Shulou(Shulou.com)06/01 Report--

Agreement

A protocol is a collection of rules that must be followed by both parties to control the exchange of information.

Three elements of protocol: syntactic and semantic synchronization

Computer network architecture refers to the layering of the computer network, the functions that each layer should have, and the collection of protocols used in each layer.

Layering:

Only when the problems of the lower layer are solved, can the upper layer be realized. The n layer is the user of layer 1 and the service provider of layer 1. Not only use the service industry provided by n-tier, but also briefly use the services provided by n-tier 1 for nomic 1 layer.

Various protocols must be followed when communicating between peer-to-peer communication entities.

Peer layers cannot interact directly except for the physical layer.

The interface tries the place where the adjacent layers interact in the network hierarchy.

So protocol is a horizontal concept and service is a vertical concept.

The principle of layering:

The functions of each floor should be clear and independent of each other.

The interface between layers should be clear and the amount of information across the interface should be less.

The number of layers should be moderate.

Open systems interconnection model OSI/RM (a model that strives to achieve perfection) but because the market is preempted by TCP/IP, it is limited to theory.

Seven levels of self-directed downward

Application layer

Presentation layer

Session layer

Transport layer

Network layer

Data link layer

Physical layer

At the same time, people's task OSI/RM is the cause of failure.

OSI experts lack practical experience, lack of business drivers.

The implementation of OSI protocol is too complex and inefficient.

The development cycle of OSI standard is too long, so that the equipment can be put on the market for a long time.

The hierarchical division of OSI is not reasonable, and some functions will appear in multiple levels.

Due to some shortcomings, some layers are merged to form a five-tier architecture.

The application layer directly provides services for users' application processes, and there are many protocols, such as Hypertext transfer Protocol, http, simple Mail transfer Protocol, smtp, and so on.

The transport layer is responsible for providing services for communication between processes in the two hosts TPC transmission control protocol UDP user control protocol

The transport layer has the function of multiplexing in the sender, and multiple applications use the services of the transport layer at the same time. There is a sharing function at the receiving end.

The network layer provides packet transport services for different hosts on the network (that is, finding a way to transmit a packet from the source host to the destination host. Note that the transport layer is from application to application.) the protocol is the Internet protocol IP

The basic unit of network layer transmission is packet.

The data link layer adds the packet encapsulation layer frame from the upper layer to the front of the packet with a head and a tail.

The transmission unit of the physical layer is that bite transmits the bit stream transparently without taking any measures, simply sending the bit stream.

In order to keep the frame of the sender and the receiver consistent, several bytes are inserted in front of it.

Entity: any hardware or software process that can send and receive information

Service access point (SAP); the place where two adjacent layers exchange information is that there is more than one interface between the adjacent layers.

Protocol data Unit (PDU): n-layer data plus n-layer pci

Protocol Control Information (PCI):

TCP\ IP architecture

Contains four levels of top-down inclusion

The application layer is the same as the five-layer model

The transport layer is the same as the five-layer model.

The Internet layer is responsible for independently sending packets from the source host to the mapping host to provide the best routing and switching functions for the packet.

For the sender, the network access layer

He is responsible for receiving ip packets delivered from the network layer and wrapping the ip packets in frames that are sent over the underlying physical network.

For the recipient

He is responsible for receiving data frames from the underlying physical network, stripping out ip packets and handing them over to the network layer.

When forwarding, the router uses only the Internet layer instead of the transport layer and the application layer.

TCP/IP protocol stack

There are many smto http ftp snmp RIP protocols in application layer.

The transport layer is connected with a tcp udp

Network interconnection layer ip protocol and icmp igmp arprarp

Ip can provide services for a wide variety of applications everything is ip

The difference between tcp/ip and osi/rm

The departure of the two is different.

Deal with the relationship between levels differently.

Different considerations for the interconnection of heterogeneous networks

Whether to attach equal importance to connection-oriented and connectionless services

The application layer application process sends data to the application layer and goes through the encryption and packaging of various protocols. In addition, the header of the application layer forms the PDU of PDU transmission to the application layer of the next layer, plus the header of the transport layer. The message of the network layer, called the transport layer, is sent to the network layer. Together with the header of the network layer, the ip Datagram packet (sending packets between hosts) is formed. The data link layer packet is transmitted to the data link layer. Plus the head and tail form the data link layer frame the physical layer the data link layer sends the physical layer to insert characters in front of it, and a bit stream is sent to the physical media

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