| 10.2 |  | Overview of Transport Layer Ports |
| 10.2.6 |  | Comparison of MAC addresses, IP addresses, and port numbers |

| These three methods of addressing are often confusing, but this can be avoided if the addresses are explained in reference to the OSI model. Port numbers are located at the transport layer and are serviced by the network layer. The network layer assigns the logical address (IP address) and is then serviced by the data link layer which assigns the physical address (MAC address). A good analogy can be made with a normal letter. The address on a letter consists of a name, street, city, and state. These can be compared to the port, MAC, and IP address used for network data. The name on the envelope would be equivalent to a port number, the street address is the MAC, and the city and state is the IP address. Multiple letters can be mailed to the same street address, city and state, but contain different names on the letters. For instance, two letters could be mailed to the same house with one addressed to “John Doe” and the other to “Jane Doe”. This is analogous to multiple sessions with different port numbers.