H.323 (Video) (1720):

H.323 is a protocol that provides a standard for video on an IP network that defines how real-time audio, video, and data information is transmitted. This standard provides signaling, multimedia, and bandwidth control mechanisms. H. 323 uses the RTP standard for communication.

Simple Network Management Protocol (161):

Simple Network Management Protocol (SNMP) collects and manipulates valuable network information. It gathers data by polling the devices on the network from a management station at fixed or random intervals, requiring them to disclose certain information. This protocol can also stand as a watchdog over the network, quickly notifying managers of any sudden turn of events. The network watchdogs are called agents, and when aberrations occur, agents send an alert called a trap to the management station.

SNMP can help simplify the process of setting up a network as well as the administration of your entire internetwork.

Secure Shell (22):

Secure Shell (SSH) protocol sets up a secure Telnet session over a standard TCP/IP connection and is employed for doing things like logging into other systems, running programs on remote systems, and moving files from one system to another. And it does all of this while maintaining a nice, strong, encrypted connection.

Hypertext Transfer Protocol (80):

All those snappy websites comprising a mix of graphics, text, links, and so on the Hypertext Transfer Protocol (HTTP) is making it all possible. It's used to manage communications between web browsers and web servers, and opens the right resource when you click a link, wherever that resource may actually reside.

Hypertext Transfer Protocol Secure (443):

Hypertext Transfer Protocol Secure (HTTPS) is a secure version of HTTP that arms you with a whole bunch of security tools for keeping transactions between a web browser and a server secure. It's what your browser needs to fill out forms, sign in, authenticate, and encrypt an HTTP when you do something online.

Network Time Protocol (123):

This protocol used to synchronize the clocks on our computers to one standard time source (typically, an atomic clock). Network Time Protocol (NTP) works in conjunction with other synchronization utilities to ensure that all computers on a given network agree on the time.

NetBIOS (137-139):

Network Basic Input/output System works only in the upper layers of the OSI model and allows for an interface on separate computers to communicate over a network.

It was first created in the early 1980s to work on an IBM LAN and was proprietary. Microsoft and Novel both created a NetBIOS implementation to allows their hosts to communicate to their servers.

Server Message Block (445):

Server Message Block (SMB) is used for sharing access to files and printers and other communications between hosts on a Microsoft Windows network.

SMB can run on UDP port 137 and 138, and TCP port 137 and 139 using NetBIOS.

Domain Name Service (53):

Domain Name Service (DNS) resolves hostnames specifically, Internet names, such as www.bookofnetwork.com to their corresponding IP addresses.

You don't have to use DNS; you can just type in the IP address of any device you want to communicate with. An IP address identifies hosts on a network and the Internet as well.

Dynamic Host Configuration Protocol/Bootstrap Protocol (67/68):

Dynamic Host Configuration Protocol (DHCP) assigns IP addresses to hosts with information provided by a server. It allows easier administration and works well in small to even very large network environments. Many types of hardware can be used as a DHCP server, including routers.

There is a lot of information a DHCP server can provide to a host when the host is requesting an IP address from the DHCP server. Here's a partial list of the information a DHCP server can provide:

  • IP address
  • Subnet mask
  • Domain name
  • Default gateway (routers)
  • DNS
  • Windows Internet Naming Service (WINS) information

The following is the four-step process a client takes to receive an IP address from a DHCP server:

1) The DHCP client broadcasts a DHCP Discover message looking for a DHCP server

(port 67).

2) The DHCP server that received the DHCP Discover message sends a unicast DHCP

Offer message back to the host.

3) The client then broadcasts to the server a DHCP Request message asking for the

offered IP address and possibly other information.

4) The server finalizes the exchange with a unicast DHCP Acknowledgment message.