Common network protocols
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Common network protocols

A protocol is a set of rules which is used by computers to communicate with each other across a network. A protocol is a convention or standard that controls or enables the connection, communication, and data transfer between computing endpoints. In its simplest form, a protocol can be defined as the rules governing the syntax, semantics, and synchronization of communication. Protocols may be implemented by hardware, software, or a combination of the two. At the lowest level, a protocol defines the behavior of a hardware connection. The following are some common protocols:

1. IPX / SPX (NWLink): Internetwork Packet Exchange/Sequenced Packet Exchange. The default network protocol for Novell Netware prior to NetWare 5. (Current default is TCP/IP). NWLink is the Microsoft version of IPX/SPX.

2. NETBEUI / NetBIOS: These two terms are grouped together by many technical resources, which can be misleading. NetBEUI is the NetBIOS Extended User Interface. A non-routable protocol for early Windows OS. NetBIOS is a provides three services to applications: Name service registration and resolution, Session service (connection-oriented), and Datagram distribution (connectionless). By definition, NetBEUI uses NetBIOS. However, NetBIOS does not depend upon NetBEUI. For example, NetBIOS services occur over TCP/IP in Windows environments.

3. TCP / IP: Transmission Control Protocol/Internet Protocol. Part of a set of protocols known as the Internet Protocol Suite. The most commonly used, routable, network protocol. TCP transmits data and IP refers to addressing. Necessary for Internet communication. All protocols below (except DNS) occur over TCP/IP

4. UDP: User Datagram Protocol. It is one of the core members of the Internet Protocol Suite, the set of network protocols used for the Internet. With UDP, computer applications can send messages, in this case referred to as datagrams, to other hosts on an Internet Protocol (IP) network without requiring prior communications to set up special transmission channels or data paths.

5. DHCP: Dynamic Host Configuration Protocol. It is a computer networking protocol used by hosts (DHCP clients) to retrieve IP address assignments and other configuration information. DHCP uses a client-server architecture. The client sends a broadcast request for configuration information. The DHCP server receives the request and responds with configuration information from its configuration database.

6. HTML: Hypertext Markup Language. Web page code that defines how a page appears in the web browser.

7. HTTP: Hypertext Transfer Protocol. Connects local web browser to a web server, typically using port 80.

8. HTTPS: Hypertext Transfer Protocol (Secure). Combines HTTP and SSL to establish a secure connection. Uses port 443 by default. Web sites using this protocol start with HTTPS:// and usually show a padlock in the browser. Typically used for authentication and ecommerce.

9. SSL: Secure Sockets Layer. Secures network traffic by using, among other things, encryption and server authentication. Typically used for authentication and ecommerce. Often replaces telnet for secure remote administration of servers and network devices.

10. Telnet: Teletype Network. Protocol used in the command-line tool of the same name. Useful for remote administration of servers, clients, and network devices such as routers. Communicates in unsecured plain text.

11. FTP: File Transfer Protocol. Often used to transmit files using an application of the same name. Commonly used to transfer files across the internet between a web server and Windows hosts. Flexible in that file transfers can occur between differing operating systems.

12. DNS: Domain Name System (Not a real protocol). A service that resolves host names to IP addresses. Web browsers accessing transparently connect to the IP address that was resolved by a DNS server. For example, DNS servers on the Internet resolve to

13. SMTP: Simple Mail Transfer Protocol. SMTP sends email to one or more recipients. Not listed in exam objectives, but of equal importance, is POP3 - Post Office Protocol (v3). This protocol downloads inbound email messages and usually using port 25

14. IMAP: Internet Message Access Protocol. It is used for accessing email on a remote server from a local client. Whereas POP3 downloads email messages, IMAP instantly accesses email stored on a server.

15. POP3: Post Office Protocol 3. It is an application-layer Internet standard protocol used by local e-mail clients to retrieve e-mail from a remote server over a TCP/IP connection. POP and IMAP (Internet Message Access Protocol) are the two most prevalent Internet standard protocols for e-mail retrieval. Virtually all modern e-mail clients and servers support both. The POP protocol has been developed through several versions, with version 3 (POP3) being the current standard.

16. PPP: Point-to-Point Protocol. It is a data link protocol commonly used to establish a direct connection between two networking nodes. It can provide connection authentication, transmission encryption privacy, and compression. PPP is used over many types of physical networks including serial cable, phone line, trunk line, cellular telephone, specialized radio links, and fiber optic links such as SONET. Most Internet service providers (ISPs) use PPP for customer dial-up access to the Internet.

17. SSH: Secure Shell Remote Protocol. is a network protocol that allows data to be exchanged using a secure channel between two networked devices. Used primarily on GNU/Linux and Unix based systems to access shell accounts, SSH was designed as a replacement for Telnet and other insecure remote shells, which send information, notably passwords, in plaintext, rendering them susceptible to packet analyzation. The encryption used by SSH provides confidentiality and integrity of data over an insecure network, such as the Internet.

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