What is a Switch in Networking

What is a Switch in Networking networkingguruji1.blogspot.com/2019/07/what-is-switch-in-networking.html

Switch Introduction...

'What is a Switch in Networking' Switching is an approach of delivery frams (Layer 2) across the network.Switching method decided how are switch received, process and forward frams. Switch support switching method.

1) Store -forward 2) Cut - Through 3) Fragment - Through

What is Switch.

A switch, in the context of networking is a high-speed device that receives incoming data packets and redirects them to their destination on a local area network (LAN). A LAN switch operates at the data link layer (Layer 2) or the network layer of the OSI Model and, as such it can support all types of packet protocols.

Switch Explains.

A switch in an Ethernet-based LAN reads incoming TCP/IP data packets/frames containing destination information as they pass into one or more input ports. The destination information in the packets is used to determine which output ports will be used to send the data on to its intended destination.

Switches are similar to hubs, only smarter. A hub simply connects all the nodes on the network -- communication is essentially in a haphazard manner with any device trying to communicate at any time, resulting in many collisions. A switch, on the other hand, creates an electronic tunnel between source and destination ports for a split second that no other traffic can enter. This results in communication without collisions.

Switches are similar to routers as well, but a router has the additional ability to forward packets between different networks, whereas a switch is limited to node-to-node communication on the same network.

switches in networking.

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Layer 2 Switch Introduction....(The Data-Link Layer) .....

Layer 2 switches operate using the data link (MAC) layer addresses. Link-layer, hardware, or MAC-layer addresses identify individual devices. Most hardware devices are permanently assigned this number during the manufacturing process. Switches operating at Layer 2 are very fast because they’re just sorting MAC addresses, but they do not look at the Layer 3 portion of the packet to learn anything more.

Layer 3 Switch Introduction....(The Network Layer) Layer 3 switches use network or IP addresses that identify locations on the network. A location can be a LAN workstation, a location in a computer’s memory, or even a different packet of data traveling through a network. Switches operating at Layer 3 take more time examining packets than Layer 2 devices and incorporate routing functions to actively calculate the best way to send a packet to its destination.

Hub and repetor works at Layer 1 (Physical Layer) . This Device only understand the signal .Signal received on in coming port are forwarded to all available port .

Bridge and switch works are layer 2 (Data link layer). Bridge and switch both are capable to related frames.Switching is a method of dealing with frames.Switch is the upgrade version Bridge.

Switch Bandwidth.

Bandwidth is the data transport (in data unit such as Kb,Mb,GB) through the media in particular time unit such as send.It is a measurement bit rate of available or consume data communication resources express in bit per second or multiple of it. Bandwidth is limited by media type technology. In wan, bandwidth is the costly resources.

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Bandwidth and Delay.....

-Network performance is measured in Bandwidth (throughput) and Latency (Delay).

- Bandwidth of a network is given by the number of bits that can be transmitted over the network in a certain period of time.

- Latency (Delay) corresponds to how long it takes a message to travel from one end off a network to the other. It is strictly measured in terms of time.

Collision Domain.....

A collision domain is a physical network segment where data packets can "collide" with one another for being sent on a shared medium. This is an Ethernet term used to describe a network scenario wherein one particular device sends a packet on a network segment, forcing every other device on that same segment to pay attention to it.

The basic strategy.....

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A computer listens on the cable to see if another computer is transmitting, which is indicated by a voltage change on the cable. If busy, the computer waits and listens.When the cable is not busy, a computer attempts to transmit.Another computer may attempt to transmit at the same time, which causes a collision.Both computers that attempted to transmit must back off, wait a random period of time, and then attempt to transmit again.Layer 2 devices segment or divide collision domains. They use the MAC address assigned to every Ethernet device to control frame propagation. Layer 2 devices are bridges and switches. They keep track of the MAC addresses and their segments. This allows these devices to control the flow of traffic at the Layer 2 level. This function makes networks more efficient. It allows data to be transmitted on different segments of the LAN at the same time without collisions.

CSMA/CD..

- Carrier Sense Multiple Access Collision Detection - CSMA/CD is set of rules, says how to talk on an Ethernet Network + Carrier

– It is Network Signal

+ Sense

– The Ability to Detect Signal

+ Multiple Access – All Devices have Equal Access + Collision – What Happens if Two Devices Sends at Once + Detection – How the Computers Handles Collision When they happen.

Layer 2 Ethernet frame (packet) sizes The Layer 2 Ethernet frame (packet) as described here includes Ethernet headers, i.e. the CRC, but not the Inter Frame Gap, Preamble, or Start of Frame Delimiter (SFD).

The maximum frame size depends on the interface MTU (Maximum Transmission Unit); the default value is 1500 bytes.

The minimum frame size for IPv4 is 64 bytes, where the Ethernet header takes up 18 4/6

bytes, the IPv4 header 20 bytes, and the UDP header 8 bytes. The remaining 18 bytes are payload, where Netrounds places a sequence number, a timestamp, a checksum, and a stream ID. Minimum IPv4 packet size = 18 (Ethernet) + 20 (IPv4) + 8 (UDP) + 18 (payload) = 64 bytes

For IPv6 the minimum frame size is 84 bytes, since the IPv6 header is 40 bytes long.

Layer 2 Header FCS Vs CRC The FCS field contains the data used to verify accurate delivery of frames. CRC is the method (algorithm) performed on that data to do the verification.

CRC-checksums are calculated and that it's easier performed by hardware if the 5/6

structure of a frame is header+payload+crc rather than header+crc+payload.

Layer 3 Header ipv4 Header Format

Full article What is a Switch in Networking Thank you for the full article.

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