Different data transmission testers may appear very similar in appearance and function because they test the ability of networks to transmit data without errors. However, different testers operate on different types of networks. 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.
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.
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. When testing at Layer 3 and higher, configuring the two handsets to locate each other can be daunting. Because IP addresses are not unique to devices in different networks, users need to have a detailed understanding of the network at each location to ensure the tester handsets can communicate and not create conflicts with other devices on the network.
To summarize, Layer tests are best used for testing bandwidth between networks WANs and Layer 2 tests are best for testing bandwidth between devices within the same network LANs. Here are the latest Insider stories. More Insider Sign Out. On the other hand, Network layer performs fragmentation of the data and create smaller chunks known as packets. Basis for comparison Frame Packet Basic Frame is the data link layer protocol data unit. Packet is the network layer protocol data unit.
Source and destination IP address. Correlation Segment is encapsulated within a packet. Packet is encapsulated within a frame. A Frame can be defined as a data unit used in Data Link layer. A frame is consist of markers which depicts the start and end of the packet and addresses for sending and receiving.
A particular example of a frame is the Ethernet frame. Like Article. Next Stop and Wait protocol, its problems and solutions. Recommended Articles. Difference between Multiprogramming, multitasking, multithreading and multiprocessing.
Article Contributed By :. Easy Normal Medium Hard Expert. Writing code in comment? Please use ide. Load Comments. Irrespective of whether you are talking about network layer, transport layer or physical layer, the term PDU is generic and applies to all.
Of Course different layers add different fields on top of data, but they can still be called PDUs. Being said that, according to OSI reference layered architecture, below is what is widely accepted.
Network communication is actually message oriented. As far as an application is concerned, the requirement might be to send a file to another machine on the network. Or download a particular file from a remote server. But you cannot send a file in one single message. You have to basically slice it out to different chunks and then send it out. Although applications can be programmed to do this, its going to be a lot of overhead for programmers. Applications should then have logic about which chunk is sent, and acknowledged and which is remaining to be sent, which chunk needs to be resent etc.
Also you will then have to come with a particular size for each chunk that the application will create. So basically more tedious job on application programming. This is what exactly TCP is capable of. So basically applications will send a stream of bytes to TCP Without worrying at all about size and chunks. Its nothing but data stream in bytes , and TCP will take care of slicing it up and sending in discrete message form. TCP segments can do multiple things at the same time.
We know the fact that byte stream data provided by applications are sliced into different chunks called segments and are delivered to receiver separately. One single segment carry data along with acknowledgement of another segment. A TCP segment is made of different fields which carry different meanings. This means a considerable amount of space in each segment is used for conveying different functions and controls called headers. Data chunk is wrapped by these headers.
Generally each segment has a dedicated 20 bytes section only for the headers. To have a quick look into a segment, the best program available is tcpdump. One one terminal you can fire up the command sudo tcpdump -vvv -n host www. The above two lines show the segment headers. All TCP segments will have similar looking headers.
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