What Is Packet Switching on Computer Networks?

what is atm switch

By Bradley Mitchell. Wireless/Networking Expert

Bradley is a computer professional with 20 years experience in network software development, project management, and technical writing. He has covered wireless and computer networking topics for About.com since 1999. See also - Bradley Mitchell at Google+

Packet switching is the 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 .

How Packet Switching Works

Packet switching entails packaging data in specially formatted units (called packets ) that are typically routed from source to destination using network switches and routers .

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.

What Is a Hop?

In computer networking, a hop represents one portion of the full path between source and destination. When communicating over the Internet, for example, data passes through a number of intermediate devices (routers and switches) rather than flowing directly over a single wire.

Each such 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 piece of data (packet) passes through. Generally speaking, the more hops data must traverse to reach their destination, the greater the transmission delay incurred.

Network utilities like 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, incrementing the hop count by one.

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In addition, the device compares the hop count against a predetermined limit and discards the packet if its hop count is too high. This prevents packets from endlessly bouncing around the network due to routing errors.

Pros and Cons of Packet Switching

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

Compared to circuit switching, packet switching offers the following:

  • 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.
  • 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.
  • Source: compnetworking.about.com

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