Hou Ziqiang: broadband IP MAN and access network technology advances

Hou Ziqiang: Institute of Acoustics, Chinese Academy of Engineering Center researcher DSP, China Network Communications Inc., Chief Scientific Adviser

A broadband IP MAN MAN traditional telecommunications system using SDH TDM provide dedicated services, systems and high cost, limited bandwidth, laid long period, far from meeting the needs of next-generation broadband MAN. The requirements of the new generation of broadband MAN can be summarized into the following points: (1) scalability, bandwidth can be extended to a few hundreds of Gb / s, and even Tb / s or more; (2) can have as many as several 100 nodes; (3) low cost, including low capital cost and operating costs; (4) to support next-generation IP-based business, can support a variety of physical interfaces, QoS, SLA, monitoring and billing system; (5) support for traditional voice and data services; (6) powerful and easy to use network management system; (7) robust, with a 99.999% working time, hardware redundancy, self-healing fiber ring fault protection capability.

  Structure in light-line metro Gigabit Ethernet is becoming the mainstream. The current trend is to Ethernet and wavelength division multiplexing (WDM) technologies in the cable line directly into a broadband IP MAN architecture. Now with Gigabit Ethernet will soon become a bit Gigabit Ethernet.

DWDM technology in the WAN application of great success, becoming the mainstream, but we can not simply be implanted in the metropolitan area. Interval between adjacent wavelength DWDM systems only 0.8nm (100GHz) or lower, and the frequency accuracy of the laser, monochrome and filter demanding very expensive. However, long-distance wide area network, the use of multiple amplifiers, DWDM system in optical fiber multiple wavelength channels and amplifier sharing, and therefore can still be a significant reduction in WAN costs. The MAN shorter distance (typically 100 km or less), do not use amplifiers to increase the cost of a single fiber is not high, so simple to use and wide area networks like DWDM equipment is not necessarily cost-effective. The solution is to use sparse wavelength division multiplexing (CWDM) technology. It uses 1200 ~ 1700nm wide window, the requirements of the lasers and filters can be greatly reduced, and dramatically reduce costs. Another method is to WDM optical transmission equipment and routing switches combine routing switch port directly drive optical transmission equipment. The simplest case, a fiber optic only way data transmission, to run directly on the bare optical fiber Gigabit Ethernet. If you need multiple streams of data can use wavelength division multiplexing system, gradually increase the wavelength channel as needed.

In the routing switches to connect nodes each wavelength channel, which is responsible for routing the exchange of erection ceded / insert effect. This add / drop effect not only on the wavelength of the task can be, even on the data flow packets.

With Gigabit Ethernet in optical-line structure to meet the new generation of broadband IP MAN MAN’s requirements and take into account the traditional practice of business, need to address the following issues: (1) According to the SLA, QoS, Bandwidth allocation ; (2) to provide traditional TDM-based telecommunications services, such as leased line, etc.; (3) for access network concentrator, the LAN inside the building to solve the same mutual segregation between different users, each user multi-service flows, respectively management (to improve different QoS) and billing issues, and to provide video broadcast multicast, asymmetric approach to service; (4) fiber-optic ring is cut protection and fault recovery.

Current L2/L3 integrated Gigabit Ethernet Routing Switch backplane capacity has reached hundreds of Gb / s, packets per second by volume of more than 100 million; the third layer can be wire-speed IP / IPX routing and the second non-blocking switching; support redundant ports, spanning tree, multi-choice routing and redundant router protocol to increase system reliability; can provide hundreds of 1000Base-X ports; to provide bandwidth management, priority and policy-based QoS; can easily through HTTP, SNMP, RMON, CLI for flexible local and remote management. Some devices can support thousands of IEEE802.1Q VLANs, and is compatible with the link aggregation IEEE802.1ad technology to combine multiple Gigabit Ethernet ports into a trunk, the load balancing between multiple ports. For the Ethernet MAN, the most difficult is how to connect without providing end-to-IP Internet connection, TDM circuit emulation. Some companies (such as Extreme) products are beginning to provide IPTDM business. Core network of VMAN and VLAN with access networks, transmission delay can be fixed voice and video, as the public telephone network to provide the equivalent of IPTDM E1 channels, but this is not true TDM channel. RAD’s TDM overIP, in a transparent T1/E1 IP line circuit, the method is: the data package insert synchronous bit stream, plus IP header into the IP network transmission, data packets transmitted through the IP network to the finishing point synchronized clock in the end of reconstruction, excluding header, to provide synchronous bit stream. Of course, the transmission of IP network data stream to give QoS guarantees, the user interface, standards-based leased line (T1, E1); 10/100Base-T Ethernet network interface is a low cost; you can configure QoS options: VLAN for the first second floor of priority (802.1D), ToS priority for the IP layer to determine, UDP port for the fourth level priority packet delay variation compensation. This system has the external / adaptive clock regeneration, processing delay is very short (less than 1ms), scalable, backup and redundancy management and diagnostics. This device can be used to provide TDME1 IP Internet line, than SDH and ATM networks to provide the E1 cheaper. Metro Ethernet SDH equipment not in use, when the fiber loop is cut off, like how to like SDH self-healing within the 50ms restoration is needed to solve the problem. Currently the first layer in the network to the third layer are solutions. DWDM system in optical light path switching can be completed within the fault recovery in 50ms. The second layer of resilient packet ring (ResilientPacketRing, RPR) can be carried out as quickly as SDH fault recovery, and can transfer data using loop back up some. The latest routing switch can be completed in the third layer ring network or mesh network fails, fast fault recovery. One way is to calculate well in advance of possible failure of the recovery path routing table, once found fault monitor rapid conversion to the backup path; Another approach is to use MPLS to achieve fault recovery.

New generation of Gigabit Routing Switch hot-swappable modules and components, system software, and a double-double system configuration, to achieve carrier-grade reliability; a flexible management capabilities, it is convenient to local or remote, by browsing Used SNMP, RMON command for flexible management.

1. RPR Multi-Service