Communicating on a Network - Page 3

As the individual parcels are epitomized from the divided information every layer adds data to the bundle in whats called a header. This header is known as a PDU or Protocol

Data Unit : The header or PDU has vital data that is expected to get the parcel from point A to point B. One vital bit of data that is contained in the PDU headers is the source and destination addresses.

OSI Layer	TCP/IP Layer	PDU
7 Application	Application	Data
6. Presentation		Data
5. Session		Data
4. Transport	Transport	Segment
3. Network	Internet	Packet
2. Data Link	Network Access	Frame
1. Physical		Bits

The addressing that is put into the header of the packets is very important because as the packets travel across the network and encounter networking devices, the devices will strip off the different header addresses which helps send the data to the proper destination.

Layer 7 – Application – Application Data
Layer 6 – Presentation – Formatting Data
Layer 5 – Session – Control Data
Layer 4 – Transport – Source and Destination Service - Port Numbers
Layer 3 – Network – Source and Destination Logical Addresses – IP addresses
Layer 2 – Data Link – Source and Destination Physical Addresses – MAC addresses
Layer 1 – Physical – Encoding, Timing and Bit Sequence

Source and destination MAC locations handle the conveyance of parcels to has on a neighborhood. Each NIC or system interface card has an exceptional MAC address and utilizing Ethernet, bundles are conveyed at the Network Access layer of the TCP/IP model. At this layer the PDU is known as a casing and the source and destination locations distinguish a solitary host. The Frame is peeled off and the bundle is moves to the Network or Internet Layer. The MAC location is frequently called the physical location in light of the fact that it is blazed into the NIC and not regularly designed through programming.

Source and destination IP locations handle the conveyance of parcels to the right system host. For TCP/IP organizing each host must have an IP address which effectively recognizes the system they are on and the host number they possess in that system. Switches have the capacity to peruse the source and destination addresses in the layer 3 bundle header and forward the parcel to the right system. Later a switch will encourage the conveyance of the parcel to the right host NIC by method for the Layer 2 MAC address.

Source and destination ports distinguish the right application or administration that has made the appeal. For example a port 80 appeal would imply that a page is asked for rather than an email which would be port 25.

The layered conventions, addresses, and source and destination locations are exceptionally unique on the grounds that when we ask for a website page with a web program we don't see all the conventions and system layers at work. We don't see singular bundles only a completed page in our program. To help make these conventions and layers more solid you can catch the parcels as they land at your PC and look inside the changed layer headers. To do this you have to utilize a system called Wireshark. Wireshark is exceptionally convenient 'parcel sniffer,' and is a free program to download. See my short feature exercise for a fast introduction on the best way to utilize it.