Iso/osi network Architecture and TCP/IP protocol model

1. The reference model of Iso/osi has 7 layers , from low to high level: physical layer, Data link layer, network layer, transport layer, Session layer, presentation layer ,

Application Layer . The functions of each layer are:

(1) Physical layer

provides the mechanical, electrical, functional and procedural characteristics required to establish, maintain, and dismantle physical links; Provides information about the transfer of non-structured bit streams on the transport medium

and physical link fault detection instructions. In this layer, the data is not yet organized, only as the original bit-stream or electrical voltage processing, in units of bits.

(2) Data link layer

responsible for the transmission of frame-based data on the line between two adjacent nodes without error, and flow control. Each frame includes a certain amount of data

And some of the necessary control information. Similar to the physical layer, the data link layer is responsible for establishing, maintaining, and releasing connections to the data link. When transferring data, such as

If the receiving point detects errors in the transmitted data, it is necessary to notify the sender to re-send the frame.

(3) Network layer

provides end-to-end switched network data transfer capability for transport layer entities, freeing the transport layer from network transmission such as routing, switching, congestion control, etc.

Details; one or more communication paths can be established, maintained and removed for the transport layer entities, and unrecoverable errors occurring in the transmission of the network are reported.

The network layer consists of the frames provided by the data link layer, which is encapsulated with the network layer header, which contains the logical address information-the source site and the destination site

The network address of the address.

(4) Transport layer

provide transparent and reliable data transmission service for the session layer entity, ensure end-to-end integrity, select the most appropriate service at the network layer, provide

Maintenance and removal of the transport connection function. The transport layer, based on the characteristics of the communication subnet, is the best use of network resources, for the two-end system between the session layer

The ability to establish, maintain, and cancel transport connections and transmit data in a reliable and economical manner. In this layer, the transmitting unit of information is the message.

(5) Session level

provide the function of establishing, maintaining and ending the session connection for the Cooperative presentation layer entity, and the correspondence between the logical name and the physical name of the communication process;

provides session management services.

(6) Presentation layer

provides a set of services for application-layer processes that interpret the meaning of the exchanged information, converting the data to be exchanged from the abstract syntax appropriate for a user to

A transfer syntax suitable for internal use within the OSI system, providing a formatted representation and transformation Data service. Data compression, decompression, encryption and decryption, etc.

Work is the responsibility of the presentation layer.

(7) Application layer

OSI User Services are provided to determine the nature of communication between processes to meet user needs and to provide interface services between the network and the user application software.

In short, the role of each layer:

Physical Layer : transmits the raw data bitstream on the physical media.

Data Link Layer : Divides data into data frames and transmits them in a data frame. There should be a reply, the wrong re-hair.

Network layer : The data is divided into a certain length of grouping, will be grouped through the communication subnet, select a path from the source to upload to the message.

Transport Layer : an efficient, cost-effective, transparent, end-to-end data transfer service that provides no specific network.

Session Layer : Conversations between processes are also known as sessions, and the session layer manages conversations between processes on different hosts.

Presentation Layer : Provides a formatted representation and transformation Data service for the application-tier process.

Application Layer : Provides the means by which applications access the OSI environment.

2. The Iso/osi Reference model corresponds to each layer in the TCP/IP protocol model:

3. Encapsulation and decryption of data:

4. OSI Network architecture layer protocols:

(1) Application layer: TELNET, FTP, TFTP, SMTP, SNMP, HTTP, BOOTP, DHCP, DNS
(2) Presentation layer:
Text: Ascii,ebcdic
Graphics: tiff,jpeg,gif,pict
Voice: Midi,mpeg,quicktime

(3) Session layer: NFS, SQL, RPC, X-windows, ASP (apptalk Session protocol), SCP
(4) Transport layer: TCP, UDP, SPX
(5) Network layer: IP, IPX, ICMP, RIP, OSPF (Open Shortest Path First)
(6) Data link layer: SDLC, HDLC, PPP, STP (Spanning Tree Protocol), Frame Relay
(7) Physical layer: Eia/tia RS-232, Eia/tia RS-449, v.35, RJ-45

5. Common ports (each protocol has a default port)

Iso/osi network Architecture and TCP/IP protocol model