What is packet switching in networking?
The basic technique utilized in contemporary computer networks, such as the entire internet, to effectively transfer digital data is packet switching. Data is separated into smaller units called packets and sent via a network as part of this communication mechanism. By sharing network resources instead of reserving a specific path, this technique gets beyond the drawbacks of previous technologies like circuit switching.
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Packet and Its Structure
A packet is a discrete data unit. A message (such an email or video file) is divided into individual packets when it is sent. Packets are little packages that include delivery directions and information.
Most importantly, each package includes:
- A subset of the data (payload).
- A control information header. This header normally provides the sequence number and reassembly source and destination addresses.
Ethernet Max Transmission Units are 1500 bytes.
How Packet Switching Works
Independent packet mobility and dynamic routing are characteristics of packet switching. The method entails:
- Segmentation: These smaller packets are created by splitting the original message.
- Only the final destination address is known by each data unit in packet switching; routers determine the intermediate pathways.
- The packet switching approach is a store-and-forward method. At every intermediate node, including the source system, data is processed.
- Reassembling: After arriving, the packets are rearranged by sequence number to recreate the message.
- TCP manages reliability by identifying missing packets and requesting retransmission to ensure delivery.
Protocols, such as TCP (Transmission Control Protocol), handle reliability by detecting lost packets and requesting retransmission to ensure complete delivery.
Types of Packet Switching
Packet switching can be divided into two main categories according to how the connection path is managed:
Package switching without a connection (Datagram):
- Every packet receives complete and independent treatment.
- Setting up a connection is not necessary.
- Different routes may be taken by packets, and they may arrive out of order.
- The Internet and other IP networks make advantage of this.
Packet switching based on connections, or virtual circuits:
- Data transfer starts after the sender and receiver have established a logical path (a virtual circuit).
- Every packet travels along this predetermined path, guaranteeing their sequential arrival.
- This method involves setup, data transfer, and teardown.
- X.25, Frame-Relay, ATM, and MPLS use it.
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Advantages of packet switching and Disadvantages
The design prioritized packet switching efficiency and flexibility, notably for erratic data flow.
| Feature | Advantages of Packet Switching | Disadvantages of Packet Switching |
|---|---|---|
| Bandwidth/Cost | Efficient use of bandwidth because resources are shared among multiple users. Bandwidth is used only when data is actively being transmitted. It is generally lower cost than circuit switching. | Overhead is added to the data because each packet requires a header with control information. |
| Reliability/Tolerance | Greater fault tolerance and reliability because packets can be rerouted around failed links or congested areas (network redundancy). | Potential for packet loss due to network congestion or transmission errors. |
| Scalability/Flexibility | Highly scalable and can handle large amounts of traffic and a wide range of data rates. It is flexible enough to handle bilateral traffic. | Increased complexity at nodes, as each intermediate node must be capable of routing packets dynamically. |
| Performance/Order | Minimal transmission latency since data is sent as soon as it is ready. | Higher latency and jitter (inconsistent delays) can occur because packets must be routed through multiple nodes and may take different paths. Packets may arrive out of order. |
| Real-Time | Although it underpins technologies like VoIP and video conferencing, it is considered unsuitable for real-time communication compared to circuit switching because of the potential for latency and packet loss. | Limited Quality of Service (QoS) guarantees, meaning different traffic types may be treated equally. |
Packet Switching Analogy
Packet switching can be thought of as the postal delivery of an enormous book. The process involves tearing out each page (packet), placing it in a separate envelope with the destination address and page number (sequence number), and mailing it instead of keeping a single huge box for the entire trip (which would be similar to circuit switching). Even though the envelopes may arrive via different routes, the recipient successfully reassembles the book upon arrival by using the page numbers.
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