bridges. Transparent Source Routing Transnational. Bridges.

nadda
Download Presentation

Bridges, Routers and Switches Part One

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Bridges, Routers and SwitchesPart One Three things are certain: Death, taxes, and lost data. Guess which has occurred. Haiku error message

  2. Bridging • Bridges connect two independent LANs to form internetworks

  3. Types of Bridges • Transparent • Source Routing • Transnational

  4. Bridges • Each LAN is referred to as a Network Segment

  5. Bridge Ports • Bridge Ports connect the Bridge to the Network • Consist of a Network Interface (Ethernet, Token Ring, FDDI)

  6. Bridges Form One Logical Network

  7. Bridging and ISO Model • Bridges function at at the Media Access (MAC) layer

  8. Bridging and ISO Model • Bridges “see” the network at the MAC layer • Bridges make forwarding decisions based on MAC (Physical) addresses

  9. Bridging and ISO Model • Bridges have no knowledge of paths between address • Bridges are transparent to higher level protocol • Bridges are protocol independent, the same bridge can pass IP, IPX, DecNet traffic

  10. Transparent Bridges • Usually used on Ethernet networks • Called Transparent because nodes are not aware of its presence • Defined by IEEE 802.1 standard • Forwards frames between networks • Self learning

  11. Transparent Bridges • Maintains a data base of all known node address on each port

  12. Transparent Bridges • Transparent Bridges are self learning • Examine every frame which passes a port • Determines the source address • Compares each address to its data base • If address is not in data base then the bridge adds the address

  13. Transparent Bridges

  14. Transparent Bridge Frame Forwarding • Examines Destination address • If address is on the same LAN as the incoming port, ignores the frame • If Not • Looks up destination address in its Data Base • If Address is found • Forward out the appropriate Port • If Address is not found • Forwards out all Ports

  15. Spanning Tree Algorithm

  16. Spanning Tree Algorithm

  17. Spanning Tree Algorithm

  18. Spanning Tree Algorithm

  19. Spanning Tree Algorithm • Eliminates all active loops in the network by creating a set of paths with only one path between each node • Bridges negotiate which paths are to remain open and which paths will be blocked • If a path becomes inaccessible, the bridges will reconfigure the network, creating a new spanning tree and new set of paths

  20. Source Route Bridging • Only used in Token Ring environments

  21. Source Route Bridging • NOTE: Despite its name Source Routing is Bridging and takes place at the MAC layer

  22. Source Route Bridging • Node maintain their own routing table • When a frame is transmitted to a node on another ring, the packet must contain the route or path • Node “discovers” the route by sending out an Explorer Frame with the address of the destination Node • Depending on the protocols used the node may send an All Route Exploder Frame or a Singe Route Explorer Frame

  23. Source Route Bridging • The route explorer frame records the Bridge Number and Ring Number of all bridges and networks crossed • When it reaches the destination node, the destination node sets a flag and transmits the frame back to the sending node • The Route Explorer Frame now has the route to the destination station • If two Routes return to the sending node, it usually uses the first route received

  24. Source Route Bridging

  25. Source Route Bridging • Source Route Bridges can connect rings running at different speeds

  26. What’s Wrong with Source Routing? • Takes processing resources of end nodes • Each Ring and Bridge must be assigned a Ring Number and Bridge Number - Any error in assigning these numbers causes fatal errors • Fatal errors happen often

  27. Source Route Bridging

  28. Source Route Bridging • Allows loops • How many paths though this network?

  29. Source Route Bridging • What else is wrong with Source Routing? • What is good about Source Routing?

  30. Source Route and Transparent Bridges in Same Network • Usually not very reliable - may work in some simple networks • Source Routed traffic can only cross Source Route Bridges

  31. Transnational Bridges • Connect two dissimilar topologies

  32. Advantages of Bridging • Easy to install and configure • Inexpensive • Transparent to Network • Automatically adapt to Network Changes • Bridge unroutable protocols

  33. Disadvantages of Bridges • Can not take advantage of redundant paths in the network • Can not prevent Broadcast Storms • Because bridges form a single logical network the network becomes large and therefore difficult to manage

  34. Routers What makes a Protocol Routable • To be routable a protocol must assign addresses so that the address contain Network and Node address • Routable Protocols include • IP • IPX • DecNet • Vines • Non-Routable Protocols • NetBios

  35. Routers • Function of a Router is to efficiently forward packets between networks • Very often more than one path exists, a router must chose the “best” path • Routers function at the Network layer of the OSI Model, routing decisions are made using the address assigned by a Network layer protocol such as IP

  36. Routers • Since routers function at the Network layer routers are protocol dependent devices • Must support IP, IPX, AppleTalk, DecNet, etc.

  37. Routers • Multiple Protocols • Most routers can route a verity of protocols • The ability to route multiple protocols is implemented in software

  38. Routers

  39. Routers • Routers can connect dissimilar LAN topologies • Routers can connect LANs to the WAN

  40. Routers - Why use Routers • Segment Networks • Congestion Control • Source Quench technique - Router can request a source to stop transmitting until congestion is relieved

  41. Routers • Bridges examine each frame on the network segment • Routers only receive packets addressed to them • Packets are addressed to routers from workstations or other routers

  42. Routers Node Configuration

  43. Routers Routing Tables • Routers maintain a Routing Table • The Routing Table instructs the router where (out which interface) to send the packet • Packets are routed one hop at a time

  44. Routers Routing Table

  45. Routers - Multiple Routes

  46. Routers Multiple Routes Routing Table Router 1 Target Net Next Hop Router Metric Net4 Attached 0 Net 1 Router 2 1 Net 1 Router 3 2 Net 3 Router 3 1 Net 3 Router 2 2 Net 2 Router 3 1 Net2 Router 2 2

  47. Routers Metric Values • Chose route with lowest Metric value • Metric value can represent: • Hops • Transmission Delay • Administrative Considerations (Cost) • Line Capacity

  48. Routers - Backup Links

  49. Routers - Routing Protocol • Routing Tables are dynamically created by the router • Router communicate with other routers to learn all paths through the network • This communication consists of all or portions of each routers routing table

  50. Routers - Routing Protocol • Routers use these Routing Tables to build a map of the network topology • The time it takes for all routers in a network to exchange routing tables is called Convergence • Router to Router communication is implemented according to Routing Protocols

More Related