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Internet Protocol Reference


One of the most common poorly understood terms is 'protocol'. There are a large number of these protocols in common use on the internet, so we list some of the most common ones here on the home page. For more details, see the main internet dictionary.

FTP file transfer protocol
HTTP hypertext transfer protocol
NNTP network news transfer protocol
POP post office protocol
SMTP simple mail transfer protocol

A protocol is basically a set of rules and instructions to enable computers to communicated with each other, even if the computers are running on completely different operating systems. You can perhaps think of it as a sort of secret handshake, where two people meet who don't know each other, but they are both members of the same club, and know the secret handshake.

Another commonly misunderstood term is 'search engine'. There are actually two main types of search engine. One uses automated searchers called robots, bots, crawlers, or spiders. Spiders crawl the web every 2 or 3 weeks searching for new web pages. The ones they find are added to their search engines index, which the search engine scours according to the keywords that the user has input. The other type is the Directory. Here, new web pages are added to the index or database by human beings. Directories tend to offer greater quality, but less quantity than spiders.


There are lots of protocols on the internet, and they seem quite bewildering to many. But once you understand what a protocol is, it all becomes intelligible.

So what's a protocol? Well, there are all kinds of different computer systems out there on the Web. Some computers run on UNIX, some on Windows, others on Linux. Without protocols, these computers would not be able to talk to each other at all. A protocol is a set of rules and procedures that all computers agree to follow. So when two Computers connect with a particular Protocol, they can talk to each other no matter what operating system they are running on.

You can think of a protocol as a kind of secret hand shake. And there are lots of different secret hand shakes, depending on what you want to do.


Ftp stands for File-Transfer-Protocol. This is the one that you uses if you want to upload or download files from another Computer. In order to up- or download, you need a piece of ftp software. This is called an ftp program, or Client. When you want to connect to the remote computer (server) you have to indicate that you want to connect to the FTP server. Ths will have an address something like ftp.somename.com. When you connect to this srver, your computer and the remote-server agree to use the File- Transfer-Protocol. Once both computers are connected with this protocol between them, files can be easily exchanged. Try Cute FTP, or WS_FTP. Both of these are good FTP clients.


This stands for Hyper-Text-Transfer-Protocol. Hypertext is the programming language that is used for creating web pages. http is used for transferring web pages to your browser. When you type in a web address, it is preceded by http://www.somename.com The http tells the remote-computer that you want to connect to its web-server.


SMTP stands for Simple- Mail-Transfer-Protocol. To connect to a mail-Server, you need a mail program, sometimes called a mail-client. Microsoft's Outlook Express is a mail client. The mail-server will have an address something like mail.somename.com. When you request your e-mail using your mail-client, it connects to the mail server using the mail-protocol This enables mail to be delivered.


This stands for Network-News-Transfer-Protocol. The news server of your Internet Service Provider will have an address something like news.somename.com. To connect to the news-server, you need a news program or Client. You connect to the remote cmpter, and both computers agree to use the NNTP. Newsgroup postings can then be delivered to you.


This is a special protocol. It stands for Terminal Emulation Local Network. Emulation just means pretend. When you connect to a remote computer using TELNET, it instructs your computer how to pretend to be part of the local network that the remote Computer belongs to. Once your pc has initiated the emulation, you can log onto the remote Computer as if you were a normal terminal on its local network. You can view anything on the remote computer that you have privileges to do.


This stands for internet-protocol. This is the one that you use when you dial into the internet through your service provider. The Internet-Protocol simply tells your service providers host computer that you want to log on to the main-server and surf the net.


This means Point-to-Point-Protocol. This is just another protocol for dialing in to your service provider. PPP always gives full unrestricted access to the internet.


Transmission-Control-Protocol. You will often see this combined with IP in the format IP/TCP. Again, just another way of dialing up to your service provider. This one may connect you to a server on a closed network on the internet. AOL and Compuserve have special services only available to members logging into the net. You can still leave the AOL network, surf the web, then return to AOLs service page, so long as you are still signed on as an AOL member, which you almost certainly will be.



Protocol Acronyms


AAL             ATM Adaptation Layer

AAL0           ATM Adaptation Layer Type 0 refers to raw ATM cells.

AAL1           ATM Adaptation Layer Type 1 supports constant bit rate, time dependent traffic such as voice and video.

AAL2           ATM Adaptation Layer Type 2 reserved for variable bit rate video transfer.

AAL3/4        ATM Adaptation Layer Type 3/4 supports variable bit rate, delay tolerant data traffic requiring some sequencing and/or error detection support.

AAL5           ATM Adaptation Layer Type 5 supports variable bit rate, delay tolerant connection oriented data traffic requiring minimal sequencing or error detection support.

AARP          AppleTalk Address Resolution Protocol

ADSP          AppleTalk Data Stream Protocol

AEP             AppleTalk Echo Protocol

AFP             AppleTalk Filing Protocol

ARP/RARP    Address Resolution Protocol / Reverse Address Resolution Protocol

ASP             AppleTalk Session Protocol

ATCP          AppleTalk Control Protocol

ATM             Asynchronous Transfer Mode

ATP             AppleTalk Transaction Protocol



BACP          Bandwidth Allocation Control Protocol (PPP suite)

BAP             Bandwidth Allocation Protocol (PPP suite)

BCAST        Broadcast Protocol (Novell protocols)

BCC            Broadcast Call Control

BCP             Bridging Control Protocol (PPP suite)

BGP4          Border Gateway Protocol (TCP/IP)

BICI              BISDN Inter Carrier Interface (ATM PNNI Signaling)

BMP (Burst)   Burst Mode Protocol (Novell protocols)

BPDU          Bridge Protocol Data Unit

BRE             Bridge Relay Encapsulation, proprietary Ascom Timeplex protocol that extends bridging across WAN links by means of encapsulation (Frame Relay).

BVCP          PPP Banyan VINES Control Protocol (PPP suite)



CCITT          International Telegraph and Telephone Consultative Committee (after the French)

CCP            Compression Control Protocol (PPP suite)

CHAP          Challenge Handshake Authentication Protocol (PPP suite)

CIF               Cells in Frames (ATM over LAN)

COPS          Common Open Policy Service

CTERM       Command Terminal (DECnet)



DAP             Data Access Protocol (DECnet)

DCAP          Data Link Switching Client Access Protocol 

DCP            Data Compression Protocol over Frame Relay

DCPCP       DCP Control Protocol

DDP            Datagram Delivery Protocol (AppleTalk)

DECnet       Digital Equipment Corporation protocols developed to communicate between DEC minicomputers.

DHCP          Dynamic Host Configuration Protocol (TCP/IP)

DIAG            Diagnostic Responder protocol (Novell)

DLSw          Data Link Switching (IBM SNA)

DNCP          PPP DECnet Phase IV Control Protocol (PPP suite)

DNS             Domain Name Server protocol (TCP/IP)

DSMCC      Digital Storage Media Command and Control (Audio Visual over ATM)

DVB             Digital Video Broadcasting



ECP             Encryption Control Protocol (PPP suite)

ESIS            End system to Intermediate System protocol (ISO protocols)

Ethernet       LAN protocol synonymous with IEEE 802.3 standard



FANAP       Flow Attribute Notification Protocol

FDDI            Fiber Distributed Data Interface, standardized by ANSI

FTP              File Transfer Protocol (TCP/IP)

FUNI            Framebased UNI (User Network Interface)



GCC            Group Call Control

GMM            GPRS Mobility Management

GSM            GPRS Session Management

GSMP         General Switch Management Protocol (IP Switching)

GTP            GPRS Tunnelling Protocol



HDLC          High Level Data Link Control protocol developed by ISO, based on pioneering work by IBM on SDLC.

HPRAPPN High Performance Routing Advanced Peer to Peer Network, IBM network architecture for dynamic routing across arbitrary network topologies.

HTTP           Hypertext Transfer Protocol (TCP/IP)



ICMP           Internet Control Message Protocol (TCP/IP)

ICMPv6       revision of ICMP (TCP/IP)

ICP               Internet Control Protocol (Banyan)

IDP               Internet Datagram Protocol (XNS)

IFMP            Ipsilon Flow Management Protocol (IP Switching)

IGMP           Internet Group Management Protocol (TCP/IP)

IGRP            Interior Gateway Routing Protocol (TCP/IP)

IISP              Interim Interswitch Signalling Protocol (ATM Signalling)

ILMI              Interim Local Management Interface, bidirection exchange of management information between UMEs.

IP                  Internet Protocol, routing layer datagram service of the TCP/IP suite.

IPC               InterProcess Communications protocol, datagram and reliable message delivery service for Banyan.

IPCP            IP Control Protocol, responsible for configuring the IP parameters on both ends of the PPP link.

IPHC            IP Header Compression 

IPv6              revised version of IP (TCP/IP)

IPv6CP        IPv6 PPP Control Protocol, responsible for configuring, enabling and disabling the IPv6 protocol modules on both ends of a PPP link.

IPX               Internetwork Packet Exchange, Novell's implementation of the Xerox Internet Datagram Protocol (IDP).

IPXCP         IPX PPP Control Protocol, choose and configure the IPX networklayer protocol over PPP.

ISDN            Integrated Services Digital Network, all digital communications line that allows for transmission of voice, data, video and graphics, at very high speeds, over standard communication lines.

ISIS (ISO 10589)       Intermediate System to Intermediate System, exchage of configuration and routing information to facilitate the operation of the routing and relaying functions of the network layer (ISO).

ISO               International Standards Organization protocols defined by IEEE; complete sevenlayer protocol conforming to the OSI networking model.

ISOIP           ISO Internetworking Protocol, includes builtin error signalling to aid in routing management.

ISOSP         ISO Session Protocol, specifies procedures for a single protocol for the transfer of data and control information from one session entity to a peer session entity.

ISOTP (ISO 8073)     ISO Transport Protocol

ISUP            ISDN User Part of SS7, defines protocol and procedures used to seup, manage and release trunk circuits that carry voice and data calls over the public switched telephone network.

ITU Q.2931 Signalling          International Telecommunications Union signalling standard for ATM to support Switched Virtual Connections. This is the signalling standard for ISDN.



L2F              Layer 2 Forwarding protocol, permits the tunneling of the link layer of higher layer protocols (PPP suite).

L2TP            Layer 2 Tunneling Protocol, used for integrating multiprotocol dialup services into existing ISP POP.

LAPB           Link Access Protocol, Balanced, derived from HDLC and used to carry X.25 packets.

LAPD          Link Access Protocol, Channel D, layer 2 protocol defined in CCITT.

LAPF           Link Access Procedure F (Frame Relay), modified LAPD standard for Frame Relay.

LAT              Local Area Transport protocol, designed to handle multiplexed terminal traffic to/from timesharing hosts (DECnet).

LAVC          Local Area VAX Cluster protocol, communications between DEC VAX computers in a cluster (DECnet).

LDAP          Lightweight Directory Access Protocol

LDP             Label Distribution Protocol

LCP             Link Control Protocol, establishes, configures and tests the data link connection (PPP suite).

LLC              Logical Link Control protocol (IEEE 802.2), provides a link mechanism for upper layer protocols.

LQR             Link Quality Report, specifies the mechanism for link quality monitoring with PPP.




M2UA      used for backhauling of SS7 MTP2-User signalling messages over IP using Stream Control Transmission Protocol (SCTP)

M3UA       supports transport of SS7 MTP3-User sugnalling over IP using Stream Control Transmission Protocol (SCTP)

MAPOS       Multiple Access Protocol over SONET / SDH

MARS          Multicast Address Resolution Server (TCP/IP)

Megaco       Media Gateway Control

MLP             Multilink Procedure, added upper sublayer of the LAPB, operating between the packet layer and a multiplicity of single data link protocol functions (SLPs) in the data link layer (X.25).

MOP            Maintenance Operation Protocol, utility services such as uploading and downloading system software, remote testing and problem diagnosis (DECnet).

MOUNT       protocol used to initiate client access to a server supporting NFS.

MPEG         Motion Picture Experts Group, ISO standards group dealing with video and audio compression.

MPLS          Multi Protocol Label Switching, set of procedures for augmenting network layer packets with "label stacks", thereby turning them into labeled packets.

MPOA         Multi Protocol Over ATM, deals with efficient transfer of innersubnet unicast data in a LAN emulation environment.

MPPC         Microsoft PointtoPoint Compression Protocol

MTP2           Message Transfer Part, Level 2, signalling link which together with MTP3 provides reliable transfer of signalling messages between two directly connected signalling points (SS7).

MTP3           Message Transfer Part, Level 3, connects Q.SAAL to the users (SS7 suite).



NBFCP       PPP NetBIOS Frames Control Protocol, network control protocol responsible for establishing and configuring the NBF protocol over PPP.

NBP             AppleTalk Name Binding Protocol, manages the use of names on AppleTalk networks.

NBMA          NonBroadcast, MultiAccess.

NCP             Novell NetWare Core Protocol, manages access to the primary NetWare server resources.

NDS             NetWare Directory Services (Novell), globally distributed network database that replaces the bindery used in previous versions of NetWare.

NetRPC       NetRemote Procedure Call, used to access VINES applications such as StreetTalk and VINES Mail (Banyan).

NFS             Sun Network File System, file sharing application for the Sun protocol suite.

NHDR          Network Layer Header, begins the frame used by RTP nodes.

NHRP          NBMA Next Hop Resolution Protocol.

NSP             Network Services Protocol, provides reliable virtual connection services with flow control to the network layer Routing Protocol (DECnet).

NTP             Network Time Protocol, time synchronization system for computer clocks through the Internet network (TCP/IP).



OSINLCP    OSI Network Layer Control Protocol, responsible for configuring, enabling and disabling the OSI protocol modules on both ends of the PPP link.

OSPF          Open Shortest Path First, linkstate routing protocol used for routing IP (TCP/IP).



PAP             Printer Access Protocol, manages the virtual connection to printers and other servers (AppleTalk).

PAP             Password Authentication Protocol, provides a simple method for the peer to establish its identity using a 2way handshake (PPP suite).

PEP             Packet Exchange Protocol, provides a semireliable packet delivery service that orients towards singlepacket exchanges (XNS).

PIM              Protocol Independent MulticastSparse Mode (PIMSM)

PMAP          Port Mapper protocol, manages the allocation of transport layer ports to network server applications (Sun).

PNNI            Private NetworktoNetwork Interface, hierarchial, dynamic linkstate routing protocol (ATM).

POP3          Post Office Protocol version 3, permits workstations to dynamically access a maildrop on a server host (TCP/IP).

PP                ISO Presentation Protocol, performs context negotiation and management between open systems.

PPP             PointtoPoint Protocol, designed for simple links which transport packets between two peers.

PPP Multilink             Multilink PointtoPoint Protocol, permits a system to indicate to its peer that it is capable of combining multiple physical links into a "bundle".

PPPBPDU PPP Bridge Protocol Data Unit, used to connect remote bridges.

PPTP           PointtoPoint Tunneling Protocol, allows PPP to be channeled through an IP network (PPP).



QLLC           Qualified Logical Link Control protocol, transfers IBM SNA data over an X.25 network.



RANAP - Radio Access Network Application Part is the Radio Netwok Layer sugnalling protocol for the Iu interface.

RIP               Routing Information Protocol, maintains a database of network hosts and exchange information about the topology of the network (XNS).

RIP2             Routing Information Protocol, used by Berkeley 4BSD UNIX systems to exchange routing information. RIP2 derives from the Xerox protocol of the same name (TCP/IP).

RIPX            Routing Information Protocol, used to collect, maintain and exchange correct routing information among gateways within the Internet (Novell).

RFC             Request for Comments, a series of notes about the Internet, started in 1969 (when the Internet was the ARPANET). The notes discuss many aspects of computing and computer communication focusing in networking protocols, procedures, programs, and concepts, but also including meeting notes, opinion, and sometimes humor. The specification documents of the Internet protocol suite, as defined by the Internet Engineering Task Force (IETF) and its steering group (the IESG), are published as RFCs. Many of the TCP/IP protocols and PPP protocols are defined by rfc's.

RLOGIN       Remote Login, allows UNIX users of one machine to connect to other UNIX systems across the Internet and interact as if their terminals are directly connected to the machines (TCP/IP).

RLP             Radio Link Protocol

RM Cells     Rate Management cells (ATM cells).

RND             name of a company which uses a proprietary protocol header (RND) to transfer LAN protocols via WAN.

RP                Routing Protocol, distributes routing information among DECnet hosts.

RPC             Remote Procedure Call protocol, activates a function on a remote station and retrieves the result (Sun).

RSVP          Resource ReSerVation setup Protocol, designed for an integrated services Internet (TCP/IP).

RTMP          Routing Table Maintenance Protocol, manages routing information for AppleTalk networks.

RTP             Routing Update Protocol, used to distribute network topology (Banyan).

RUDP          Reliable UDP

RVP             Remote Voice Protocol



SAP             Novell's Service Advertising Protocol, provides information about what servers are available on the network.

SCCP          Signalling Connection Control Part, offers enhancements to MTP level 3 to provide connectionless and connectionoriented network services, as well as to address translation capabilities (SS7).

SCP             Session Control Protocol, manages logical links for DECnet connections.

SCSP          is a routine protocol in the TCP/IP family.

SCTP          Stream Control Transmission Protocol

SDP             Session Description Protocol

SDCP          PPP Serial Data Control Protocol, responsible for configuring, enabling and disabling the SDTP modules on both ends of the pointtopoint link.

SDLC          Synchronous Data Link Control protocol, developed by IBM to be used as the layer 2 of the SNA hierarchical network.

SER             Serialization packet, ensures that a single version of NetWare is not being loaded on multiple servers.

SIP               SMDS Interface Protocol, threelevel protocol that controls access to the network.

SIP (VoIP)   Session Initiation Protocol

SLP             Servise Location Protocol

SMB            Server Message Block, Microsoft presentation layer protocol providing file and print sharing functions for LAN Manager, Banyan VINES and other networking operating systems.

SMDS         Switched Multimegabit Data Service, broadband networking technology developed by Bellcore.

SMPP    Short Message Peer to Peer

SMTP          Simple Mail Transfer Protocol, mail service modeled on the FTP file transfer service (TCP/IP).

SMS          Short Message Service (UMTS).

SMS          Short Message Service.

SNA             Systems Network Architecture, introduced by IBM to provide a framework for joining together many mutually incompatible IBM products for distributed processing.

SNACP       SNA PPP Control Protocol, responsible for configuring, enabling and disabling SNA on both ends of the pointpoint link (PPP).

SNMP          Simple Network Management Protocol, developed by the Internet community to allow diverse network objects to participate in a global network management architecture.


SPANS       Simple Protocol for ATM Network Signalling, developed by FORE Systems for use in ATM networks.

SPP             Sequenced Packet Protocol, provides a reliable virtual connection service for private connections (Banyan).

SPP             Sequenced Packet Protocol, provides reliable transport delivery with flow control (XNS).

SPX             Sequential Packet Exchange, Novell's version of Xerox SPP. It is a transport layer protocol providing a packet delivery service for third party applications.

SRB             Source Routing Bridging, proprietary header of Bay Networks which passes Token Ring information over WAN lines.

SRP            Spatial Reuse Protocol.

SS7             Signalling System 7, a common channel signalling system.

STP             Spanning Tree Protocol, prevents the formation of logical looping in the network (DECnet).



TALI             Transport Adapter Layer Interface

TCAP          Transaction Capabilities Application Part, enables the deployment of advanced intelligent network services by supporting noncircuit related information exchange between signalling points using the SCCP connectionless service (SS7).

TCP             Transmission Control Protocol, provides a reliable stream delivery and virtual connection service to applications through the use of sequenced acknowledgement with retransmission of packets when necessary (TCP/IP).

TDP             Tag Distribution Protocol, a two party protocol that runs over a connection oriented transport layer with guaranteed sequential delivery.

TELNET      Terminal emulation protocol of TCP/IP.

TFTP           Trivial File Transfer Protocol, supports file writing and reading (TCP/IP).

THDR          Transport Layer Header, used by RTP endpoints to provide correct processing of the packet (SNA).

Timeplex (BRE2) Bridge Relay Encapsulation, proprietary Ascom Timeplex protocol that extends bridging across WAN links by means of encapsulation (Frame Relay).

Token Ring LAN protocol where all stations are connected in a ring and each station can directly hear transmissions only from its immediate neighbor.



UDP             User Datagram Protocol, provides a simple but unreliable message service for transactionoriented services (TCP/IP).


UNI               User Network Interface, an interface point between ATM end users and a private ATM switch, or between a private ATM switch and the public carrier ATM network.


Van Jacobson compressed TCP protocol which improves the TCP/IP performance over low speed serial links.

VARP          VINES Address Resolution Protocol, used for finding the node Data Link Control address from the node IP address (Banyan).

VCI               Virtual Channel Identifier.

VGCS          Voice Group Call Service

ViVID MPOA proprietary protocol of Newbridge which provides bridged LAN Emulation and routed LAN Emulation functionality.

VPI               Virtual Path Identifier

VRRP          Virtual Router Redundancy Protocol



WAE            Wireless Application Environment

WAP            Wireless Application Protocol

WCCP         Web Cache Coordination Protocol

WDOG        Watchdog protocol, provides constant validation of active workstation connections and notifies the NetWare operating system when a connection may be terminated as a result of lengthy periods without communication (Novell).

Wellfleet BOFL Wellfleet Breath of Life, used as a line sensing protocol.

Wellfleet SRB Source Routing Bridging, proprietary header of Bay Networks which passes Token Ring information over WAN lines.


WSP            Wireless Session Protocol

WTLS          Wireless Transport Layer Security

WTP            Wireless Transaction Protocol




X.25             CCITT's recommendation for the interface between a DTE and DCE over a PSTN.

X.75             Signalling system which is used to connect packet switched networks (such as X.25) on international circuits.

XNS             Xerox Network System protocols, provide routing capability and support for both sequenced and connectionless packet delivery.

XOT             Cisco Systems' X.25 over TCP.



YP (NIS)      Sun Yellow Pages protocol, known now as Network Information Service, is a directory service used for name lookup and general table enumeration.



ZIP               AppleTalk Zone Information Protocol, manages the relationship between network numbers and zone names.





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