Packet-switching
- Definitions: Packet-switched networks move data in separate, small blocks -- packets -- based on the destination address in each packet. When received, packets are reassembled in the proper sequence to make up the message.
- Packet Switching : A digital networking communications method that groups all transmitted data – regardless of content, type, or structure – into suitably sized blocks, called packet.
- In packet-switching, the packets are sent towards the destination irrespective of each other. Each packet has to find its own route to the destination. There is no predetermined path; the decision as to which node to hop to in the next step is taken only when a node is reached. Each packet finds its way using the information it carries, such as the source and destination IP addresses.
- If a packet switch does not have enough resources, it sends a Connect Reject and the Connection Establishment Fails.
- In packet switching, information is broken into small segments of data known as packets and then reassembled when received at the destination.
- A packet switched network establishes a path from host to host over a shared medium, i.e. the boys in this story. Packet switching relies on shared resources to transfer data across the network, similar to yelling across a field where multiple conversations are going on at the same time. They have to share the resources.
- This helps prevent any small information sent after larger information from having to wait until the larger information has been sent.
- When information is broken into packets, the information size and speed of the line is what determines how fast it takes to send information over a network and not the order in which it was sent.
Advantage of Packet Switching:
- More efficient use of overall network bandwidth due to flexibility in routing the smaller packets over shared links. Packet switching networks are often cheaper to build as less equipment is needed given this ability to share.
- Another benefit of packet switching is known as “pipelining”.
Disadvantage of Packet Switching:
- Longer delays in receiving messages due to the time required to package and route packets. For many applications, delays are not long enough to be significant, but for high-performance applications like real-time video, additional data compression and QoS technology is often required to achieve the required performance levels.
- Potential for network security risks due to the use of shared physical links. Protocols and other related elements on packet switching networks must designed with the appropriate security precautions.
Circuit Switching
- Definitions: Circuit-switched networks require dedicated point-to point connections during calls.
- Circuit Switching : Circuit-switched is a type of network in which a physical path is obtained for and dedicated to a single connection between two end-points in the network for the duration of the connection.
- Ordinary voice phone service is circuit-switched. The telephone company reserves a specific physical path to the number you are calling for the duration of your call.
- During that time, no one else can use the physical lines involved.Traditional PSTN phone system uses circuit switching while VoIP uses packet switching.
- Designed in 1878, circuit-switched networks reserve a dedicated channel for the entire communication.
- The primary hardware for a circuit-switched network is the private branch exchange (PBX) system. Computer servers power packet-switched networks.
- In modern circuit-switched networks, electronic signals pass through several switches before a connection is established. And during a call, no other network traffic can use those switches.
- A circuit switched network is greedier with its resources but ensures the availability of those resources. Similar to the girls in the story, circuit switching establishes a path by reserving circuits along the way.
- From point A to point B you have allocated specific resources for the duration of the conversation. Host A and Client B have sole rights to leverage those resources until terminating the call.
- In the past circuit switching technologies existed mostly for voice communications. In today’s day and age, voice traffic is also sharing the road with data networks in a converged packet switched environment.
- In the above example, before packet switching if the information you wanted to send and you were number five in the list you would have to wait for 1, 2, 3, and 4 to complete before any of your information would be sent.
- However, with packet switching each segment of information is broken into packets, so with a small amount of information you only needed to wait a short amount of time.
- In the above example, it would take the number one much longer to complete because it is bigger, which means it is broken into many more packets.
More About
Difference Between Packet and Circuit
Switching :
Packet Switching
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Circuit Switching
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Variable rate data stream(packed) over a shared connection
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Constant rate data stream(packed) over some dedicated
connection
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characterized by a fee per unit of information.
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characterized by a fee per time unit of connection time, even
when no data is transferred
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Low reliable , subject to congestion
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Highly reliable
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