Connectionless versus Connection-Oriented
Communications
Characteristics of Connectionless Communication Protocols




Each packet is an individual message
Speed is more important than reliability—transmission delay is unacceptable
Fewer services leads to low overhead but may cause network congestion
Can be used to broadcast or multicast (sending messages to more than one receiver)
Characteristics of Connection-Oriented Communication Protocols




Sender and receiver establish a connection
Reliability is more important than speed—data loss is unacceptable
More services leads to high overhead but may reduce overall network traffic
Best for exchanging multiple messages between two hosts
Connectionless and Connection-Oriented Communication Comparison Using Common Protocols
User Datagram Protocol (UDP)
Transmission Control Protocol (TCP)
Type

Connectionless

Connection-oriented
Reliability

No acknowledgement from receiver


Lost packets are not retransmitted
Each transmission is acknowledged
by the receiver

“Best effort” delivery of data

Lost packets are retransmitted

Data delivered out of order is reordered

Corrupt data is discarded

Corrupt data is retransmitted

Duplicate data is retained

Duplicate data is discarded
Flow
Control

None—not needed or performed by
application

Receiver indicates speed at which it
will accept data
Applications
Using
Protocol

Support services (DHCP, DNS,
SSDP, SNMP)

Email (POP, IMAP, SMTP)

Internet Relay Chat (IRC)

Streaming media (RTP, RTPC)

File transfer (FTP)

File transfer (TFTP)

Web services (HTTP, HTTPS)
Integrity
© 2022 by Jones & Bartlett Learning, LLC, an Ascend Learning Company. All rights reserved.
www.jblearning.com
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Connectionless versus Connection-Oriented
Communications
Connectionless Communication Diagram (UDP)
Data
Data
Data
Server
Client
Connection-Oriented Communication Diagram (TCP)
Establishing the Connection
Client Requests Connection
Server Acknowledges
Client Acknowledges
Client
Server
Communicating
Data Write/Read
Data Write/Read
Closing the Connection
Client Sends Close Request
Server Acknowledges Request
Server Sends Close Request
Client Acknowledges Request
© 2022 by Jones & Bartlett Learning, LLC, an Ascend Learning Company. All rights reserved.
www.jblearning.com
Page 2