Changes in the standard ppt


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Changes in the standard
Presented by : Malik S.Abeisat

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Changes in the standard ppt

  1. 1. CHAPTER 13 WIRED LANS: ETHERNET 13.3 CHANGES IN THE STANDARD Presented by : Malik S.Abeisat
  2. 2. - From 10-Mbps Standard Ethernet until it’s moving to higher data rate , it passes through through several changes. - These changes actually opened the road to the evolution of the Ethernet to become compatible with other high-data-rate LANs. - Here we’ll talk about some of them : Bridged Ethernet Switched Ethernet Full-Duplex Ethernet 1
  3. 3. Bridged Ethernet 2
  4. 4. WHAT EXACTLY IS A BRIDGE IN NETWORKING? _____________________________________ A Bridge is a device that filters data traffic at a network boundary. Bridges reduce the amount of traffic on a LAN by dividing it into two segments. It connects on the data-link layer, (layer 2) of the OSI model. In the picture to the right, the data is coming from the database server. The bridge filters the data, sending the data to the correct locations. 3
  5. 5. BRIDGED ETHERNET  The first step in the Ethernet evolution was the division of a LAN by bridges.  The term bridge was coined in the early 1980s.  Today, the terms LAN switch or (in the context of Ethernet) Ethernet switch are used.  Bridges have two effects on an Ethernet LAN: 1- They raise the bandwidth. 2- they separate collision domains.    Bridges are intermediate systems that forward MAC frames to destinations based on MAC addresses. Q. Is an Ethernet hub a bridge or a repeater ? What’s the difference ? A. It can be either a bridge or a repeater. “hub” is a product name, not an architecture name. Modern hubs are bridges. Old ones are repeaters.The difference is: a repeater is a layer 1 intermediate system (acts on bits) whereas a bridge is a layer 2 intermediate system (acts on entire MAC frames). Also: a bridge separates collision domains, a repeater does not hub hub hub 4
  6. 6. HOW DOES A BRIDGE WORK? ___________________________ Bridges are similar to repeaters and network hubs, devices that connect at the physical layer, however, with bridging, traffic from one network is managed rather than simply rebroadcast to adjacent network segments. Bridges tend to be more complex than hubs or repeaters. Bridges can analyze incoming data packets to determine if the bridge is able to send the given packet to another segment of the network. Since bridging takes place at the data-link layer of the OSI model, a bridge processes the information from each frame of data it receives. In an Ethernet frame, this provides the MAC address of the frame's source and destination. Bridges use two methods to resolve the network segment that a MAC address belongs to. 5
  7. 7. Bridged Ethernet_Effect 1. Raising the Bandwidth Stations shares the total bandwidth they are provided with. When we have more than one station they share the provided bandwidth hence we can put the bridge we can spilt the stations so that they can share the same bandwidth but the number of stations are less as it’s divided between stations. For example, We have 10 stations sharing 10 mbps now if we bridge them over 5-5 stations ,we will have 5 stations sharing the same 10mbps bandwidth, hence bridged connection can increase the bandwidth by above mentioned method. 6
  8. 8. 2. Separating Collision Domains The collision domain becomes much smaller and the probability of collision is reduced tremendously. Without bridging, 12 stations contend for access to the medium; with bridging only 3 stations contend for access to the medium. 7
  9. 9. Switched Ethernet 8
  10. 10. SWITCHED ETHERNET  Consists of a several segments, each of which is shared by NICs attached to it. (Network interface controller “NIC”) The network is segmented into several collision domains.  Bridges, switches, and routers create the segment and collision domain boundaries.  Segments may contain hubs and repeaters. There is switch table and it’s build by (media access control address “MAC”) for each device  9
  11. 11. SWITCHED ETHERNET Switch - 1 port per hub Hub Hub 10
  12. 12. 11
  13. 13. Full-Duplex Ethernet 12
  14. 14. Full-duplex is a data communications term that refers to the ability to send and receive data at the same time.  The full-duplex mode increases the capacity of each domain (ex. from 10 to 20 Mbps).  instead of using one link between the station and the switch, the configuration uses two links: one to transmit and one to receive.  13
  15. 15.  In full-duplex mode, both devices can transmit and receive to and from each other at the same time, and there is no collision domain. This doubles the aggregate bandwidth of the link and is sometimes advertised as double the link speed (e.g., 200 Mbit/s). o The elimination of the collision domain for these connections also means that all the link's bandwidth can be used by the two devices on that segment and that segment length is not limited by the need for correct collision detection. 14
  16. 16. No Need for (CSMA/CD) 15
  17. 17. (CSMA/CD) Carrier Sense Multiple Access With Collision Detection  Collision: two transmissions interfere with each other  Station that wants to transmit first listens to check if another transmission is in progress (carrier sense).  If medium is in use, station waits; else, it transmits.  Collisions can still occur.  Transmitter waits for ACK; if no ACKs, retransmits. 16
  18. 18. ETHERNET: CSMA/CD (CARRIER SENSE MULTIPLE ACCESS WITH COLLISION DETECTION)  Access method: method of controlling how network nodes access communications channels  CSMA/CD: Ethernet’s access method  Ethernet NICs listen on network Wait until no nodes transmitting data over the signal on the communications channel before transmission  Several Ethernet nodes can be connected to a network and can monitor traffic simultaneously  17 (Network interface controller “NIC”)
  19. 19. In a full-duplex switched Ethernet, each station is connected to the switch via two separate links.  Each station or switch can send and receive independently without worrying about collision.  Each link is a point-to-point dedicated path between the station and the switch.  There is no longer a need for carrier sensing; there is no longer a need for collision detection. The job of the MAC layer becomes much easier.  The carrier sensing and collision detection functionalities of the MAC sublayer can be turned off.  18
  20. 20. MAC Control Layer 19
  21. 21. DEFINITION MAC    Specified by the technology being used. Determine who can transmit and when. Two types:  Deterministic: “Let’s take turns”.   Token-Ring, FDDI. Non-deterministic: “First come, first serve”.  Ethernet : CSMA/CD. 20
  23. 23. NON-DETERMINISTIC MAC PROTOCOL  Carrier Sense Multiple Access with Collision Detection (CSMA/CD). 22
  24. 24. USING MAC ADDRESSES Data A D Data A D Destination Address Source Address Data A D Data A D 23
  25. 25. Thanks on your attentions Best regards Presented by : Malik S.Abeisat