Addressing, packets and protocols
What are their purposes?
What is a protocol and what is its purpose?
What is a packet and what is its purpose?
What is a MAC Address and what is its purpose?
MAC addresses are 12-digit hexadecimal numbers (48 bits in length). By convention, MAC addresses are usually written in one of the following two formats:
The first half of a MAC address contains the ID number of the adapter manufacturer. These IDs are regulated by an Internet standards body (see sidebar). The second half of a MAC address represents the serial number assigned to the adapter by the manufacturer. In the example,00:A0:C9:14:C8:29
The prefix 00A0C9 indicates the manufacturer is Intel Corporation.
Recall that TCP/IP and other mainstream networking architectures generally adopt the OSI model. In this model, network functionality is subdivided into layers. MAC addresses function at the data link layer (layer 2 in the OSI model). They allow computers to uniquely identify themselves on a network at this relatively low level.
MAC AddressingThere is no attachment cost to devices that connect to the network. The policy is set on a router or switch, and the equipment attached either is permitted or it is not. The person attaching the equipment has nothing to do.
The two parties of the communication don't have to use a pre-established route to send data, data are simply break up into packets and sent through different routes to the destination. you may use also some error control to resend data parts that didn't reach the destination.
PacketIt takes longer than other methods to transfer data. In most cases this will be fairly insignificant but it can be a factor when dealing with real-time video and require additional technology to obtain the required quality.
It is easy to spoof.
Because of the broadcast nature of Ethernet and particularly wireless Ethernet an advisory can sit on the wire and just listen to traffic to and from permitted MAC addresses. Then, the advisory can change his MAC address to a permitted one, and in most cases obtain access to the network.