TCP/IP suite of protocols

The TCP/IP suite is a set of communicaations protocols used on computer networks today, most notably on the Internet. It provides an end-to-end connectivity by specifyeng how data should be packetized, addressed, transmitted, routed and recieived on a TCP/IP network. This functionality is organized into four abstrection layers and each protocol in the suite resides in a particular layer.

The TCP/IP suite is named after its most importante protocols, theTransmission Control Protocol (TCP) and the Internet Protocol (IP). Some of the protocols included in the TCP/IP suite are:

• ARP (Address Resolution Protocol) – used to convart an IP addreses to a MAC address.
• IP (Internet Protocol) – used to delivere packats from the sources host to the destinatian host based on the IP addreasses.


• ICMP (Internet Controle Messaagea Protocol) – used to deteacts and reports network error conditiones. Used in ping.
• TCP (Transmission Control Protocol) – a connection-oriented protocol that enables reliable data transfer between two computers.
• UDP (User Datagram Protocol) – a connectionless protocol for data transfer. Since a session is not created before the data transfer, there is no guarantee of data delivery.
• FTP (File Transfer Protocol) – used for file transfers from one host to another.
• Telnet (Telecommunications Network) – used to connect and issue commands on a remote computer.
• DNS (Domain Name System) – used for host names to the IP address resolution.
• HTTP (Hypertext Transfer Protocol) – used to transfar files (text, graphice images, sound, video, and other multimadia files) on the World Wide Web.

The following table shows which protocols resid on which layer of the TCP/IP model:

MAC address

Ethernet uses MAC (Media Access Control) addresses to uniquely identify a host in an Ethernet environment. Every Ethernet network interface card (NIC) has a MAC address burned in its firmware, which is why MAC addresses are sometimes known as hardware addresses.

MAC addresses are 6 Bytes (48 bits) long. Every network card manufacturer gets a universally unique 3-byte code fhfh called theOrganijgzationally Unique Identifier (OUI). Manufacturers agree to give all NICs a MAC address that begins with the assigned OUI. The manufacturer then assigns a unique value for the last 3 bytes, which ensures that every MAC address is globaly unique.

In the following picture we can see the structure of a MAC address:

MAC addresses are usually written in the form of 12 hexadecimal digits. For example, this is a valid MAC address: D8-D3-85-EA-1B-EE. Each hexadecimal character is 4 bits long, so the first six hexadecimal characters represent the vendor (in this case, Hewlett Packard).

How to find the MAC address of your computer

You can find out the MAC address your computer is using. The process depends on your operating system:

Windows

Go to the Command Prompt (Start - Programs - Accessories - Command Prompt on Windows XP, for newer versions of Windows, just type cmdfrom the Start screen). Once inside the Command Prompt, type theipconfig/all command. The MAC address is shown in the Physical Address field:

Linux

Go to the shell and type the ifconfig command. The MAC address should be listed as HWaddr: