Común de protocolos de red Resumida
Computer networks play a vital role in most of the organizations. Networks provide a very rapid method for sharing and transferring files. To effectively access network resources, you must understand the Network protocol services. Here is the summary of some common networking protocols:
Transmission Control Protocol (TCP) is a reliable, connection-oriented protocol operating at the transport layer of the OSI model. It provides a reliable packet delivery service encapsulated within the Internet Protocol (IP). TCP guarantees the delivery of packets, ensures proper sequencing of data, and provides a checksum feature that validates both the packet header and its data for accuracy. If the network corrupts or loses a TCP packet during transmission, TCP is responsible for retransmitting the faulty packet. It can transmit large amounts of data. Application-layer protocols, such as HTTP and FTP, utilize the services of TCP to transfer files between clients and servers.
File Transfer Protocol (FTP) is a primary protocol of the TCP/IP protocol suite. It is used to transfer text and binary files between computers over a TCP/IP network. FTP uses TCP ports 20 and 21 for communication.
User Datagram Protocol (UDP) is often used for one-to-many communications, using broadcast or multicast IP datagrams. Microsoft networking uses UDP for logon, browsing, and name resolution. UDP is a connectionless and unreliable communication protocol. It does not guarantee delivery, or verify sequencing for any datagram. UDP provides faster transportation of data between TCP/IP hosts than TCP.
Dynamic Host Configuration Protocol (DHCP) is a TCP/IP standard used to dynamically assign IP addresses to computers, so that they can communicate with other network services. It reduces the complexity of managing network client IP address configuration. A DHCP server configures DHCP-enabled client computers on the network. It runs on servers only. It also provides integration with Windows Active Directory directory service. DHCP uses ports 67 and 68 for communication.
Trivial File Transfer Protocol (TFTP) is a file transfer protocol, with the functionality of a very basic form of File Transfer Protocol (FTP). TFTP can be implemented in a very small amount of memory. It is useful for booting computers such as routers which did not have any data storage devices. It is used to transfer small amounts of data between hosts on a network, such as IP phone firmware or operating system images when a remote X Window System terminal or any other thin client boots from a network host or server. The initial stages of some network based installation systems (such as Solaris Jumpstart, Red Hat Kickstart and Windows NT's Remote Installation Services) use TFTP to load a basic kernel that performs the actual installation. TFTP uses UDP port 69 for communication.
Domain Name System (DNS) is a hierarchical naming system used for locating domain names on private TCP/IP networks and the Internet. It provides a service for mapping DNS domain names to IP addresses and vice versa. DNS enables users to use friendly names to locate computers and other resources on an IP network. TCP/IP uses IP addresses to locate and connect to hosts, but for users, it is easier to use names instead of IP address to locate or connect to a site. For example, users will be more comfortable in using the host name www.uCertify.com rather than using its IP address 66.111.64.227. DNS uses TCP and UDP ports 53 for communication.
Hypertext Transfer Protocol (HTTP) is a client/server TCP/IP protocol used on the World Wide Web (WWW) to display Hypertext Markup Language (HTML) pages. HTTP defines how messages are formatted and transmitted, and what actions Web servers and browsers should take in response to various commands. For example, when a client application or browser sends a request to the server using HTTP commands, the server responds with a message containing the protocol version, success or failure code, server information, and body content, depending on the request. HTTP uses TCP port 80 as the default port.
HTTPS is an encrypted form of the HTTP protocol, used to protect end users from submitting private information to a rogue server impersonating another server. HTTPS is designed to coexist with the messaging model of HTTP and to be easily integrated with HTTP applications. It does not require client-side public key certificates, as it supports symmetric key-only operation modes. This is significant because it means that spontaneous private transactions can occur without requiring individual users to have an established public key. Strictly speaking, HTTPS is not a separate protocol, but refers to use of ordinary HTTP over an encrypted Secure Sockets Layer (SSL) or Transport Layer Security (TLS) connection. This ensures reasonable protection from eavesdroppers and man-in-the-middle attacks, provided that adequate cipher suites are used and that the server certificate is verified and trusted. HTTPS uses port 443 for communication.
Address Resolution Protocol (ARP) is a network maintenance protocol of the TCP/IP protocol suite. It is responsible for the resolution of IP addresses to media access control (MAC) addresses of a network interface card (NIC). The ARP cache is used to maintain a correlation between a MAC address and its corresponding IP address. ARP provides the protocol rules for making this correlation and providing address conversion in both directions. ARP is limited to physical network systems that support broadcast packets.
Session Initiation Protocol (SIP), designed by Henning Schulzrinne and Mark Handley in 1996, is a signaling protocol, widely used for setting up and tearing down multimedia communication sessions such as voice and video calls over the Internet (VoIP). Other feasible application examples include video conferencing, streaming multimedia distribution, instant messaging, presence information and online games. The protocol can be used for creating, modifying, and terminating two-party (unicast) or multiparty (multicast) sessions consisting of one or several media streams. The modification can involve changing addresses or ports, inviting more participants, adding or deleting media streams, etc. The SIP protocol is a TCP/IP-based Application Layer protocol. Within the OSI model, it is sometimes placed in the session layer. SIP is designed to be independent of the underlying transport layer; it can run on TCP, UDP, or SCTP. It is a text-based protocol, sharing many elements of the Hypertext Transfer Protocol (HTTP), upon which it is based, allowing for easy inspection by administrators. SIP clients typically use TCP or UDP (typically on port 5060 and/or 5061) to connect to SIP servers and other SIP endpoints.
Real-time Transport Protocol (RTP), developed by the Audio-Video Transport Working Group of the IETF and first published in 1996, defines a standardized packet format for delivering audio and video over the Internet. RTP is used extensively in communication and entertainment systems that involve streaming media, such as telephony, video teleconference applications and web-based push to talk features. For these, it carries media streams controlled by H.323, MGCP, Megaco, SCCP, or Session Initiation Protocol (SIP) signaling protocols, making it one of the technical foundations of the Voice over IP industry. RTP is usually used in conjunction with the RTP Control Protocol (RTCP). When both protocols are used in conjunction, RTP is usually originated and received on even port numbers, whereas RTCP uses the next higher odd port number. RTP and RTCP typically use unprivileged UDP ports (1024 to 65535).
Secure Shell (SSH) is a protocol that provides strong authentication and secure communications over unsecured channels. It uses public key encryption as the main method for user authentication. SSH secures connections over the Internet by encrypting passwords and other data. It also protects networks against IP spoofing, packet spoofing, password sniffing, and eavesdropping. SSH uses TCP port 22 as the default port and operates at the application layer.
Post Office Protocol version 3 (POP3) 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. The design of POP3 and its procedures supports end-users with intermittent connections (such as dial-up connections), allowing these users to retrieve e-mail when connected and then to view and manipulate the retrieved messages without needing to stay connected. Although most clients have an option to leave mail on server, e-mail clients using POP3 generally connect, retrieve all messages, store them on the user's PC as new messages, delete them from the server, and then disconnect. POP3 works over a TCP/IP connection using TCP on network port 110. E-mail clients can encrypt POP3 traffic using TLS or SSL.
According to the NTP distribution document, "The Network Time Protocol (NTP) is used to synchronize the time of a computer client or server to another server or reference time source, such as a radio or satellite receiver or modem. It provides accuracies typically within a millisecond on LANs and up to a few tens of milliseconds on WANs relative to Coordinated Universal Time (UTC) via a Global Positioning Service (GPS) receiver, for example. Typical NTP configurations utilize multiple redundant servers and diverse network paths in order to achieve high accuracy and reliability."
Internet Message Access Protocol (IMAP or IMAP4) is a prevalent Internet standard protocol for e-mail retrieval. It is an application layer Internet protocol operating on port 143 that allows a local client to access e-mail on a remote server. IMAP supports both connected (online) and disconnected (offline) modes of operation. E-mail clients using IMAP generally leave messages on the server until the user explicitly deletes them. This and other facets of IMAP operation allow multiple clients to access the same mailbox.
Telnet (Telecommunication network) is a network protocol used on the Internet or local area networks to provide a bidirectional interactive communications facility. Typically, Telnet provides access to a command-line interface on a remote host via a virtual terminal connection which consists of an 8-bit byte oriented data connection over the Transmission Control Protocol (TCP). User data is interspersed in-band with TELNET control information. Typically, the Telnet protocol is used to establish a connection to Transmission Control Protocol (TCP) port number 23.
Simple Mail Transfer Protocol (SMTP) is a protocol for sending e-mail messages between servers. E-mailing systems use this protocol to send mails over the Internet. SMTP works on the application layer of the TCP/IP or OSI reference model. However, e-mail clients require POP or IMAP to retrieve mails from e-mail servers. SMTP uses TCP port 25 for communication.
Simple Network Management Protocol (SNMP) is a part of the TCP/IP protocol suite, which allows users to manage the network. SNMP is used to keep track of what is being used on the network and how the object is behaving. SNMP uses UDP port 161 for communication.
Internet Control Message Protocol (ICMP) is an integral part of IP. It is used to report an error in datagram processing. The Internet Protocol (IP) is used for host-to-host datagram service in a network. The network is configured with connecting devices called gateways. When an error occurs in datagram processing, gateways or destination hosts report the error to the source hosts through the ICMP protocol. The ICMP messages are sent in various situations, such as when a datagram cannot reach its destination, when the gateway cannot direct the host to send traffic on a shorter route, when the gateway does not have the buffering capacity, etc.
Internet Group Management Protocol (IGMP) is a communication protocol that multicasts messages and information among all member devices in an IP multicast group. However, multicast traffic is sent to a single MAC address but is processed by multiple hosts. It can be effectively used for gaming and showing online videos. IGMP is vulnerable to network attacks.
Transport Layer Security (TLS) is a cryptographic protocol that provides security and data integrity for communications over networks such as the Internet. TLS and SSL encrypt the segments of network connections at the Transport Layer end-to-end. Several versions of the protocols are in wide-spread use in applications like web browsing, electronic mail, Internet faxing, instant messaging, and voice-over-IP (VoIP). The TLS protocol, an application layer protocol, allows client/server applications to communicate across a network in a way designed to prevent eavesdropping, tampering, and message forgery. TLS provides endpoint authentication and communications confidentiality over the Internet using cryptography.
Given below are some of the important TCP and UDP ports that a network administrator is supposed to be familiar with:
| TCP Ports | Protocols |
|---|---|
| 20 | FTP |
| 21 | FTP |
| 22 | SSH |
| 23 | Telnet |
| 25 | SMTP |
| 53 | DNS |
| 80 | HTTP |
| 110 | POP3 |
| 123 | NTP |
| 143 | IMAP |
| 443 | HTTPS |
| UDP Ports | Protocols |
|---|---|
| 53 | DNS |
| 67 | BOOTPS/DHCP |
| 69 | TFTP |
| 161 | SNMP |
These protocols use their respective ports as the default configuration.
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