subject: The next generation of high-capacity metropolitan area network architecture and key technologies - networks, Ethernet, communication - communication [print this page] The next generation of high-capacity metropolitan area network architecture and key technologies - networks, Ethernet, communication - communication
1, Introduction Now widely used around the world of MAN technology architecture mainly SDH, Ethernet, which uses wavelength division multiplexing (WDM) technology expansion to 1Tb / s when the cost in addition to the above, but also have their own shortcomings when applied to metropolitan environment: SDH is a transmission system for time division circuit, but in age groups, data transmission business will become less efficient; Ethernet naturally suited for packet data transmission, but it difficult to apply to ring topology, there is no ability to take full advantage of ring, and quality of service (QoS), reliability and scalability can not meet the requirements of telecom.
Newly IEEE802.17 standardization of resilient packet ring (ResilientPacketRing, RPR) technology is effective to support fiber optic ring topology and failure and link failure when the fast recovery time; the same time, to provide as efficient as Ethernet, simple, low-cost data service transmission. RPR can also use the WDM expansion (RPRoverWDM), is widely favored MAN technology. However, the design of RPR did not take into account the use of wavelength routing, so when the capacity reaches 1Tb / s, the number will increase to tens of wavelengths above, each node needs a large number of transmitter and receiver, the cost is high. And packet ADM can be designed over the wavelength received dozens of two-way data packet, and transmission line to be designed to dozens of two-way data packet sent over the structure of the wavelength, this design is undoubtedly the most expensive. With high-speed tunable devices
maturity, combined with wavelength routing, a new high-capacity metropolitan area network architecture has become very competitive solution.
2, a new framework for the next generation of high-capacity metropolitan area network
This new high-capacity metropolitan area network architecture shown in Figure 1: is a 2-fiber bidirectional ring topology, nodes using fast tunable packet transmitter to plug into the ring group, the group using the destination node to receive wavelength transmission. Each node only receives from the ring, the only wavelength of the data packet. As business is passing the middle layer of an optical node through, and do not need to be intermediate nodes, so I can greatly reduce the end to end delay, and more easily extended to higher speeds up.
Consider the example shows, the node I want to transfer the two groups, one to the node 0 and 1 to Node 1. Suppose node O in the wavelength 0 to receive packet, the node receives a packet on the wavelength 1. Transmission node I transferred it to the transmitter wavelength 0, and inserted into the packet destination is node 0. Then transferred it to the transmitter wavelength 1 and inserted into the destination node 1 packet. To the node O of the group of wavelengths and the wavelength of other nodes can receive consistent, so it is in the ring of light is transmitted directly to node O, where the last was received and processed. Packet to node 1 is the same process.
In RPRoverWDM system, the two groups will be received via the node, converted to electrical signals, transmitted packet ADM, and then between the source and purpose of each node forwarding. This RPRoverWDM nodes because they have to receive, process and forward all through the group, and require very much equipment. In the new framework in the node only need to deal with the packet sent to it, can greatly reduce the device to simplify the structure and reduce costs.
3, the key technology of new architecture
New architecture requires new protocols, such as media access control, fair agreement, the survival of agreements, which are the key to this new technology architecture.
3.1MAC agreement
Due to wavelength routing in the packet ADM to deal with the current ADM of any commercial network handling is completely different from the MAC protocol must be the development of a new beginning for the data link layer protocol. The main function of the MAC protocol is to prevent the transmitter into data packets in the nodes of conflict.
