Interconnecting devies

Introduction to all interconnecting devices in computer netwroks

1. INTERCONNECTING DEVICES

2. INTRODUCTION Inter connecting Devices: An Interconnecting device is any device that can enable computers to exchange data on a network. Backbone of a network.

3. Interconnecting Devices Hubs Repeaters Bridges Switches Routers Gateways

4. HUBS A hub is basically a multiport repeater .Hubs are a common connection point for devices in a network and are commonly used to connect segments of a LAN and have multiple ports. A hub takes the incoming data packet that comes into a port and copies it out to all the other ports in the hub.  It doesn't perform any filtering or redirection of data. It operates on physical layer of OSI model.

5. Hubs cannot filter data, so data packets are sent to all connected devices.

6. Hierarchy of hub

7. Two types of Hubs PASSIVE HUB: A passive hub is just a connector, it simply transmit and receive data from end devices connected to the LAN. It does not amplify the signal.

8. ACTIVE HUB: Active Hub is a hub which can amplify or regenerate the information signal. This type of hub has an advantage as it also amplifies the incoming signal as well as forward it to multiple devices. This hub is also known as Multiport Repeater . It strengthen the incoming signal before sending them to destination.

9. Advantages: Hub is less expensive. Active hubs can extend maximum network media distance. No processing is done at the hub to slow down performance.

10. Disadvantages: No intelligence to filter traffic. It will broadcast to all the ports which leads to inefficiencies and wastage .

11. REPEATERS Repeater is a device used to regenerate the signal over same network. A repeater connects segments of a LAN. A repeater is a device that operates only at the Physical layer of OSI model. As the distance of the two segments increases, the signal strength automatically keeps decreasing due to attenuation (loss of energy due to cable resistance and external noise factors). To overcome this, devices like repeaters that span long distances .

12. A Repeater in the OSI Model

13. A repeater connecting two segments of a lan

14. Function of Repeaters Repeaters receive signals from one network segment and it regenerates, and retransmit those signals to another network segment. When the signal becomes weak, they copy the signal bit by bit and regenerate it at the original strength . A repeater can extend only the physical length of network. A repeater forwards every frame; it has no filtering capability.

15. Function of a Repeater

16. A dvantages Extend length of network. It strengthen the weak signal. Remove the unwanted noise in an incoming signal.

17. D isadvantages It has no filtering capacity. It cannot connect two different architecture such as token ring and Ethernet etc.. Number of repeaters used must be least, otherwise cause propagation delay.

18. BRIDGES Bridge is a device used to connect two separate Ethernet networks into one extended Ethernet that uses same protocol. Bridging occurs at the data link layer of the OSI model, which means the bridge cannot read IP addresses, but only the outermost hardware address of the packet. The hardware address is also called the MAC (media access control) address.

19. A Bridge in the OSI Model

20. Function of a bridge When the frame enters it not only regenerates the signal it receives. As a data link layer device it checks the source and destination addresses in the frame. It maintains a table that maps addresses to ports. It send data frames only to the concerned destination. If destination address is in the same segment as the source address, stop transmit. Otherwise, forward to the other segment.

21. Function of a bridge

22. Types of Bridges BRIDGE MULTIPORT LEARNING SIMPLE

23. Simple Bridges A simple bridge connects two segments and contains table list of address of all the station included in them. The table of host addresses verses segment numbers entered manually. When new host added or existing deleted the table has to be updated. These are cheapest but also are error prone.

24. Learning Bridge A learning bridge build its table of content on its own, initially it is empty. When a frame comes to it, checks for the addresses in the table. If it is not present adds it to the table along with the segment number. The bridge continue checking and update its mapping table, so the name learning bridge.

25. Learning bridge

26. Multi-port Bridge When a simple or learning bridge connects more than two network segments it is called a multi-port bridge. It is a special case of either the simple or the learning bridge.

27. ADVANTAGES It minimizes unwanted traffic and it acts as a filter. It minimizes network congestion. Error links can be identified and then isolated. Bridges help to lower the data load over the data link layer.

28. DISADVANTAGES The speed is slower than repeaters but it is fast than that of the routers. Cost is expensive than repeaters but a bit cheaper than routers. Not able to handle multiple paths. Bridges are unable to read specific IP address; they are more concerned with the MAC addresses.

29. SWITCHES

30. SWITCHES

31. A network switch is a networking device that connects devices together on a computer networks, by using packet switching to receive, process and forward data to the destination device. It process the data at the datalink layer and network layer of the OSI model. Performs the datalink layer function, that is it looks at each packets or data unit and determines from a physical address(MAC address). Also called as Multilayer Switch because it works on two different layers.

32. FUNCTIONS Allows more than one device connected to the switch directly to transmit simultaneously. Can operates in Full-duplex mode(can send and receive frames at the same time). Performs MAC address recognition and frame forwarding in hardware.

33. Forwarding methods There are four forwarding methods available. 1. Store-and-forward: Switch buffers and verifies each frame before forwarding it. A frame is received fully before it is forwarded. Buffering will cause some delay.

34. Store-and-forward & Cut-through

35. Forwarding methods 2. Cut-through: Based on the destination address appears at the beginning of the MAC frame, the frame is directly sent to the appropriate output line if the output buffer is empty. If it is busy then, the switch falls back to store-and-forward operation. No error checking.

36. Forwarding methods 3. Fragment free A method that attempts to retain the benefits of both store and forward and cut through. Fragment free checks the first 64 bytes of the frame, where addressing information is stored. According to Ethernet, collisions should be detected during the first 64 bytes of the frame, so frames that are in error because of a collision will not be forwarded.

37. Forwarding methods 4. Adaptive Switching A method of automatically selecting between the other three modes. In specialized applications like Storage area networks, input and the output interfaces are the same bandwidth, this is not always general case in LAN’s. In LAN’s it is used for end user access that is, lower bandwidth and uplinks into a higher bandwidth.

38. Switch learning process When the switch receives a frame, it compares the source address of the frame with each entry in the forwarding table. If No match is found , the bridge will add to the table the frame source address and the interface on which the frame was received. If the match is found , the bridge updates the interface number on which the frame was received if it is different from the one in the table also it updates the record time.

39. Then, the switch compares the destination address of the frame with each entry in the forwarding table (MAC table). If a match is found then, The bridge compares the interface number on which the frame was received and the interface number in the table, if they are different the bridge forwards the frame through the interface number stored in the table. Otherwise if they are same the switches discards the frame. If no match found, the switch floods the frame on all interfaces except the one on which the frame was received.

40. Two layer switches Two layer switch operate at data link layer. Bridge is an example of two-layer switch. Bridge with few port can connect a few LAN’s. Bridge with many port may be able to allocate a unique port to each station, with each station on its own independent entity. This means no competing traffic.

41. Three layer switches Three layer switch operates at network layer. Example for three-layer switch is router. Routes packets based on their logical addresses (host to host addressing). A router normally connects LAN’s and WAN’s in the internet and has a routing table that is used for making decision about the route. The routing tables are normally dynamic and are updated using routing protocols.

42. Switch table

43. ADVANTAGES Only forwards frames as needed. Filters frames to avoid unnecessary load on segments. Sends frames only to segments that need to see them. Extends the geographical span of the network. Separate segments allow longer distances. Improves privacy by limiting scope of frames.

44. DISADVANTAGES While limiting broadcasts, switches are not as good as a routers. Handling multicast packets needs configuration and proper designing. It is difficult to reconfigure if any network error occurs in multicast. If switches are in promiscuous mode they are vulnerable to security attacks like spoofing IP address or capturing of Ethernet Frames. Higher cost.

45. ROUTERS

46. ROUTER A router is a three-layer device: It operates in the physical, data link, and network layers. As a physical layer device: It regenerates the signal it receives. As a data link layer device: The router checks the physical addresses (source and destination) contained in the packet. As a network layer device: A router checks the network layer addresses (addresses in the IP layer).

47. ROUTER A router can connect LANs together. A router can connect WANs together. A router can connect LANs and WANs together. In other words, a router is an internetworking device. It connects independent networks together to form an internetwork. According to this definition, two networks (LANs or WANs) connected by a router become an internetwork or an internet. A three-layer switch is a router

48. ROUTER There are three major differences between a router and a repeater or a bridge. A router has a physical and logical (IP) address for each of its interfaces. A router acts only on those packets in which the physical destination address matches the address of the interface at which the packet arrives. A router changes the physical address of the packet (both source and destination) when it forwards the packet.

49. COMPONENTS The router has four components : Input ports Output ports Routing processor Switching fabric

50. COMPONENTS Input port: An input port performs the physical and data link layer functions of the router. The bits are constructed from the received signal. The packet is decapsulated from the frame. Errors are detected and corrected

51. COMPONENTS Output ports: An output port performs the same functions as the input port, but in the reverse order. First the outgoing packets are queued, then the packet is encapsulated in a frame And finally the physical layer functions are applied to the frame to create the signal to be sent on the line.

52. COMPONENTS Routing processor: The routing processor performs the functions of the network layer . The destination address is used to find the address of the next hop. This activity is sometimes referred to as table lookup because the routing processor searches the routing table.

53. COMPONENTS Switching fabric: The most difficult task in a router is to move the packet from the input queue to the output queue. The speed with which this is done affects the size of the input/output queue and the overall delay in packet delivery. Routers use a variety of switching fabrics. Some of the switching fabrics is , Crossbar Switch Banyan switch

54. Advantages Easily Shared Internet. Security and Adaptability. Router limits the collision domain. Router can function on LAN & WAN. Router can connects different media & architectures.

55. Disadvantages Router is more expensive than Hub, Bridge & Switch. Routing updates consume bandwidth. Increase latency due to greater degree of packet  filtering. Complicated Setup.

56. A typical home / office wired router

57. Example connections on a router

58. Wireless router with USB

59. GATEWAY

60. Gateway is a component that is part of two networks, which use different protocols. It operates at all seven layers of OSI model. Unlike a router a gateway can forward packets across different networks that may also use different protocols. For example, If network A is token ring network using TCP / IP and network B is in a Ethernet network, a gateway can relay frames between these two networks. GATEWAY

61. Application layer Presentation layer Session layer Transport layer Network layer Data link layer Physical layer G A T E W A Y A Physical layer Data link layer Network layer Transport layer Session layer Presentation layer Application layer B Gateway at all OSI layers

62. FUNCTIONS It has abilities to translate between different frame formats and also between different protocols. It is a very powerful computer system compared with bridge. Used to connect huge and incompatible networks.

63. ADVANTAGES The direct linking between internal and external hosts are denied. In network gateway, the user level authentication or protection is supported. Can connect or links two variant networks. The protocol conversion is done and it handles the traffic problems.

64. DISADVANTAGES It is not an intellectual equipment. Protocol conversion is done so transmission rate is slower. Expensive. Little hard to handle. Needs internal client to know about them.

65. References “Data Communications and Networking”, Behrouz A Forouzan . “Computer Networks -A Systems Approach”, Larry L Peterson, Bruce S Davie. http://wikipedia.org/wiki/Networking_devices

66. Thank you