determine ip and mac header information for a data packet

#Determine ip and mac header information for a data packet mac#

However, when there is a need to test between different networks or across the Internet, a transmission tester that can generate IP packets is required.

#Determine ip and mac header information for a data packet mac#

Layer 2 testing is performed with frames using MAC addresses which are unique to every network device, so as long as the main and remote units of the tester are on the same LAN, the network will ensure they can communicate with each other. Some are limited to operating on Layer 2 networks (LANs) and these may provide helpful as no network configuration process is required to perform prior testing. However, different testers operate on different types of networks. Different data transmission testers may appear very similar in appearance and function because they test the ability of networks to transmit data without errors. The differences between frames and packets are important when choosing Ethernet test equipment for data and performance testing. Once inside a network, intra-network (LAN) data forwarding is handled by Layer 2 switches that read the MAC address of the frame to forward it to the destination device where the Ethernet controller extracts the data payload completing the process of transferring information between devices on different networks. Layer 3 packets allow routers to provide inter-network data transmission (Internet) using IP addresses that identify the network and the temporary address of the device on the network. A router interconnects small networks (LANs) together allowing for information exchange on a much larger scale using IP addresses for packet forwarding instead of MAC addresses. Packets are created at Layer 3 of the network and allow information to be exchanged between different LANs, typically via routers. For example, the IP address of a tablet will change each time it is connected to a different Wi-Fi network. Whereas MAC addresses of a network devices are unique and permanent, IP addresses are usually temporally assigned to a network device and change as the device connects to different networks. Much like the example where the inter-department envelope needs to placed inside a postal envelope to send it to a different office, an Ethernet frame is encapsulated with additional information to create an IP packet.

To send data to a device on a different network or to an internet server, a frame must be built into a packet. Like inter-department mail, a frame cannot be sent outside of the local/private network onto the internet because it does not have the proper address. Remember - all of this is happening on Layer 2 switches in the LAN. If the cable is connected to another switch, the next switch will repeat the lookup and forward process until the frame reaches the intended destination.

If the cable is connected directly to the destination device the transmission is complete. The switch will forward the frame to the physical port determined by the lookup table. The lookup table tells the switch which physical port, i.e., RJ45 port, is associated with the device whose MAC address matches destination address of the frame. The frame is sent onto the network where an Ethernet switch checks the destination address of the frame against a MAC lookup table in its memory. This is an ID number that is unique to every Ethernet device in the entire world.įrames are generated at Layer 2 of the TCP/IP stack by the network interface device with a payload size that depends on the type of data being transmitted.

Instead of a name and department, the source and destination address of a frame are the MAC (Media Access Controller) address of a computer, tablet, IP Phone, IoT device, etc. It is a container for data with a source and destination address to deliver information, called the payload, between two locations on the same network. To send the contents to an office outside of the local area, the inter-office envelope will need to be placed inside a postal envelope and labeled with a proper postal address.Īn Ethernet frame works in a similar way. The envelope never leaves the private/local organization and all of the movement is handled by local resources familiar with the environment.Īn inter-office envelope cannot be sent outside of the company because the envelope does not have a mailing address. When the envelope is sent, the mail room recognizes the internal-use envelope, reads the destination name and department, uses a directory to translate that information into a physical location (building/office) and delivers it to the recipient.