Summary of the Practical Application Experience of the softswitch network routing system

There are many areas worth learning about the softswitch network. Here we mainly introduce the key Routing Technology in the softswitch network. When a traditional telephone exchange network is establishing a call, first, identify the signaling point encoding of the next exchange board based on the E.164 number called, and then route the call through the No. 7 signaling network based on the signaling point encoding, the essence of all call routes is to determine the signaling point encoding according to E.164, and then use the signaling point encoding for call routing.

Unlike traditional PSTN (PublicSwitchTelephoneNetwork) networks, the next-generation network call routing based on the softswitch network is to determine the next hop Softswitch Network Based on the address of the called USER or directly locate the called terminal. The address of the called user can be in the form of E.164 number, URL (uniform Resource Locator, uniform Resource Locator) or IP address.

The convergence of networks and the diversity of addressing methods make the original PSTN network and IP network routing methods no longer meet the communication needs. In the next generation network routing technology, the problem of number translation must be taken into account. Therefore, it is necessary to study the next generation network routing technology. This article focuses on the key routing technologies involved in large-scale next-generation Softswitch networks. These technologies are of positive significance for the development of next-generation networks based on SoftSwitch.

The control layer in the Next Generation Network is closely related to the business and needs to deal with various systems, such as routers, application servers, and database subsystems. This is part of the true embodiment of network intelligence. One of the most important problems to be solved at the control level of the Next Generation Network is the routing problem. So what is the Routing Problem of the Next Generation Network?

(1) User positioning and network addressing issues;

(2) There is a routing connection problem between different NGN (NextGenerationNetwork, Next Generation Network) networks;

(3) questions about the mobile application of NGN users.

Next-generation network routing Solution

To address the above problems, the industry has proposed a variety of solutions for next-generation network routing.

1. Hierarchical Softswitch Routing System

For large NGN networks, we use the idea of PSTN layering to divide the softswitch network into different layers for multi-level routing. However, the user-side bearer is still the end-to-end packet bearer. NGN network services are divided into two types: Intra-domain services and Inter-Domain services. The intra-domain service refers to the softswitch service in a certain area of NGN. The intra-domain Softswitch service only needs to know the routing information in the region. For routing information not in the local region, you only need to forward the call request to the Inter-Domain interconnection Softswitch that is connected to the intra-domain service SoftSwitch.

The service Softswitch in the region focuses on providing a wide range of services for users in the region. The Inter-Domain service Softswitch Network is responsible for routing between different domains of NGN. In the case of a large number of softswitch routes for Inter-Domain interconnection, you should consider dividing the Softswitch networks for Inter-Domain interconnection into multi-level structures, but the softswitch of all intra-level services is still a plane structure. This hierarchical routing Static Routing Method follows the multi-level Routing System of the PSTN network. The advantage is that the routing data of each Softswitch is relatively simple, and the network structure of the entire network is very clear.

2. Locating Server Routing System

The requirements for NGN determine that any switching device in the network can directly locate the peer device, without the need to send call signals by jump, you can set the shared location server in a centralized manner to meet such requirements. When a certain area of the softswitch network expands to a certain number, the locating server can provide routing services for the softswitch in this area. Mutual routing information can be maintained between Softswitch in the domain to ensure rapid call establishment. At this time, each Softswitch only contacts the corresponding locating server, and the locating server locates the destination Softswitch Network.

In this case, the softswitch stores the complete routing information of the user in the control range and the routing information between the softswitch in the same domain. At the same time, you can also consider establishing a local ing library for some common addresses in the softswitch or locating server to speed up the call connection. Locate the number of servers based on the network capacity.

The locating server is not a standard network entity defined in the next generation network framework, but a functional entity proposed in the Next Generation Network to solve large-scale network routing problems, therefore, the functions and features of server locating have not been recognized by the industry. Different equipment manufacturers have different practices.

The main function of locating a server is to exchange information between locating servers through protocols, and accept Routing Query requests through protocols. The locating server supports routing information such as E.164, IP address, and URL. It supports multi-layer structure similar to PSTN and can be divided into different domains and layers. All levels of locating servers have the collection and query functions. They provide security services and can implement monitoring and other special services according to users' special needs.

From the way of obtaining route information, the locating server includes Static Routing and dynamic routing. Static Routing refers to the static configuration of routing information between servers and between the softswitch server and the locating server. Because both the softswitch server and the locating server have static IP addresses, you can save the correspondence between user numbers and IP addresses in the locating server and the softswitch server. To overcome the disadvantages of poor flexibility in Static Routing, different vendors adopt TRIP (TelephonyRoutingOverIP, IP telephone routing Protocol), LDAP (Lightweight Directory Access Protocol, Lightweight Directory Access Protocol) DIAMERER, RAS (Registration Admission Status, permitted Registration Status), H.323 Annex G, and other protocols to locate the dynamic routing between the server and the locating server, and between the locating server and the softswitch server. It is precisely because different manufacturers adopt different protocols to achieve dynamic routing that communication problems exist.

3. Dynamic Routing System Based on DNS (DomainNameSystem, Domain Name System)

In the NGN system, the E.164 number, URI (UniformResourceIdentifier, unified resource identifier) address, and IP address end users both exist. A user has multiple address modes, such as the Session Initiation Protocol (SIP). A terminal must have an E.164 number when communicating with a POTS user. The URI address can be used directly for communication between SIP terminals. When the URI address in the NGN network is widely used, the dynamic routing of the NGN network can be achieved through a mature DNS system. In addition to the traditional Domain Name Translation DNS, which is widely used on the IP network, the NGN network also introduces a new type of DNS, this new type of DNS uses the ENUM (Telephone (E.164) Number Mapping, Telephone Number ing) Protocol to map E.164 numbers to URI addresses, called enum dns.

The ENUMDNS system adopts a hierarchical tree structure, which is exactly the same as the current DNS system. When the NGN network grows to a certain scale, it is necessary to consider carriers and international interconnectivity like the InternetDNS system. At this time, we must plan ENUMDNS globally.

The first hierarchical softswitch network routing method has obvious advantages. Its implementation technology is mature, its network layers are clear, its structure is simple, and it is easy to maintain and expand, at the same time, the softswitch network can provide the gateway function for the external network, so there are no too many interconnection points, which ensures the security of the internal structure and information of the network. However, the disadvantages of this routing system are also very obvious: signaling requires jump-by-jump transmission, and each Softswitch Network passing through in the middle needs to process the call signaling, resulting in a large call latency. The second and third solutions involve two emerging routing technologies, which are described below.