pdu osi

I. Role of the transport layer 1. Track sessions Because each host may have multiple processes for communication, the transport layer needs to send each data segment to the corresponding process. This can also be understood by adding the source and

Application layer: An application that can generate network trafficPresentation layer: Encrypt and compress binary ASCII to represent contentSession Layer: Server and client establish connections and maintain session communication

Physical Layer: provides physical links for the previous layer, and specifies the mechanical and electrical properties between communication nodes, such as the type of specified cables and connectors, and the voltage transmitted. At this layer, bit

Well, a lot of things are summed up by their own feelings, there is a wrong point of view please help point out. Thank youThe version on the physical layer textbook is:The function of physical layer is to provide the establishment of the circuit on

  (1) physical layer: transmits the original data bit stream over the communication channel.   (2) data link layer: Let the sender split the input data into data frames and then transmit these data frames in sequence. Then, a traffic adjustment

Tags: OSI seven layer model, TCP, UDP, ARPOne OSI seven-layer model: 1 OSI Reference Model produces background:Since the 1960s, the computer network has been growing rapidly. In order to dominate in the field of data communication networks, major manufacturers have launched their own network architecture and standards, such as IBM's Sna,novell ipx/spx agreement,

octet ). Version-Version/Protocol ID Extension identifies ISO 8473. Lifetime-PDU Lifetime indicates the remaining Lifetime of the PDU, in units of 500 milliseconds. Flags-three tags: License Segmentation Permitted), More Segments), Error Report ). The Type-Type code field identifies the protocol data unit Type, which may be: Data PDU or error report

number.The port number is related to the protocol, the TCP/IP transport Layer Two protocols TCP and UDP are completely independent of the two software modules, so the respective port numbers are also independent of each other, ports are often referred to as protocol port (Protocol port), referred to as port.　　The port is represented by a 16-bit number, and its range is 0~65535,1024 the port number below it to the predefined service. For example, HTTP uses port 80.Data EncapsulationOne computer

will make each layer of the protocol too complex.(2) The number of layers is too many, it will be more difficult to describe and synthesize the functions of each layer of systems engineering tasks. 5, the formation of computer network system structure In 1974, IBM in the United States announced the SNA for the System network architecture it developed(System Network Architecture). It is one of the most widely used network architecture in the world. Soon some big companies are rolling out their o

As the DICOM Standard itself is named, the main problem to be solved by DICOM is network transmission, that is, in various network hardware and software environments, how can medical images be reliably and efficiently transmitted to the desired target computer. To this end, the DICOM standard adopts the policy of adding support for medical images on the basis of a mature and standardized network environment, rather than starting from the minimum layer, in this way, existing network hardware and

wrap the data together. Each layer communicates only with the peer layer on the receiving device.In order to communicate and exchange information, each layer uses the PDU (PROTOCAOL Data Unit, Protocol Unit). PDUs contain control information that is added to the data at each level. These control information is usually added to the header in front of the data field, but may also be added to the trailer.Each layer of the

Tags: network LinuxInternetOSI (Definition of the International Organization for Standardization Network, Open Systems Interconnection) ISO (International Organization for Standardization)OSI Network Model tieringLower level services for the upper layer7 Application Layer (application): A range of application software6 presentation layer (PRESENTION): formatted data, encryption, compression, etc.5 Session Layer: Establish, manage, and terminate sessio

unreliable transmission protocol. however, it does not need to establish connections, there is no data validation and retransmission mechanism, and the timeliness is high. UDP can be used for video conferencing, video on demand, instant voice communication, instant chat, and so on. Network Layer: IP: Internet protocol. ICMP: Internet Control Packet protocol. IGMP: Internet group management protocol. 3. Data encapsulation Data must be packaged for transmission. The process of packaging with a s

relationship between the OSI layers and the communication between two (n) layersMust pass through the next layer (N-1) layer entity, not beyond the levelAnd TCP/IP can bypass the adjacentThe next layer directly uses the services provided by lower layersTherefore, it reduces unnecessary overhead and improves the Protocol efficiency. ③ OSI has a model and a protocol, which is suitable for theoretical discu

a mock web browser, type www.example.com carriage return, and then minimize the emulated browser window. Step four: Run the simulation environment In the Analog Panel control mode section, click the Auto Play button. Observe events between the PC and the server, and events added to the events list. These represent the requests and decisions of the PC. If a roundtrip PDU packet has a check mark on the envelope after it arrives on the PC, the requested

1. Abbreviations 1) sndcp: subnetworkdependence converage protocol, subnet-related aggregation Protocol 2) nsapi: Network Layer Service Access Point identifier. The identifier of the network layer service access point is actually an index of the PDP context of the service using the sndcp layer, the Service Access Point provided by sndcp to the upstream layer; 3) SAPI: the service access point provided by LLC to the upstream Layer 3）Qos：quality ofservice 4）BSS：Base StationSystem 5）SGSN：Service G

emphasized that the OSI reference model is not a description of the implementation, but rather a conceptual framework for the development of standard machines. In the OSI, only a variety of protocols are achievable, and devices in the network can be interconnected only if they are consistent with the OSI and related protocols. The TCP/IP model focuses on relate

, protocol family. It also includes HTTP, Telnet, FTP, RIP, UDP, and so on. Its name comes from the two most important protocols-------TCP and IP. They are in the second and third tiers of the TCP/IP model.Second, OSI Reference Model and TCP/IP Reference ModelThe IP world is the process of the communication entity, and the communication entity is to be layered. The benefits of layering are:1, each layer is independent.2, good flexibility.3, the struct

. The header that a group must carry (containing necessary control information) also causes certain overhead. Comparison of Three Types of forwarding Network layered protocol model Name the PDU based on the protocol of the TCP/IP protocol cluster: Application Layer data generally refers to the PDU used by the application layer. Transport Layer Data Segment transport layer

implement it next time, you only need to know what services the next layer provides for me and what services I must provide for the previous layer. -- When the implementation of a layer needs to change due to technical changes, other layers are not affected. 1) when the ISO/OSI reference model data is sent, It is uploaded from the seventh layer to the first layer, and the opposite is received. The upper layer is called the application layer, which is