Transmission Control Protocol (TCP)

TCP is a commonly used Protocol# in #Internet Protocol Suite (TCP/IP). It is a #Transport Layer protocol according to the classification of #Open Systems Interconnection (OSI) Model.

TCP is designed to be connection-oriented and reliable, in contrast to User Datagram Protocol (UDP). This means that connection must be established first (using three-way handshake) via a full-duplex channel and maintained by the protocol during a transmission. The requester will first send out a control bit SYN (stand for synchronisation) and its Initial Sequence Number (ISN) to the server. The server sends back a packet to the requester that contains the control bit ACK (stand for acknowledgement) and its ISN. From now on, the requester will assume the connection is well established, and it will send packets to the server with incremented SYN and ACK (same to the server). This way, TCP can guarantee the eventual orderly delivery of the packets.

It breaks messages into segments (its Protocol Data Units (PDU)#) and reassemble at the destination. If there is a failure on sending such messages, TCP will resend it. It also provides virtual circuits between application. At the end, the connection will be torn down if there is no need for it.

To improve the performance, the overhead of the connection tunnel must be addressed. This could be done by windowing, a method where the device sends ACK only when it has received enough packets. The consensus about the size of window can be reached after the server send back an ACK packet with the information of the window size that it can achieve (usually after a packet has failed to be sent to the server). Furthermore, it has an additional benefit of handling the edge case where the sender could send too much, too fast which could overflow the receiver’s buffer.

Examples of TCP:

Diameter#

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Well-Known Ports

There are several well-known ports for #Transmission Control Protocol (TCP) and #User Datagram Protocol (UDP) authorised by Internet Assigned Numbers Authority (IANA) for #Application Layer protocols ranged from 0 to 1023. They are shown in the following table:
User Datagram Protocol (UDP)

UDP is a widely used #Transport Layer Protocol# (defined by #Open Systems Interconnection (OSI) Model for the #Internet Protocol Suite (TCP/IP). Unlike Transmission Control Protocol (TCP), it is an unreliable and connectionless protocol which is great for real time communication such as voice chat or video streaming. UDP doesn’t guarantee that the packets or datagram (its Protocol Data Units (PDU))# will reach their destination or arrive in order as there is no mean to acknowledge such state. It has a rather small segment headers, with only 8 bytes, and provides fine application control over data transmission, which allow application-specific error recovery at Application Layer# for reliability.
Transport Layer

Transmission Control Protocol (TCP)#
TTP3121 Chapter 1: Introduction

Transmission Control Protocol (TCP)
Socket Programming

In Transmission Control Protocol (TCP)# connection, client requires fewer steps than server. First, like server, it needs to establish a socket. Thereafter, client will connect itself to the socket. And then, it will wait for the response from the server and receive any data transmitted from there.

To establish a Transmission Control Protocol (TCP)# connection, a server often has such procedure: First, it needs to establish a socket. Next, it needs to bind the corresponding socket to a dedicated IP and port. Then, it will listen to the socket and wait for accepting incoming connection. If there is a client established a connection, it can then send any data, if they are available, to the client.
Security Association (SA)

Traffic Type (TCP# or UDP#)
Secure Shell (SSH)

SSH is a protocol that aim to establish a secure #202206151232 connection between two computers. It uses the #202203221212 in order to secure the network communication between two hosts. Additionally, one could utilise the 202203221227# feature in order to Encapsulation# one Protocol (usually insecure) under SSH thus enhance the security of the protocol.
SSH Tunnelling

#Secure Shell (SSH) could be used to tunnel insecure #Transmission Control Protocol (TCP) connections such as File Transfer Protocol (FTP) or IMAP if the configuration AllowTcpForwarding is enabled. This provides a secure layer onto the TCP connection without resort to displacing such protocol within a network.
SNMPv2 1993

SNMP supports both central and distributed management (multiple Management Station or Manager with a pool of Management Agent) as each device in the network maintains local Management Information Base (MIB). The communication is usually done in User Datagram Protocol (UDP)# but SNMPv2 allows the use of Transmission Control Protocol (TCP)# too.
Network Congestion

Network Congestion is networking condition which could happen when there are too many sources sending too much data too fast for network to handle. This phenomenon could be observed when there are packet losses (due to buffer overflow at Routers and increasing end-to-end delays (due to queuing in router buffers). The result is the unfairness and poor utilisation of network resources due to resources used by dropped packets before they were lost, retransmissions, and poor resource allocation at high load.
Internet Protocol Suite (TCP/IP)

Transmission Control Protocol (TCP)#
Internet Protocol (IP)

Transmission Control Protocol (TCP)#
Internet Printing Protocol (IPP)

IPP is a #202206151232 mainly used by #202205301742 to communicate to each other. It supports browsing feature which enable computer on a local network to exchange printer list automatically. This can be enable by setting the option Browsing in CUPS to On. It usually listens to the well-known port 631.
Differentiated Service

DNS (TCP query)
Diameter

Diameter is a new #Triple A (AAA) protocol standardised by RFC3588 and RFC4005. It is derived from and aim to replace Remote Access Dial-In User Service (RADIUS) (also provides the transition support) with enhancements such as error handling and message delivery reliability. Instead of relying on a central AAA server, it employs a peer-to-peer architecture, which means that every host or node that implements Diameter could act as either a server or client, with additional support of peer discovery via static configuration or dynamic lookup. The protocols in used by Diameter are connection-oriented protocols such as #Transmission Control Protocol (TCP) and Stream Control Transmission Protocol (SCTP) with a maximum attribute data size of 16,777,215 octets (8 bit). It supports both Link Encryption# and End-to-end Encryption (e2e)#.

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