In networking, a communications protocol or network protocol is the specification of a set of rules for a particular type of communication.

Different protocols often describe different aspects of a single communication; taken together, these form a protocol stack. The terms "protocol" and "protocol stack" also refer to the software that implements a protocol.

Most recent protocols are assigned by the IETF for internet communications, and the IEEE, or the ISO organizations for other types. The ITU-T handles telecommunications protocols and formats.

Index page for network protocols and protocol layers, categorised by the nearest matching layers of the OSI seven layer model.

Systems engineering principles have been applied to design network protocols.

Table of contents

1 Protocol Families 2 Individual Protocols 2.1 Layer 1 protocols 2.2 Layer 2 protocols 2.3 Layer 2+3 protocols 2.4 Layer 3 protocols 2.5 Layer 3+4 protocols 2.6 Layer 4 protocols 2.7 Layer 5+ protocols 2.8 Layer 7 protocols 3 Related Items 3.9 Protocol Description Languages

Protocol Families

Various protocol stacks or families

• AppleTalk
• DECnet
• IPX/SPX
• Open Systems Interconnect (OSI)
• SNA
• Internet protocol suite

Individual Protocols

Layer 1 protocols

• ISDN Integrated Services Digital Network
• PDH Plesiochronous Digital Hierarchy
  • T-carrier (T1, T3 etc)
• RS-232, a serial line interface originally developed to connect modems and computer terminals
• SDH Synchronous Digital Hierarchy
• SONET Synchronous Optical NETworking

Layer 2 protocols

• ARP Address Resolution Protocol
• Ethernet
• FDDI Fiber Distributed Data Interface
• HDLC High Level Data Link Control
• PPP Point-to-point protocol
• Token ring

Layer 2+3 protocols

• X.25
• Frame relay, a simplified version of X.25
• ATM Asynchronous Transfer Mode
• MPLS Multi-protocol label switching

Layer 3 protocols

• ICMP Internet Control Message Protocol
• IP the Internet Protocol itself
  • IPv4 Internet Protocol version 4, the current standard
  • IPv6 Internet Protocol version 6, in the process of deployment
• IPX
• Routing protocols:
  • Routing between autonomous systemss
    • EGP Exterior gateway protocol (obsolete)
    • BGP Border gateway protocol
  • Routing within a single Autonomous System
    • EIGRP Enhanced interior gateway routing protocol
    • IGRP Interior gateway routing protocol
    • RIP Routing information protocol
    • OSPF Open shortest path first

Layer 3+4 protocols

• Xerox network services (XNS)

Layer 4 protocols

• SPX Sequenced Packet Exchange
• TCP Transmission Control Protocol
• UDP User Datagram Protocol

Layer 5+ protocols

• IMAP Internet Message Access Protocol
• NFS Network File System

Layer 7 protocols

• FTP File Transfer Protocol
• HTTP HyperText Transport Protocol, used in the World Wide Web
• POP3 Post Office Protocol Version 3
• SNMP Simple Network Management Protocol
• SMTP Simple Mail Transfer Protocol
• Telnet, a remote terminal access protocol
• Gnutella, a peer-to-peer file-swapping protocol
• DNS Domain Name Service
• SSH Secure SHell
• IMAP Internet Message Access Protocol
• NTP Network Time Protocol
• Gopher, a precursor of web search engines
• Finger, which gives user profile information
• NNTP News Network Transfer Protocol
• LDAP Lightweight Directory Access Protocol
• DHCP Dynamic Host Configuration Protocol
• IRC Internet Relay Chat
• WebDAV Web Distributed Authoring and Versioning
• DICT Dictionary protocol

and secure versions of the above (as HTTPS, etc.)

Related Items

Protocol Description Languages

• ASN.1 Abstract Syntax Notation One