tailieunhanh - Practical TCP/IP and Ethernet Networking- P10

Practical TCP/IP and Ethernet Networking- P10: The transmitter encodes the information into a suitable form to be transmitted over the communications channel. The communications channel moves this signal as electromagnetic energy from the source to one or more destination receivers. The channel may convert this energy from one form to another, such as electrical to optical signals, whilst maintaining the integrity of the information so the recipient can understand the message sent by the transmitter | Networking fundamentals 27 TP1 transfer protocol class 1 It assumes a type B subnet that is one that may be unreliable. To deal with this TP1 provides its own error detection along with facilities for getting the sender to retransmit any erroneous packets TP2 transfer protocol class 2 It also assumes a type A subnet. However TP2 can multiplex transmissions so that multiple transport connections can be sustained over the single network connection TP3 transfer protocol class 3 It also assumes a type B subnet. TP3 can also multiplex transmissions so that this protocol has the capabilities of TP1 and TP2 TP4 transfer protocol class 4 It is the most powerful protocol in that it makes minimal assumptions about the capabilities or reliability of the subnet. TP4 is the only one of the OSI transport-layer protocols that supports connectionless service Network layer The network layer is the third lowest layer or the uppermost subnet layer. It is responsible for the following tasks Determining addresses or translating from hardware to network addresses. These addresses may be on a local network or they may refer to networks located elsewhere on an internetwork. One of the functions of the network layer is in fact to provide capabilities needed to communicate on an internetwork Finding a route between a source and a destination node or between two intermediate devices Establishing and maintaining a logical connection between these two nodes to establish either a connectionless or a connection-oriented communication. The data is processed and transmitted using the data link layer below the network layer. Responsibility for guaranteeing proper delivery of the packets lies with the transport layer which uses network layer services Fragmentation of large packets of data into frames which are small enough to be transmitted by the underlying data link layer fragmentation . The corresponding network layer at the receiving node undertakes reassembly of the packet Data link