1.2 Types of Packet-Switched Networks | Introduction to Packet-Switched Networks (2023)

This chapter is from the book 

This chapter is from the book

Computer and Communication Networks, 2nd Edition

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This chapter is from the book

This chapter is from the book 

Computer and Communication Networks, 2nd Edition

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1.2 Types of Packet-Switched Networks

Packet-switched networks are classified as connectionless networks and connection-oriented networks, depending on the technique used for transferring information. The simplest form of a network service is based on the connectionless protocol that does not require a call setup prior to transmission of packets. A related, though more complex, service is the connection-oriented protocol in which packets are transferred through an established virtual circuit between a source and a destination.

1.2.1 Connectionless Networks

Connectionless networks, or datagram networks, achieve high throughput at the cost of additional queuing delay. In this networking approach, a large piece of data is normally fragmented into smaller pieces, and then each piece of data is encapsulated into a certain “formatted” header, resulting in the basic Internet transmission packet, or datagram. We interchangeably use packets and datagrams for connectionless networks. Packets from a source are routed independently of one another. In this type of network, a user can transmit a packet anytime, without notifying the network layer. A packet is then sent over the network, with each router receiving the packet forwarding it to the best router it knows, until the packet reaches the destination.

The connectionless networking approach does not require a call setup to transfer packets, but it has error-detection capability. The main advantage of this scheme is its capability to route packets through an alternative path in case a fault is present on the desired transmission link. On the flip side, since packets belonging to the same source may be routed independently over different paths, the packets may arrive out of sequence; in such a case, the misordered packets are resequenced and delivered to the destination.

Figure 1.6 (a) shows the routing of three packets, packets 1, 2, and 3, in a connectionless network from point A to point B. The packets traverse the intermediate nodes in a store-and-forward fashion, whereby packets are received and stored at a node on a route; when the desired output port of the node is free for that packet, the output is forwarded to its next node. In other words, on receipt of a packet at a node, the packet must wait in a queue for its turn to be transmitted. Nevertheless, packet loss may still occur if a node’s buffer becomes full. The node determines the next hop read from the packet header. In this figure, the first two packets are moving along the path A, D, C, and B, whereas the third packet moves on a separate path, owing to congestion on path A–D.

Figure 1.6 Two models of packet-switched networks: (a) a connectionless network and (b) a connection-oriented network

The delay model of the first three packets discussed earlier is shown in Figure 1.7. The total transmission delay for a message three packets long traversing from the source node A to the destination node B can be approximately determined. Let tp be the propagation delay between each of the two nodes, tf be the time it takes to inject a packet onto a link, and tr be the total processing delay for all packets at each node. A packet is processed once it is received at a node. The total transmission delay, Dp for nb nodes and np packets, in general is

Figure 1.7 Signaling delay in a connectionless network

Click to view larger image

In this equation, tr includes a certain crucial delay component, primarily known as the packet-queueing delay plus some delay due to route finding for it. At this point, we focus only on tp and tf, assume tr is known or given, and will discuss the queueing delay and all components of tr in later chapters, especially in Chapter 11.

Example. Figure 1.7 shows a timing diagram for the transmission of three (instead of two) packets on path A, D, C, B in Figure 1.6 (a). Determine the total delay for transferring these three packets from node A to node B.

Solution. Assume that the first packet is transmitted from the source, node A, to the next hop, node D. The total delay for this transfer is tp + tf + tr. Next, the packet is similarly transferred from node D to the next node to ultimately reach node B. The delay for each of these jumps is also tp + tf + tr. However, when all three packets are released from node A, multiple and simultaneous transmissions of packets become possible. This means, for example, while packet 2 is being processed at node A, packet 3 is processed at node D. Figure 1.7 clearly shows this parallel processing of packets. Thus, the total delay for all three packets to traverse the source and destination via two intermediate nodes is Dp = 3tp + 5tf + 4tr.

Connectionless networks demonstrate the efficiency of transmitting a large message as a whole, especially in noisy environments, where the error rate is high. It is obvious that the large message should be split into packets. Doing so also helps reduce the maximum delay imposed by a single packet on other packets. In fact, this realization resulted in the advent of connectionless packet switching.

1.2.2 Connection-Oriented Networks

In connection-oriented networks, or virtual-circuit networks, a route setup between a source and a destination is required prior to data transfer, as in the case of conventional telephone networks. In this networking scheme, once a connection or a path is initially set up, network resources are reserved for the communication duration, and all packets belonging to the same source are routed over the established connection. After the communication between a source and a destination is finished, the connection is terminated using a connection-termination procedure. During the call setup, the network can offer a selection of options, such as best-effort service, reliable service, guaranteed delay service, and guaranteed bandwidth service, as explained in various sections of upcoming chapters.

Figure 1.6 (b) shows a connection-oriented - network. The connection set-up procedure shown in this figure requires three packets to move along path A, D, C, and B with a prior connection establishment. During the connection set-up process, a virtual path is dedicated, and the forwarding routing tables are updated at each node in the route. Figure 1.6 (b) also shows acknowledgement packets in connection-oriented networks initiated from destination node B to source node A to acknowledge the receipt of previously sent packets to source node. The acknowledgement mechanism is not typically used in connectionless networks. Connection-oriented packet switching typically reserves the network resources, such as the buffer capacity and the link bandwidth, to provide guaranteed quality of service and delay. The main disadvantage in connection-oriented packet-switched networks is that in case of a link or switch failure, the call set-up process has to be repeated for all the affected routes. Also, each switch needs to store information about all the flows routed through the switch.

The total delay in transmitting a packet in connection-oriented packet switching is the sum of the connection set-up time and the data-transfer time. The data-transfer time is the same as the delay obtained in connectionless packet switching. Figure 1.8 shows the overall delay for the three packets presented in the previous example. The transmission of the three packets starts with connection request packets and then connection accept packets. At this point, a circuit is established, and a partial path bandwidth is reserved for this connection. Then, the three packets are transmitted. At the end, a connection release packet clears and removes the established path.

Figure 1.8 Signaling delay in a connection-oriented packet-switched network

The estimation of total delay time, Dt, to transmit np packets is similar to the one presented for connectionless networks. For connection-oriented networks, the total time consists of two components: Dp, which represents the time to transmit packets, and Dc, which represents the time for the control packets. The control packets’ time includes the transmission delay for the connection request packet, the connection accept packet, and the connection release packet:

Click to view larger image

Another feature, called cut-through switching, can significantly reduce the delay. In this scheme, the packet is forwarded to the next hop as soon as the header is received and the destination is parsed. We see that the delay is reduced to the aggregate of the propagation times for each hop and the transfer time of one hop. This scheme is used in applications in which retransmissions are not necessary. Optical fiber transmission has a very low loss rate and hence uses cut-through switching to reduce the delay in transmitting a packet. We will further explain the concept of cut-through switching and its associated devices in Chapters 2 and 12.


What are the types of packet-switched networks? ›

Packet-switched networks are classified as connectionless networks and connection-oriented networks, depending on the technique used for transferring information. The simplest form of a network service is based on the connectionless protocol that does not require a call setup prior to transmission of packets.

What is a packet-switched network? ›

Data communications network in which data is divided into small segments known as packets. These are divided so that each packet forms part of a complete message that can be routed through a network of switches to its destination independently of all other packets forming the same message.

What is packet switching quizlet? ›

Packet Switching. divides a message into several packets that can be routed independently to their destination. UDP( User Datagram Protocol) Faster than TCP but does not perform error check or reorder packets if they are out of order.

What are the 3 phases of packet switching? ›

However, packet switching does not need special steps or stages before one can send data across. The three phases in the circuit switching protocol include the connection establishment phase, the actual data transfer phase, and the connection termination phase.

How many types of switched networks are there? ›

This article briefly introduces five types of switches in networking: LAN switch, unmanaged switch, managed switch, PoE switch and stackable switch. All of them have their own characteristics and are used in different network deployment.

What are two examples of packet-switched networks? ›

Packet switching may be classified into connectionless packet switching, also known as datagram switching, and connection-oriented packet switching, also known as virtual circuit switching. Examples of connectionless systems are Ethernet, Internet Protocol (IP), and the User Datagram Protocol (UDP).

What are two types of network switches? ›

Some of the different types of network switches include managed, modular, unmanaged and stackable.

What are two common types of switched networks? ›

Here are some of the most common types of network switches, with more info on each below:
  • KVM Switch.
  • Managed Switch.
  • Unmanaged Switch.
  • Smart Switch.
  • PoE Switch.
Mar 11, 2021

Why is packet switching used? ›

Advantages of packet switching over circuit switching:

Data packets are able to find the destination without the use of a dedicated channel. Reduces lost data packets because packet switching allows for resending of packets. More cost-effective since there is no need for a dedicated channel for voice or data traffic.

What is packet in networking with example? ›

In networking, a packet is a small segment of a larger message. Data sent over computer networks*, such as the Internet, is divided into packets. These packets are then recombined by the computer or device that receives them.

Is Ethernet a packet switched network? ›

Ethernet has always used packet switching. Packet switching works by multiplexing a physical connection on a packet basis. Each packet (or frame on the data link layer) is atomic but consecutive frames can come from or go to completely different sources or destinations (MAC addresses).

What are packet switching methods? ›

Packet switching is a method of data transmission whereby the data is divided in packets. Each packet is given a header containing information of the destination. Each packet is forwarded separately over the network via the most optimum route to the destination using the header information.

Is a router a packet switching? ›

Each router examines and sends each IP packet individually — this is called packet switching. If the network changes, due to congestion or faults, routers can use an alternative interfaces to reach a destination.

What is packet forwarding vs switching? ›

Forwarding is the process of collecting data from one device and sending it to another device. Switching involves collecting data from one device and sending it to multiple devices based on the MAC address of the packets.

What are the 4 major components of packet switch? ›

A packet switch has four components: input ports, output ports, the routing processor, and the switching fabric.

What are the 3 sections of a packet? ›

A network packet is divided into three parts; the header, payload, and trailer, each containing values that are characteristic of it.

What is the best example of packet switching? ›

The Internet is a prime example of a packet-switched network based on the TCP/IP protocol suite. A series of routers located at various points on the Internet's backbone forward each packet received on the basis of destination address until the packet reaches its ultimate destination.

What are the 4 types of switches? ›

Learn the Different Types of Switches
  • Pushbutton Switches. Pushbutton switches are two-position devices actuated with a button that is pressed and released. ...
  • Selector Switches. ...
  • Joystick Switches. ...
  • Limit Switches. ...
  • Proximity Switches. ...
  • Speed Switches. ...
  • Pressure Switches. ...
  • Temperature Switches.

What are the 4 types of networks? ›

There are four types of wireless networks -- wireless local area networks, wireless metropolitan area networks, wireless personal area networks and wireless wide area networks -- each with its own function.

What are the three switching methods? ›

There're three main switching techniques used in computer networks: circuit switching, packet switching, and message switching. Let's discuss them comprehensively.

What is an example of packet switching network? ›

Packet switching is the method by which the internet works, it features delivery of packets of data between devices over a shared network. For example the school web server sending you a webpage over the internet or you sending an email to a friend.

What are examples of switched networks? ›

An example of a circuit-switched network is an analog telephone network. It contrasts with packet-switched networks, which break the communication into packets and then send those packets through the network independently of one another.

What are the different types of packet protocol? ›

You can choose from four basic Internet packet protocols: raw IP, ICMP, UDP (unreliable messaging), and TCP (streaming) all layered on top of the physical network (see Figure 3.1). This chapter describes each type and presents their advantages, disadvantages, and typical uses.

What are the 4 types of delay in packet-switched network? ›

In packet switched networks, there are four types of commonly identified delays – processing, queuing, transmission and propagation delays. Processing delay is the CPU cycles needed to look at the packet headers and decide what to do with the packet, and do it – basically the time needed to process the packet.

What are the two 2 main types of networks? ›

Two basic network types are local-area networks (LANs) and wide-area networks (WANs).

What are different types of switches? ›

Learn the Different Types of Switches
  • Pushbutton Switches. Pushbutton switches are two-position devices actuated with a button that is pressed and released. ...
  • Selector Switches. ...
  • Joystick Switches. ...
  • Limit Switches. ...
  • Proximity Switches. ...
  • Speed Switches. ...
  • Pressure Switches. ...
  • Temperature Switches.

What are two types of networks ____? ›

Two very common types of networks include:
  • Local Area Network (LAN)
  • Wide Area Network (WAN)


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