At present, it is universally agreed in the telecom industry that the next-generation network is based on multi-service IP bearer network. ATM network, as the former-generation packet switching network, will also gradually migrate to the IP network. Especially in Europe and North America where the telecom market is more mature and the technologies are deployed earlier, there is a great number of ATM equipment in the current networks. To protect the investment in the current network through smooth migration from ATM to IP, Huawei launches a complete ATM migration solution.

Huawei believes that such migration should be performed in a smooth and progressive manner: At the first phase, the multi-service IP bearer network is built to carry newly deployed services, while ATM network expansion should be stopped. At the second phase, when ATM network equipment is gradually aged out, the services and traffic previously carried on the ATM network should be gradually migrated to the IP network, until the ATM network is completely replaced by the IP network. Only such smooth migration path can provide maximum investment protection for carriers, reduce the migration risk, and ensure that service experience of end users is not affected.

After the new IP bearer network that can bear all the old ATM services is built, the second phase starts. There may be two scenarios: (1) Equipments that still use ATM interfaces or ATM subnets are interconnected through the IP bearer network; (2) The ATM network and the IP network access each other. For the first scenario, Huawei solution includes transparent transmission for all ATM interface types, cells, and frame formats, as well as built-in IWF feature. They can be flexibly selected for use in different cases, where the RAN equipment with ATM interface is carried by the IP network, ATM islands are interconnected through the IP bearer network, or traditional dedicated lines are transformed. For the second scenario, the Huawei solution offers termination of various ATM encapsulations, and flexible policy processing on the BRAS equipment. Huawei routers also support IP-to-ATM address resolution through manual configuration or InARP, suitable where a small volume of IP traffic traverses the ATM network.

For smooth migration of the QoS feature from ATM to IP network, the Huawei solution supports mutual mapping between the CLP/service types of ATM and the DSCP field of IP or EXP field of MPLS. The solution supports PVC-based forced traffic classification, providing DiffServ based on different priorities and service types. It also supports port- or PVC-based QoS. These functions make it possible for fine-grain classification of user traffic and further fine-grain operation of the IP network. In addition, the Huawei solution uses MPLS TE to provide bandwidth guarantee. Together with SIP protocol, the same effect of ATM CAC can be achived.

Remaining ATM OAM features should also be considered for the migration. The Huawei solution provides transparent transmission of various ATM OAM cells, as well as OAM cell genearation on PE equipment connecting to the ATM network, for sending alarms to the ATM equipment on the CE node. Thus, the ATM OAM functionality is retained in the IP network after the migration. The Huawei solution also provides interaction between ATM links and PWs. Therefore, failures on ATM links or PWs can be notified to each other. When a PW has a fault, it can notify the fault to the CEs on both sides through ATM links; if a CE on one side has a fault, it can notify the fault to the remote CE, ensuring carrier-class high-reliability of the network after migration.

The ATM migration solution from Huawei features smooth migration path that offers maximum investment protection and minimum service impact, Currently, this solution has found successful applications with operators such as Vodafone in Romania, QSC Germany, and Marco Telecom, and it will surely help more operators in migrating to the next-generation IP network.