Mobile Telecom Unicom Large Customer Private Line End Access Solution

MSAP (Multi-Service Access Platform) is mainly targeted at the end access scenario of large customer leased line in transmission network. It integrates existing PDH, SDH, MSTP and Ethernet technologies to provide access, aggregation and transmission of TDM and Ethernet services on a unified platform, providing E1/V.35 leased line and leased line services as well as Ethernet leased line services, and providing a unified network management platform.

Background of MSAP

As we all know, in the early days, the end access of large customers' leased line was usually accomplished by PDH co-transfer, which solved the problem of availability and played a positive role in network application. However, with the development of business, the program gradually showed obvious deficiencies in network scalability, operation and maintenance efficiency.

At the end of 90, SDH/MSTP technology rapidly matured, China's metropolitan transmission network is basically realized using this technology, after years of development has been built into the world's most comprehensive coverage, one of the largest transmission network. Especially in the solution of private line for large customers, SDH/MSTP has become the best large customer solution recognized by the industry for its excellent security and high efficiency. As a natural extension of the technology, the use of SDH / MSTP equipment for large customer end access should be the ideal choice. However, due to the small but large number of access layer services, very price-sensitive, some of the lower business level of the private line business access layer network using a star-connected pure PDH optical terminal-based. This machine access method also brings a series of serious problems, for example: PDH optical terminal network single, optical port without a unified rate standard, the shortcomings are very obvious, to the entire network maintenance and sustainable development of the later stages of the network has brought a lot of inconvenience and obstacles. So operators began to look for a new technical means or solutions, not only has the advantages of low-cost, fast and efficient PDH, but also to overcome the shortcomings of the standard is not uniform, difficult to maintain, low quality of service.

MSAP came into being. Based on traditional SDH technology, MSAP adopts advanced GFP, VCAT and LCAS technologies, integrates Ethernet switching and SDH/" target="_blank" >ATM switching technologies, and realizes the integrated transmission of TDM, Ethernet and SDH/" target="_blank" >ATM services. Transmission. At the same time, MSAP has a lower system cost because it has a smaller capacity and more focused functions than MSTP equipment. Let's take a typical application scenario as an example to illustrate MSAP networking. MSAP equipment is configured in the user center room, which can flexibly access V35, E1, and Ethernet services of branch offices, which are encapsulated by GFP and converged into MSTP 155M ports. The user center room can be accessed through 155/622M fiber optic cable or FE/GE and other high-speed interfaces to the upper layer of the carrier's MSTP public network or IP metropolitan area network, and MSAP can be unified with the existing network SDH/MSTP network management, greatly simplifying the network structure, network scalability than the PDH has greatly improved.

Key Technologies of MSAP

MSAP has three key technologies to support its seamless connection with SDH/MSTP, and these three technologies also make MSAP more suitable as the end access solution for dedicated lines for large customers. These three technologies are GFP (Generic Framing Procedure), Virtual Cascade, and LCAS (Link Capacity Adjustment Scheme).

In order to improve the scalability of MSAP networks, GFP technology was developed, which is a standard developed by the International Telecommunication Union (ITU) G.7041/Y.1303, which provides a flexible and efficient mechanism for mapping different protocols into the transport network, defining a framing mechanism that supports the direct mapping of various communication types into SDH/MSTP frames. IP data services that were previously mapped with HDLC can now be mapped with GFP. The GFP standard allows for better optimization of the delivery of Ethernet and other data services over SDH/MSTP, and with MSAP support, services such as Ethernet can be freely delivered over existing SDH/MSTP transport networks via GFP encapsulation. With the support of this technology, services such as Ethernet can be freely transmitted in the existing SDH/MSTP transmission network through GFP encapsulation.

In order to improve the MSAP network carrying efficiency and flexibility, virtual cascade and LCAS (Link Capacity Adjustment Scheme) technology has been generated. The virtual cascade technology is relative to the traditional adjacent cascade technology of SDH/MSTP. From the early days of SDH/MSTP, adjacent cascade technology was one of its basic components to realize the need to accommodate high-speed data and high-bandwidth mapping. With the continuous enrichment of network applications, the application of adjacent cascade technology is subject to certain limitations, especially when carrying services represented by Ethernet, the container capacity does not match the service bandwidth and the mapping efficiency is low. For this reason, virtual cascade technology has gradually emerged and matured. Virtual cascade is formally defined in ITU standard G.707, which allows flexible binding of multiple non-adjacent SDH channels of different rates to create customized virtual cascade groups that can be any multiple of the base rate. This initiative has greatly enhanced the flexibility of SDH/MSTP networks and has become one of the fundamental bearer technologies for current transmission networks.

LCAS (Link Capacity Adjustment Scheme) technology is an important complement to the virtual cascade technology and is usually used in conjunction with it. This technique means that LCAS dynamically adjusts the link capacity through the synchronization information between the transmitter and the receiver during the capacity increase/decrease of a virtual cascade circuit, and ensures that the services in that virtual cascade circuit are not interrupted in the process. For example, if a single member of a virtual cascade circuit fails, the size of the circuit is temporarily reduced, but the virtual cascade circuit does not fail in its entirety, and the circuit size can be restored to its full bandwidth without affecting the underlying service once the single member defect is repaired. In addition to providing a resiliency mechanism for virtual cascades, LCAS provides service providers with the flexibility to adjust service bandwidth as needed. For example, if certain customers require additional bandwidth to transmit documents late at night (i.e., banking institutions), the operator can provide value-added services by supplying additional increased bandwidth during predefined hours. In summary, the combination of virtual cascading and LCAS can be extremely helpful in accessing applications at the end of existing large customer leased lines. In this case, virtual cascading is used to provision point-to-point connections on the network, while LCAS provides resilience to the virtual cascade connections and leaves room for further "tuning" of the allocated bandwidth.

MSAP Standards Development

The China Communications Standards Association (CCSA), a domestic standardization organization, has been making steady progress in the development of MSAP standards. The industry standard "Technical Requirements for Access Networks - Multi-service Access Node (MSAP)" was completed in 2009. The standard specifies the system network location and functional model of MSAP, functional requirements, SDH/PDH transmission Ethernet frame protocol, interface requirements, performance requirements, equipment timing and synchronization requirements, protection inversion, maintenance and management requirements and other requirements.

China's operators have developed MSAP specifications according to their own needs, and in 2008, China Unicom (formerly China Netcom) developed the "China Netcom MSAP Test Specification", which plays an important role in unifying MSAP technical standards and specifications.In March 2009, China Telecom also developed a similar "China Telecom MSAP Multi-Service Access Node Equipment Technical Specification (Provisional)", which further standardizes the relevant technical specifications. Provisional)", which further standardized the relevant MSAP applications.

Mainstream MSAP Vendors in the Industry

MSAP maximizes the use of the existing network resources of the operators to provide large customers with a wealth of private line access solutions, in terms of equipment space, wiring management, access, expansion and upgrading, reliability, construction and maintenance costs, network management, etc. are better than the traditional access methods, which are favored by the operators. Therefore, the MSAP market has become another piece of "cake" in recent years, the fierce competition among equipment manufacturers. At present, the industry's mainstream MSAP manufacturers are Huawei, Fiberhome Networks, Beijing Greenwell, Beijing Riskanda, Beijing is there, in addition, Beijing Huahuan, UT, Putian and more than 10 vendors have also launched MSAP products.

It is worth noting that Huawei has recently made frequent efforts in the MSAP market, first passing the China Telecom Group's MSAP test in 2010, and then successfully winning the China Telecom Group's MSAP procurement for the first time.At the beginning of 2011, Huawei's MSAP equipment successfully passed the China Unicom Group's 220 stringent tests, debuting with a 100% pass rate. Huawei's OSN3500II series of MSAP products extends its high-end OSN brand, which is actually a new multi-service access platform for the stable market of large customer access. This series of products continues the strong performance of OSN products, set SDH, PDH, fiber optic transceivers, protocol converters, optical cats, Ethernet switching, EOS and other functions in one, the business interface can provide modular V.35, E1, FE, GE data interfaces, 155M, 622M, 2.5G SDH optical interfaces, crossover, master, clock, power supply, and other important boards and cards can realize the 1+1 redundancy protection, can be seamlessly networked with MSTP networks to realize MSP, SNCP and other protection, and can be smoothly upgraded to STM-4/STM-16. In addition, the most noteworthy, the most powerful network management system, U2000, can unify the management of MSAP and all Huawei-produced network equipment, so that the operation and maintenance of carrier carrier networks has become extremely simple.

With the increasing demand of China Telecom, China Unicom and other carriers for end-of-line access for large customers, the steady progress of the development of the national standard for MSAP, and the active research and development of various equipment vendors, MSAP will continue to develop steadily and become the best solution for carriers to provide dedicated lines for large customers in the past few years, by virtue of its outstanding advantages in end-of-line access, low cost and strong scalability.