Inside Look at the Internet
1.2.2 Connectionless and Connection-Oriented Service
Chapter 1
1.1 What Is the Internet?
1.1.1 Nuts-and-Bolts Description
1.1.2 A Service Description
1.1.3 What Is a Protocol?
1.2 The Network Edge
1.2.1 End Systems, Clients, and Servers
1.2.2 Connectionless and Connection-Oriented Service
1.3 Network Core
1.3.1 Circuit Switching and Packet Switching
1.3.2 Packed-Switched Networks: Datagram Networks and Virtual-Circuit Networks
1.4 Access Networks and Physical Media
1.4.1 Access Networks
1.4.2 Physical Media
1.5 ISPs and Internet Backbones
1.6 Delay and Loss in Packets-Switched Networks
1.6.1 Types of Delay
1.6.2 Queuing Delay and Packet Loss
1.6.3 Delay and Routes in the Internet
1.7 Protocol Layers and Their Service Models
1.7.1 Layered Architecture
1.7.2 Layers, Messages, Segments, Datagrams, and Frames

TCP/IP networks, and in particular the Internet, provide two types of services to end-system applications: connectionless service and connection-oriented service . A developer creating an Internet application must design the application to use one of these two services.

  • Connection-Oriented Service

    The Internet's connection-oriented service comes bundled with several other services, including reliable data transfer, flow control, and congestion control. By reliable data transfer we mean that an application can rely on the connection to deliver all of its data without error and in the proper order. Flow control makes sure that neither side of a connection overwhelms the other side by sending too many packets too fast. The Internet's congestion-control service hellps prevent the INternet from entering a state of gridlock. When a packet switch becomes congested, its buffers can overflow and packet loss can occur. The Internet's connection-oriented service has a name--Transmission Control Protocol (TCP).

  • Connectionless Service

    When one side of an application wants to send packets to the other side of the application, the sending program simply sends the packets. Since there is no handshaking procedure prior to data packet transmission, data can be delivered sooner. This makes connectionless service ideal for simple transaction-oriented applications. But there is no reliable data transfer either, so a source never knows for sure which packets have arrived at the destination. The Internet's connectionless service is called User Datagram Protocol (UDP).