Author: Zhang XiuPing
In recent years, soft swapper has got the extensive attention of the industry, organize ITU-T, ETSl, 3GPP and IETF to all carry on research and canonial formulation to soft swapper in different categories in international four major standards. China International Organization for Standardization make work even, all in all, the standardized work is in forefront of the world. Several big operators in China add into networking of softswitching too, views from the point of introducing into the angle, only have two ways, one is introduced from long distance, optimize and shunt the existing VOIP business, if China Mobile and China defend openly. One kind is introduced from here, offer all kinds of new business fast, seize the market, mainly display in the traditional fixed operator, softswitching happens to offer such technological means.
It disposes softswitching to be mature recently at whole the whole network, feasible either. Because it is a technical matter that this is not simple, it involves respects such as current operation system, management system,etc. yet. This text the intersection of network connection and situation in softswitching carry on discussion, analyze the intersection of network and organization, IP of softswitching bear the weight of the intersection of network and organization, the intersection of safety and the intersection of design,etc. and respect content emphatically mainly, and combine the network architecture of softswitching of China Railcom of Shaanxi to explain.
Network organization of a softswitching
The softswitching network connection includes two respects: Softswitching is asked route design and road network and designed. It mainly means the signalling between softswitching is organized, generally adopt SIP-I agreement that the route is designed; It mainly refers to the intercommunication of speech path of different media gateways that road network is designed.
(1)A route is designed in softswitching
Define an area where SoftSwitch has jurisdiction over calls a control domain. In the route design, need to carry on the division of the control domain, no matter which kind of control domain is taken divides the way in a plurality of softswitching, involve addressing in gateway device, route organize the issue. The route can be divided into 3 kinds while organizing the way: The whole level ways, hierarchical ways and positioning the server way. When the whole level way is used for the initial scale of softswitching being minor. The hierarchical way follows PSTN mature multiple route system, make each of route data of SoftSwitch relatively simple, and make the architectural comparison of the softswitching network connection clear. Position two kinds of signallings on the mode change of the server and organize the way in which hop-by-hop transmits, utilize reachability of IP directly, SoftSwitch positioning the Opposite terminal directly, the signalling is simple and clear in switching.
Because the interoperability among the current apparatus of softswitching producers is discrepancy at present. Above-mentioned three route organize way feasible in the near future, position the intersection of server and way still in developing especially. In the real network connection, the whole network of trying not to be whole introduces softswitching, can introduce or introduce from the long distance from here, decide according to the original intention that the operator introduces softswitching specifically. The network connection of the signalling is to consider the way in which softswitching mix the network connection with traditional TDM, wait until every the intersection of producer and problem of interconnection can introduce into softswitching grade and the whole route of level organize the way progressively solve. The signalling route of Xi'an China Railcom is designed like this: Because Shaanxi iron; Open not to build LSTP, the signalling has been received to SG by the end office, visits SS through SIG-TRAN agreement, SS inquires about the domain SHLR: If is the ordinary call, SS controls TG to continue the speech path through H.248 agreement, the signalling is from local SG to every end office; If is the intellectual service call, SS visits the softswitching operation platform (China is an intelligent network SCP) through SIP agreement Touch off the intellectual business.
(2)Network design of speech path
Because of adopting the technology that IP transmits fast, it is the complanation that the speech path of softswitching is organized, has no tandem of speech path, should consider QoS and safety in the network design of speech path mainly. Bear the weight of the network to realize in IP by technology of NPLS VPN at present. Because TG (relay the gateway) , AG (insert the gateway) , IAD (integrated access device, the IAD) And the intelligent terminal should realize the intercommunication of speech path, must adopt the all netted ways to join. MPLS logical link LSP (mark exchanges the route) All reticulate connections gave and bore the weight of the network to bring the challenge greatly, though industry can adopt VPN route reflector technology to solve, but large-scale MPLS VPN bears the weight of the network to implement in IP, and step the autonomous system (autonomous system, AS) Realization of MPLS VPN last case that be supported in practice. In the near future, propose the speech path to organize or adopt and mix the network connection way with TDM, keep softswitching land confined within here or long distance. While introducing here, because the ground mat of staying will dispose lAD and intelligent terminal on a large scale, the function that the ground mat supports MPLS VPN is unrealistic to demand to stay, propose clicking or gathering together the joint to dispose the business and insert the control equipment (service access con in the metropolitan area network POP. trol, SAC) ,Restrain the traffic of lAD and intelligent terminal fast, filter and transmit the real-time traffic flow. To the above-mentioned analysis introductions, Shaanxi China Railcom adopts and designs as follows: As to local call, call out through the intersection of TG and switching between the the intersection of Xi'an and local network, user, Home Network of Xi'an, call out Extranet and Extranet, come go on switching to TG through former the intersection of pass and office; As to long trunk call: The Home Network of Xi'an calls out the long distance of strange land to continue to DCI long-distance office through TG switching; It is transferred from DCl office to TG apparatus that comes from the strange land, and then transfer to every end office.
2 IP bears the weight of the organization of the network
(1)IP bears the weight of the technical requirement for the network
The bearing the weight of the network of softswitching can be divided into 3 aspects: China's backbone network, metropolitan area network and ground mat of staying. Softswitching bears the weight of the is required the light load, security and has QoS to guaranteeing of the network to IP. The real-time interactive business born the weight of because of the softswitching network is different from the traditional Internet business, propose building China IP key Private Network alone, should support the function of MPLS VPN. The metropolitan area network is more complicated, according to the thinking of the operator at present, the metropolitan area network is unified, this needs metropolitan area network to possess the ability that the business shunts. The technology of the metropolitan area network can be divided into 4 kinds mainly:
Large-scale metropolitan area IP network
Require the core of metropolitan area, assemble layer and support P/ PE function, can construct MPLS VPN directly; The intra-area AG of the city, SAC apparatus direct connecting PE router, can insert PE apparatus through the transmission network or bilaminar VLAN periodic line too; Ss (SoftSwitch) , SG (the gateway of signalling) And TG apparatus, through realizing MPLS VPN intercommunication across AS land.
Small-scale IP network of metropolitan area
Require the city intra-area apparatus to support MPLS VPN in principle. For not supporting, the edge floor can support the function of distributed PE at least.
Purely bilaminar ether metropolitan area network
The bilaminar switchboard apparatus that AG, SAC insert must support the segregation of VLAN, as to different users, traffic flow, isolate by dividing different VLAN; Finish different VLAN to VRF (VPN route rotates and issues) of different VPN through intercommunication of VLAN trunk way between metropolitan area network and backbone network PE apparatus Between related,access on is it different to realize to VPN.
MSTP metropolitan area network
AG, SAC insert the intersection of PE and apparatus of backbone network through MSTP directly, at the intersection of PE and apparatus until different MSTP insert port to be related to get different VPN VRF, realize the access of VPN.
Stay the intersection of ground mat and user adopting whom IAD inserting, require the intersection of IAD and apparatus its can support the intersection of softswitching and traffic flow and ordinary the intersection of Intemet and different marks to surf the Net traffic flow; The inner SAC facility request in the metropolitan area can discern its marks of the area IAD apparatus accused of, carry on the current divider of the business, introduce traffic flow and Internet traffic flow of softswitching into different networks.
