What is Connection-Oriented Communication?

This blog post briefly definies Connection-Oriented Communication.

An Example of Connection-Oriented Communication - the Phone Call

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In Computer Networking (and the Internet in general), all communication systems will be one of the two following types:

In this blog post, we will talk about Connection-Oriented Communication; we will speak about Connectionless Communication in another blog post.

The Main Definition of Connection-Oriented Communication

The primary definition of Connection-Oriented Communication is that we must establish an end-to-end connection from Point A to Point B before communication can flow between Points A and B.

I show this requirement below in Figure 1.

In Connection-Oriented Communication, a End-to-End Connection must be established before Communication can begin.

Figure 1, An End-to-End Connection between Points A and B must be set up first.

Characteristics of Connection-Oriented Communication

  • Requires a Setup Phase or Procedure (before any communication can begin).
  • Data arrives (at the Destination) in the same order as it was sent (from the Source).
  • All data blocks (or packets) follow the same path from the Source to the Destination.
  • Once Communication has ended, the connection must be “torn down” to free up resources for other services.
  • Minimal variation in propagation delays (from the Source to the Destination).
  • This means the transit time through the connection is usually close to constant.
  • Typically involves the use of a dedicated link or communication media
  • Uses Static Bandwidth allocation as opposed to Dynamic Bandwidth allocation.

In Figure 2, I show one of the features of a Connection-Oriented Communication System. If we send Data Blocks A through E out (in that order), it will arrive at the other end in the same order (or sequence).

Connection-Oriented Communication Feature -the Sequence of Data sent by the Transmitter is Retained by the Receiver.

Figure 2, The Order/Sequence of Data, as it arrives at the Receiver, is the same as the order in which it was sent (at the Transmitter).

Hence, there is no need to re-order the sequence of data (to keep data in its proper order at the Destination).

Figure 3 shows another feature of a Connection-Oriented Communication System: the Nearly Constant Propagation Delay Times through the Network.

If it takes time, t, for a block of data to transit the network, it will typically take time, t, for all other blocks to traverse the network. There is minimal deviation in t for Connection-Oriented Networks.

Connection-Oriented Communication offers Nearly Constant Propagation delay through the Network.

Figure 3, All Data Blocks passing through a Connection-Oriented Communication System will have a Nearly Constant Propagation Delay time through the network.

This feature means that Connection-Oriented Communication is typically very good for real-time services (such as Voice or Video).

Some Disadvantages of Connection-Oriented Communication

One downside of Connection-Oriented Communication is that it does require dedicated bandwidth.

Other services are typically “locked out” and cannot use this bandwidth.

Examples of Connection-Oriented Communication

  • Voice Phone Call
    • You must dial your friend’s (or other party’s) number, and they MUST pick up their phone (completing the connection setup) before your conversation can begin.
An Example of Connection-Oriented Communication - the Phone Call

Figure 4, Example of Connection-Oriented Communication – the Phone Call

Examples of Technologies/Protocols Using Connection-Oriented Communication

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Author: Darrell Smith

Darrell Smith has more than 30 years of experience as an Electrical Engineer. He has about 20 years of experience as an Applications Engineer and the remainder of his time was spent in Hardware Design and Product Marketing. He will now be sharing his wealth of knowledge on this blog.

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