7 topology ethernet

topologies

1. Network topology

2. Topology Topology refers to the layout of connected devices on a network. Here, some logical layout of topology. Mesh Star Bus Ring Tree and Hybrid

3. Network Topology

4. Mesh Topology Here every device has a point to point link to every other device. Node 1 node must be connected with n-1 nodes. A fully connected mesh can have n(n-1)/2 physical channels to link n devices. It must have n-1 I/O ports.

5. Mesh Topology Advantages: They use dedicated links so each link can only carry its own data load. So traffic problem can be avoided. It is robust. If any one link get damaged it cannot affect others. It gives privacy and security.(Message travels along a dedicated link) Fault identification and fault isolation are easy.

6. Mesh Topology

7. Mesh Topology

8. Mesh Topology Disadvantages: The amount of cabling and the number of I/O ports required are very large. Since every device is connected to each devices through dedicated links. The bulk of wiring is larger then the available space. Hardware required to connected each device is highly expensive.

9. Mesh Topology Applications: Telephone Regional office. WAN.(Wide Area Network).

10. Star Topology Here each device has a dedicated point-to-point link to the central controller called “Hub”(Act as a Exchange) . There is no direct traffic between devices. The transmission are occurred only through the central “hub”. When device 1 wants to send data to device 2; First sends the data to hub. Which then relays the data to the other connected device.

11. Star Topology

12. Star Topology

13. Star Topology Advantages: Less expensive then mesh since each device is connected only to the hub. Installation and configuration are easy. Less cabling is need then mesh. Robustness.(if one link fails, only that links is affected. All other links remain active) Easy to fault identification & to remove parts. No distruptions to the network then connecting(or) removing devices.

14. Star Topology Disadvantages: Even it requires less cabling then mesh when compared with other topologies it still large.(Ring or bus). Dependency(whole n/w dependent on one single point(hub). When it goes down. The whole system is dead.

15. Applications Star topology used in Local Area Networks(LANs). High speed LAN often used STAR.

16. Asynchronous Transfer Mode (ATM ) example of star topology

17. Asynchronous Transfer Mode By the mid 1980s, three types of communication networks had evolved. The telephone network carries voice calls, television network carries video transmissions, and newly emerging computer network carries data. Telephone companies realized that voice communication was becoming a commodity service and that the profit margin would decrease over time. They realized that data communication was increasing. The telecommunication industry decided to expand its business by developing networks to carry traffic other than voice.

18. Asynchronous Transfer Mode (ATM) is a switching technique for telecommunication networks. It uses asynchronous  time-division multiplexing , [1][2 ]  and it encodes data into small, fixed-sized  cells . ATM differs from networks such as the  Internet  or  Ethernet LANs  that use variable sized  packets  or  frames .  ATM provides  data link layer  services that run over  OSI   Layer 1  physical links. ATM has functional similarity with both  circuit  switched networking and small packet switched networking. This makes it a good choice for a network that must handle both traditional high-speed data traffic (e.g., file transfers), and  real-time ,  low-latency  content such as voice and video . Asynchronous Transfer Mode

19. ATM ATM standard is widely accepted by common carriers as mode of operation for communication – particularly BISDN. ATM is a form of cell switching using small fixed-sized packets. Header Payload 5 Bytes 48 Bytes Figure 9.1 Basic ATM Cell Format Leon-Garcia & Widjaja: Communication Networks Copyright ©2000 The McGraw Hill Companies

20. ATM is more complex, but this complexity allows to give guarantees as to  data rate , maximum delay, and  jitter . These are usually called  Quality of Service . JITTER : In voice over IP ( VoIP ), jitter is the variation in the time between packet s arriving, caused by network congestion, timing drift, or route changes. A jitter buffer can be used to handle jitter. Jitter is the deviation in or displacement of some aspect of the pulses in a high-frequency digital signal .   Quality of Service  or QoS is a method of providing better service for selected traffic types over various types of packet-switched networks.

21. Advantages Universality Mixed traffic types, real-time and non-real-time Scalability LANs, MANs, WANs, WLANs Efficient use of network resources Bandwidth on demand concept Simplified network infrastructure

22. Disadvantages ATM has not been widely accepted. Although some phone companies still use it in their backbone networks. The expense, complexity and lack of interoperability with other technologies have prevented ATM from becoming more prevalent.

23. Disadvantages Complexity of QoS : The complexity of the specification makes implementation cumbersome and difficult. Many implementations do not support the full standard. Assumption of Homogeneity: ATM is designed to be a single, universal networking system. There is minimal provision for interoperating with other technologies

24. Bus Topology A bus topology is multipoint. Here one long cable act as a backbone to link all the devices are connected to the backbone by drop lines and taps. Drop line- is the connection b/w the devices and the cable. Tap- is the splitter that cut the main link.  This allows only one device to transmit at a time .

25. Bus Topology

26. Bus Topology

27. Bus Topology

28. Bus Topology

29. Bus Topology A device want to communicate with other device on the n/ ws sends a broadcast message onto the wire all other devices see. But only the intended devices accepts and process the message.

30. Bus Topology Advantages : Ease of installation Less cabling Disadvantages: Difficult reconfiguration and fault isolation. Difficult to add new devices. Signal reflection at top can degradation in quality. If any fault in backbone can stops all transmission.

31. Bus Topology Applications: Most computer motherboard .

32. Ring Topology Here each device has a dedicated connection with two devices on either side. The signal is passed in one direction from device to device until it reaches the destination and each device have repeater . When one device received signals instead of intended another device, its repeater then regenerates the data and passes them along. To add or delete a device requires changing only two connections.

33. Ring Topology

34. Ring Topology

35. Ring Topology

36. Ring Topology Advantages : Easy to install. Easy to reconfigure. Fault identification is easy. Disadvantages: Unidirectional traffic. Break in a single ring can break entire network.

37. Ring Topology Applications: Ring topologies are found in some office buildings or school campuses . Today high speed LANs made this topology less popular. EX… IBM Token Ring,FDDI

38. IBM Token Ring IBM created IEEE( Institute of Electrical and Electronics Engineers ) 802.5 standard known as Token Ring it uses a special packet known as Token Multi-station Access Unit (MSAU)

39. A Token Ring network is a local area network (LAN) in which all computers are connected in a ring or star topology and a bit - or token-passing scheme is used in order to prevent the collision of data between two computers that want to send messages at the same time. The Token Ring protocol is the second most widely-used protocol on local area networks after Ethernet . The IBM Token Ring protocol led to a standard version, specified as IEEE 802.5. Both protocols are used and are very similar. The IEEE 802.5 Token Ring technology provides for data transfer rates of either 4 or 16 megabits per second.

40. FDDI (Fiber Distributed Data Interface) FDDI is a standard developed by the American National Standards Institute (ANSI) for transmitting data on optical fibers Supports transmission rates of up to 200 Mbps Uses a dual ring First ring used to carry data at 100 Mbps Second ring used for primary backup in case first ring fails If no backup is needed, second ring can also carry data, increasing the data rate up to 200 Mbps Supports up to 1000 nodes Has a range of up to 200 km The possessor of the token is allowed to put a new token onto the ring as soon as it finished transmitting its frames

41. Tree Topology Alternatively referred to as a star bus topology. Tree topology is one of the most common network setups that is similar to a bus topology and a star topology. A tree topology connects multiple star networks to other star networks. Below is a visual example of a simple computer setup on a network using the star topology.

42. Tree Topology

43. Hybrid Topology A network which contain all type of physical structure and connected under a single backbone channel.

44. Hybrid Topology a

45. Considerations for choosing topology Money -Bus n/w may be the least expensive way to install a n/w. Length - of cable needed- the linear bus n/w uses shorter lengths of cable. Future growth -with star topology, expending a n/w is easily done by adding another devices. Cable type -most common used cable in commercial organization is twisted pair. Which often used with star topologies.

46. Full mesh topology is theoretically the best since every device is connected to every other device.(thus maximizing speed and security. however, it quite expensive to install) Next best would be tree topology , which is basically a connection of star.

47. Ethernet 1973 by Bob Metacalfe (IEEE standard called 802.3 CSMA/CD)

48. Ethernet Overview Most popular packet-switched LAN technology Bandwidths: 10Mbps , 100Mbps , 1Gbps Max bus length: 2500m 500m segments with 4 repeaters Bus and Star topologies are used to connect hosts Hosts attach to network via Ethernet transceiver or hub or switch Detects line state and sends/receives signals Hubs are used to facilitate shared connections All hosts on an Ethernet are competing for access to the medium Switches break this model Problem: Distributed algorithm that provides fair access

49. Ethernet by definition is a broadcast protocol Any signal can be received by all hosts Switching enables individual hosts to communicate Network layer packets are transmitted over an Ethernet by encapsulating Frame Format Dest addr 64 48 32 CRC Preamble Src addr Type Body 16 48

50. Collision Domain a section of a network where data packets can collide with one another when being sent on a shared medium the larger the collision domain, the more likely it is that collision will occur

51. CSMA/CD Carrier Sense Multiple Access/Collision Detect ( CSMA /CD) is the protocol for carrier transmission access in Ethernet networks. On Ethernet, any device can try to send a frame at any time. Each device senses whether the line is idle and therefore available to be used. If it is, the device begins to transmit its first frame. If another device has tried to send at the same time, a collision is said to occur and the frames are discarded. Each device then waits a random amount of time and retries until successful in getting its transmission sent.

52. Intranet Intranet is system in which multiple PCs are connected to each other. PCs in intranet are not available to the world outside the intranet. Usually each company or organization has their own Intranet network and members/employees of that company can access the computers in their intranet. Each computer in Intranet is also identified by an IP Address which is unique among the computers in that Intranet. Intranet (HCL) Intranet (Wipro) Internet Extranet