A reliable byte stream is a common service paradigm in computer networking; it refers to a byte stream

Byte stream

In computer science, a byte stream is a bit stream, in which data bits are grouped into units, called bytes.In computer networking the term octet stream is sometimes used to refer to the same thing; it emphasizes the use of bytes having the length of 8 bits, known as octets.Formally, a byte stream...

 in which the byte

Byte

The byte is a unit of digital information in computing and telecommunications that most commonly consists of eight bits. Historically, a byte was the number of bits used to encode a single character of text in a computer and for this reason it is the basic addressable element in many computer...

s which emerge from the communication

Communication

Communication is the activity of conveying meaningful information. Communication requires a sender, a message, and an intended recipient, although the receiver need not be present or aware of the sender's intent to communicate at the time of communication; thus communication can occur across vast...

 channel at the recipient are exactly the same, and in exactly the same order, as they were when the sender inserted them into the channel.

The classic example of a reliable byte stream communication protocol is the Transmission Control Protocol

Transmission Control Protocol

The Transmission Control Protocol is one of the core protocols of the Internet Protocol Suite. TCP is one of the two original components of the suite, complementing the Internet Protocol , and therefore the entire suite is commonly referred to as TCP/IP...

, one of the major building blocks of the Internet

Internet

The Internet is a global system of interconnected computer networks that use the standard Internet protocol suite to serve billions of users worldwide...

.

A reliable byte stream is not the only reliable service paradigm which computer network communication protocols provide, however; other protocols (e.g. SCTP) provide a reliable message stream, i.e. the data is divided up into distinct units, which are provided to the consumer of the data as discrete objects.

Mechanism

Communication protocols which implement reliable byte streams, generally over some unreliable lower level, use a number of mechanisms to provide that reliability. ARQ protocols have an important role for achieving reliability.

All data items are identified with a sequence number, which is used both to make sure that the data are delivered to the entity at the other end in the correct order, and to check for lost data items. The receiver sends back acknowledgements for data items which have been successfully received; a timer at the sender will cause a timeout if an acknowledgement is not received within a reasonable round trip time, and the (presumably lost) data will then be re-transmitted

Retransmission (data networks)

Retransmission, essentially identical with Automatic repeat request , is the resending of packets which have been either damaged or lost. It is a term that refers to one of the basic mechanisms used by protocols operating over a packet switched computer network to provide reliable communication...

. To check that no data items are damaged, a checksum

Checksum

A checksum or hash sum is a fixed-size datum computed from an arbitrary block of digital data for the purpose of detecting accidental errors that may have been introduced during its transmission or storage. The integrity of the data can be checked at any later time by recomputing the checksum and...

is used; one is computed at the sender for each block of data before it is sent, and checked at the receiver. Erroneous or missing data are reported to the sender, in order that it may retransmit the same. Any duplicated data items are discarded.