Common TCP/IP Protocols and Ports

Common TCP/IP Protocols and Ports

Here are some of the common TCP/IP protocols and the ports used by them.

1. File Transfer Protocol (FTP) : FTP is one of the most popular file transfer protocols for the Internet and private networks. An FTP server is simple to set up and allows for easy file transfer across systems. FTP control is performed on TCP port 21, while data transport can utilize either TCP port 20 or dynamic ports, depending on the configuration.

FTP uses TCP port 20/21

2. Secure Shell (SSH) : SSH is the primary method used to manage network devices securely at the command level. It is typically used as a secure alternative to Telnet which does not support secure connections.

SSH uses TCP port 22

3. Telnet : Telnet is the primary method used to manage network devices at the command level. Unlike SSH which provides a secure connection, Telnet does not, it simply provides a basic unsecured connection. Many lower level network devices support Telnet and not SSH as it required some additional processing. Caution should be used when connecting to a device using Telnet over a public network as the login credentials will be transmitted in the clear.

Telnet uses TCP port 23

4. Simple Mail Transfer Protocol (SMTP) : SMTP is used for two primary functions, it is used to transfer mail (email) from source to destination between mail servers and it is used by end users to send email to a mail system.

SMTP uses TCP 25

5. Domain Name System (DNS) : The Domain Name System (DNS) is widely used on the public internet and private networks to translate domain names into IP addresses, usually for network routing. DNS is hierarchical, with primary root servers that house databases including the managers of high-level Top Level Domains (TLDs) (such as .com). These various TLD managers then hold information for the second-level domains that are commonly used by individual users (such as thenetworkdna.com). A DNS server can also be configured within a private network to provide private naming services between internal network sites that are not part of the global system.

DNS uses TCP/UDP 53

6. Dynamic Host Configuration Protocol (DHCP) : DHCP is used on networks that do not use static IP address assignment (almost all of them). A DHCP server can be set up by an administrator or engineer with a poll of addresses that are available for assignment. When a client device is turned on it can request an IP address from the local DHCP server, if there is an available address in the pool it can be assigned to the device. This assignment is not permanent and expires at a configurable interval; if an address renewal is not requested and the lease expires the address will be put back into the poll for assignment.

DHCP uses TCP/UDP 67/68

7. Trivial File Transfer Protocol (TFTP) : TFTP offers a method of file transfer without the session establishment requirements that FTP uses. Because TFTP uses UDP instead of TCP it has no way of ensuring the file has been properly transferred, the end device must be able to check the file to ensure proper transfer. TFTP is typically used by devices to upgrade software and firmware; this includes Cisco and other network vendors’ equipment.

TFTP uses UDP 69

8. Hypertext Transfer Protocol (HTTP) : HTTP is one of the most commonly used protocols on most networks. HTTP is the main protocol that is used by web browsers and is thus used by any client that uses files located on these servers.

HTTP uses TCP 80

9. Post Office Protocol (POP) version 3 : POP version 3 is one of the two main protocols used to retrieve mail from a server. POP was designed to be very simple by allowing a client to retrieve the complete contents of a server mailbox and then deleting the contents from the server.

POPv3 uses TCP 110

10. Network Time Protocol (NTP) : One of the most overlooked protocols is NTP. NTP is used to synchronize the devices on the Internet. Even most modern operating systems support NTP as a basis for keeping an accurate clock. The use of NTP is vital on networking systems as it provides an ability to easily interrelate troubles from one device to another as the clocks are precisely accurate.

NTP uses UDP 123

11. NetBIOS : NetBIOS itself is not a protocol but is typically used in combination with IP with the NetBIOS over TCP/IP (NBT) protocol. NBT has long been the central protocol used to interconnect Microsoft Windows machines.

NetBIOS uses TCP/UDP 137/138/139

12. Internet Message Access Protocol (IMAP) : IMAP version3 is the second of the main protocols used to retrieve mail from a server. While POP has wider support, IMAP supports a wider array of remote mailbox operations which can be helpful to users.

IMAP uses TCP 143

13. Simple Network Management Protocol (SNMP) : SNMP is used by network administrators as a method of network management. SNMP has a number of different abilities including the ability to monitor, configure and control network devices. SNMP traps can also be configured on network devices to notify a central server when specific actions are occurring. Typically, these are configured to be used when an alerting condition is happening. In this situation, the device will send a trap to network management stating that an event has occurred and that the device should be looked at further for a source to the event.

SNMP uses TCP/UDP 161/162

14. Border Gateway Protocol (BGP) : BGP version 4 is widely used on the public internet and by Internet Service Providers (ISP) to maintain very large routing tables and traffic processing. BGP is one of the few protocols that have been designed to deal with the astronomically large routing tables that must exist on the public Internet.

BGP uses TCP 179

15. Lightweight Directory Access Protocol (LDAP) : LDAP provides a mechanism of accessing and maintaining distributed directory information. LDAP is based on the ITU-T X.500 standard but has been simplified and altered to work over TCP/IP networks.

LDAP uses TCP/UDP 389

16. Hypertext Transfer Protocol over SSL/TLS (HTTPS) : HTTPS is used in conjunction with HTTP to provide the same services but doing it using a secure connection which is provided by either SSL or TLS.

HTTPS uses TCP 443

17. Lightweight Directory Access Protocol over TLS/SSL (LDAPS) : Just like HTTPS, LDAPS provides the same function as LDAP but over a secure connection which is provided by either SSL or TLS.

LDAPS uses TCP/UDP 636

18.FTP over TLS/SSL : FTP over TLS/SSL uses the FTP protocol which is then secured using either SSL or TLS.

FTP over TLS/SSL uses TCP 989/990