note01-Computer Network

1. Basic overview

Three networks: Telecommunication network, CATV Network, computer network (connect & share)

Terminal->z local isp->x area ixp->y backbone ISP

Means of communication: C/S, peer (that is, the client is also the server can share each other's resources)

Interaction Type:

Circuit interaction (n-Phones need n (N-1)/2 Dedicated physical connection line-built-up, bit-stream transmission from source to final release)

Message exchange (complete message to adjacent Node B storage and check table forward next node C)

Packet interaction (a single P1 packet of messages arrives at the neighboring Node B store and forwards the next node C P2 and can reach adjacent Node B)

Performance Index:

Rate (number of bits of digital signal transmitted in a unit of time B/s)

Bandwidth (communication lines allow the frequency band width of the analog signal to be higher faster)

Throughput (amount of data over a network, channel, interface, per unit of time)

Delay (send b/s), propagation m/(M/s), processing, queuing delay)

Latency bandwidth (propagation delay * Bandwidth indicates the number of bits already sent on the link when the first bit reaches the end)

Round Trip Time Rtt (from the time the data is sent to the endpoint to confirm receipt and send confirmation)

Utilization (d/(1-U) network Idle latency divided by 1-utilization)

Architecture OSI layer Seven and TCP/IP layer four:

TCP/IP four-tier architecture:

The Application layer Protocol (HTTP\SMTP\FTP..ETC) defines the rules of communication and interaction between application processes, and data units are messages;

The task of the Transport layer is to provide a General Service for the application process communication between two hosts, the TCP protocol is link-oriented, reliable, the data unit is the message segment, UDP is not linked, the best effort is transmitted, and the data unit user data is reported;

The network layer is responsible for the host communication of the packet switching networks, transmitting the packets or packets of the packet or user data in the transmission layer, using the IP protocol, and transmitting the IP datagram;

The data link layer encapsulates the IP data into frames (including error, address and other control information), and transmits in neighboring nodes;

The physical layer transmits the frame data in the form of bit stream;

note01-Computer Network