On some key technologies involved in the construction of metropolitan area network

1) Routing problem network The third layer of equipment has the most important role of two: The calculation of routing table and forwarding packet; The table entries in the routing table indicate the network that the device can achieve, so the routing problem is a key problem in order to realize the data exchange on the network. When considering the route of network, it is necessary to take into account the accessibility and adaptability of the routing, and fully consider the security, avoid the network circuit and other factors. 2 Multicast problem data network support for multicast is an important symbol to measure the capability of multimedia service in this network. Multicast groupings are identified by a unique multicast address, the group number is selected by the host that sent the packet, not the network, and any host can send multicast information in a multicast group, regardless of whether it is a member of a multicast group, but only members of the multicast group can receive multicast information. The membership in a multicast group is dynamic, and the host can join or leave at any time, and a host can be a member of several groups at the same time. In the network we build, the conversation between the multicast host and the gateway is controlled by IGMP/CGMP, and the transmission of multicast routing messages between gateways to gateways is realized through PIM (Kyoto Independent Multicast). 3 End user Access problem if the user is simply connected to the previous LAN mode, it will lead to obvious insecurity (because of the situation where multiple users coexist in a broadcast domain), then a new end user access method is needed. 4 Network management traditional data network management is based on in-band (in Band) management, in this case, the management of the data stream and the common data stream share the transmission channel, in addition to the IP protocol itself, the openness of the factors will seriously affect the security of the network, but the management of all changes to the Out-of-band and there is no very mature method. Joint ventures recommended a combination of both in-band and Out-of-band management. 5 network security to establish such a large network, security is very important, we mentioned earlier in the network management, user access, routing and other issues are related to the security of the network, the company in the network using a variety of security technology to achieve a full network of multi-level security (multi-level Security). 6 Virtual Private Network virtual private network (VPN) is a network service provider to users of the network resources, from the perspective of use, observation, management, such as the VPN is like a user's private network. A VPN domain provides users in a domain with a business similar to a closed user group. VPN Business is one of the basic services that our broadband IP hosting network should be able to provide. For IP networks, we hope that the VPN can provide users with independent management, billing, address planning and other work, its efficiency, security, operability and reasonable charges should be able to be more satisfactorily resolved. Second, the network platform authentication, billing and application withWith the construction of broadband IP metropolitan area Network, service providers are confronted with the opportunity of increasing business growth opportunities without counting. Users also require a variety of new services, such as broadband access, VPN services, VOIP, web hosting and so on, in order to realize the potential value of the new network business, to obtain economic benefits and competitive advantage from the newly-serviced projects, it is necessary to measure, analyze and provide flexible billing for the enhanced services. To make flexible and reasonable billing, it is very important to collect all kinds of data on the Internet, which is more complicated than the collection of call records in the traditional PSTN network. First, the nature of IP packets requires a lot of usage records, which can overload the infrastructure. Secondly, the distributed characteristics of IP services require data collection and processing from multiple resources. For a large number of radius-connected users (for example, via ADSL access), users can be authenticated and billed in a radius manner. In IP metropolitan area network billing, for users with fixed IP address access through a dedicated line, because routers and some three-tier switches support NetFlow functions (such as CISCO7206, Catalyst 6509, etc.), the information of the flow is counted, and the output contained in a certain format is included for billing , traffic analysis of the UDP packet, my company billing software collection of these and billing-related data, and then the data sorting, summary, accounting processing/collection of arrears, such as a series of processing. For networks that do not support three-tier switching and NetFlow functions, such as those that use non-Cisco devices or that do not support NetFlow features, these enterprises want to be billed separately for each employee or department while they want to see the overall usage and billing information from the service provider. You can use the SNMP method to obtain billing-related data from the MIB of a Cisco router or switch.