chapter 11 (switching) Moaz Mohamed.pptx

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1. Chapter 11  Switching Moaz mohamed  

2. Ethernet basics is one of the first local area networking (LAN) protocols to be released commercially in 1980,  standard for the network was called Ethernet, but the current standards are published  by the IEEE as part of the 802.3 working group. Therefore, the Ethernet networks being  built today are actually IEEE 802.3 networks.

3. Ethernet frame  The Ethernet frame is the outermost envelope in a packet transmitted over a local area  network. The frame consists of a header and a footer that encapsulate the payload that the   Ethernet protocol receives from the network layer protocol above it, usually Internet Protocol (IP)

4. Ethernet uses  access control (MAC) addresses to identify systems on a LAN. A MAC address is a 6-byte value  A MAC address is a  6-byte value, expressed in hexadecimal notation, as in the following example:  52-E7-AD-C5-96-18 

5. Carrier-Sense Multiple Access with Collision   Detection (CSMA/CD)  In its early iterations, the Ethernet standards called for a shared network medium, such as that on a coaxial bus or a hub-based star network. In a shared network medium, when two hosts transmit at the same time, a packet collision occurs, usually requiring the retransmission of both packets. CSMA/CD defines a method by which hosts can access a shared network medium with a  reduced chance of collisions occurring and detect collisions when they do occur

6. Carrier Sense :-   Before a host transmits, it listens to the network to see if it is in use. If it is in use, the host pauses before listening again  Multiple Access :-  When the network is clear, the host begins transmitting. The transmitted packet fills the entire shared network medium before the host finishes transmitting it. It is during this time that a collision can occur. Collision Detection :-  When the transmitting host detects signals on both its transmit  and receive wires simultaneously, it declares a signal quality error (or collision), stops transmitting data, and starts transmitting a jam signal instead. The jam signal alerts any  other transmitting systems of the collision, causing them to discard any incoming data they have received

7. Physical Layer Specifications There are dozens of specifications supporting different network media, but only a few have  remained in general use.  An Ethernet specification defines the characteristics of the network medium, such as what  category of UTP cable to use, and also provides installation guidance, such as the  maximum  length of a cable segment