Several parts of the transport layer Alcap, SSCOP, Mtp3-b, SCCP, Saal, SCCF, STC, IP, UDP, GTPU

Several parts of the transport layer Alcap, SSCOP, Mtp3-b, SCCP, Saal, SCCF, STC, IP, UDP, GTPU

Physical layer: The physical layer mainly provides the transmission channel of ATM cell, which will form a continuous bit stream after the cell from the upper ATM layer plus its transmission overhead. At the same time, after receiving the continuous bit stream from the physical medium, the effective cell is removed and passed to the ATM layer.

ATM Layer: ATM (asynchronous Transfer mode, asynchronous transfer mode) layer is on the physical layer, using the services provided by the physical layer to communicate with the peer layer in units of cells. The ATM layer has nothing to do with the type of physical medium, the concrete implementation of the physical layer, or the type of service it transmits, it only identifies and processes the letterhead. That is, the ATM layer is responsible for the upper layer from the 48 bytes of cell payload plus 5 bytes of letterhead, or the physical layer from the cell to remove the letterhead to the upper layer.

The AAL layer: the AAL (ATM adaption LAYER,ATM adaptation layer) is located above the ATM layer, called the ATM adaptation layer, which is business-related and is handled differently for different businesses. The AAL layer divides the flow of information (length, rate) from the upper layers into 48-byte long ATM business Data units (SDU), while the ATM SDU is assembled and restored to the upper layer.

The Aal2:aal2 is targeted at low-speed, variable-rate services with timing requirements, such as compressed speech. This business produces smaller packets, and one packet is not enough to fill a cell. If you want to accumulate a user's multiple packets to fill a cell, it may result in a relatively large delay. The AAL2 protocol is to reuse multiple users on an ATM channel, which is to populate the cells with packets from multiple users, and each packet is preceded by a header to indicate which user it belongs to. AAL5:AAL5 is an AAL protocol based on the AAL3/4 protocol that is designed to improve efficiency and specifically target the class C connection-oriented business.

Saal: In order to be able to transmit signaling information in an ATM network, it is necessary to make a signaling adaptation function, to convert signaling information in various message forms into a form transmitted in an ATM network, and to establish an AAL connection for signaling. The completion of this function is the signaling ATM adaptation layer Saal.

The SSCOP:SCCOP provides SSCOP users (that is, SSCF entities) with transmission information up to 64k bytes of reliability transmission. The function of SSCF:SSCF is the SSCOP and upper-level user's adaptation layer, in which the upper user mainly refers to NBAP, Mtp3-b and STC (Signal Transport Convert, signaling transfer conversion). Because the Saal upper layer is different, such as Mtp3-b is located in the Nni,nni link quality is generally high, also need to Saal support link quality verification and with Mtp3-b for link switching function, and NBAP in uni, the quality of the link is generally poor, the delay is large. So SSCF is divided into Sscf-nni and sscf-uni to fit different upper-level users.

The Alcap:alcap (Access Link Control application part, Access Link Controls application protocol), also known as the Q.aal2 protocol, adheres to the ITU-T q.2630.1 specification and is in iub/iur/ Iu-cs the control surface of the transmission network layer, the signaling bearer type is Saal uni and mtp3-b. The Alcap interior consists of two layers, Q.aal2 protocol processing layer and two STC adaptation layer. The Q.AAL2 protocol processing layer completes all protocol functions, and the STC completes the primitives to mask the underlying differences (Saal, mtp3-b). The basic function of ALCAP is to establish and release a AAL2 connection between two signaling points. At the same time, it makes necessary maintenance and management for the channel, access and other resources of the signaling system. These AAL2 connections controlled by the Alcap are used as transmission vectors for the wireless network layer control surface and the wireless network layer user plane.

RNSAP: Wireless network subsystem application section IUR data stream (s): IUR interface Data stream SCCP: Signaling Connection Control Section Sccf-nni: Specific business coordination Function-Network Node interface STC (Signal Transport Convert, Signaling transfer conversion) Mt3p-b:mtp3-b is the protocol specification specified on the basis of the original MTP3 for ATM characteristics. As signaling transmission layer, mtp3-b not only responsible for the bearer of signaling messages, but also responsible for signaling network, signaling link management. Mtp3-b uses the services provided by Saal for message exchange.

The purpose of the SCCP:SCCP (signaling Connection control part, signaling Connection Controls section) is to enhance the function of the message passing part (MTP), which is equivalent to the third layer of the OSI, which realizes the packet switching function of the virtual circuit and datagram. Since the MTP's addressing function is limited to passing messages to the node, it can only provide a non-connected messaging capability, while SCCP uses DPC (Destination point code, destination signaling dot code) and SSN (Subsystem number, subsystem number) to provide an addressing capability to identify each SCCP user in a node. Stc:alcap's adaptation layer, including Saal STC and Mtp3-b STC.

Iu-cs interface protocol stack structure 1-5 shows RANAP: Wireless access Network Application protocol Iu up Protocol Layer:iu Interface User Surface Protocol layer IU-PS Interface protocol stack structure 1-6 shown.

The IP:IP protocol (Internet Protocol) provides a global, unified addressing approach that masks differences in physical network addresses and makes routing lookups possible. At the same time, IP protocol provides a global unified message format, shielding the network link layer differences, making network interconnection possible. The IP datagram protocol is very simple and does not guarantee the reliability of the transmission. IP protocol to achieve point-to-points transmission, the IP layer peer-to communication between peers not through the intermediary machine, the equivalent of the machine is located in the same physical network, the peer machine has a direct physical connection between the IP layer to point to the key of the communication is to find the path, according to the IP address how to determine the next point of communication. UDP:UDP (user Datagram Protocol) is a Subscriber datagram protocol that provides no connection service, which adds port addresses on IP basis to differentiate between different applications on the same host

The function of the gtp-u:gtp-u (GPRS tunnel Protocol user PLANE,GPRS Channel protocol-client side) is to iu-ps the transmission of user-side data and path management. Since 3G supports the transmission of various types of packet data, and because the enhancement of functions may support more kinds of packet data in the future, Gtp-u uses a common tunneling encapsulation method on GTP basis to transparently encapsulate various types of packet data in order to support various types of packet data.

Several parts of the transport layer Alcap, SSCOP, Mtp3-b, SCCP, Saal, SCCF, STC, IP, UDP, GTPU