An Overview of Packet Switching on Computer Networks

Packet switching protocols include IP and X-25

Packet switching is an approach used by some computer network protocols to deliver data across a local or long-distance connection. Examples of packet switching protocols are Frame Relay, IP, and X.25.

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How Packet Switching Works

Packet switching breaks data into several parts that are packaged in specially formatted units called packets. These are typically routed from the source to the destination using network switches and routers. Then the data is reassembled at the destination.

Each packet contains address information that identifies the sending computer and intended recipient. Using these addresses, network switches and routers determine how best to transfer the packet between hops on the path to its destination. There are free apps, such as Wireshark, that capture and view the data if necessary.

What Is a Hop?

In computer networking, a hop represents one portion of the full path between the source and the destination. When communicating over the internet, for example, data passes through a number of intermediate devices, including routers and switches, rather than flowing directly over a single wire. Each device causes data to hop between one point-to-point network connection and another.

The hop count represents the total number of devices a given packet of data passes through. Generally speaking, the more hops that data packets must traverse to reach their destination, the greater the transmission delay incurred.

Network utilities such as ping can be used to determine the hop count to a specific destination. Ping generates packets that include a field reserved for the hop count. Each time a capable device receives these packets, that device modifies the packet and increases the hop count by one. In addition, the device compares the hop count against a predetermined limit and discards the packet if its hop count is too high. This action prevents packets from endlessly bouncing around the network due to routing errors.

Pros and Cons of Packet Switching

Packet switching is the alternative to the circuit switching protocols used historically for telephone networks and sometimes with ISDN connections.

Compared to circuit switching, packet switching offers the following pros and cons:

  • 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.

  • Reliability. If a packet doesn't arrive as expected at its destination, the receiving computer detects one packet is missing and requests for it to be resent.

  • Packet switching offers automatic rerouting should any node on its journey fail.

  • 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 Quality of Service (QoS) technology is often necessary to achieve the required performance levels.

  • The potential for network security risks exists due to the use of shared physical links. Protocols and other related elements in packet switching networks must align with the appropriate security precautions.

  • Latency is unpredictable.

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