Multi-service transport platform (MSTP) refers to the SDH platform, which realizes the access, processing and transmission of TDM services, ATM services, Ethernet and other services, and provides a unified network management multi-service transport node.
- EOS technology
Based on SDH/SONET Ethernet data access technology (ethernet over SDH/SONET, EOS), MSTP provides a friendly platform for dispatching data network and other data service access. Ethernet services are processed through access, encapsulation, mapping, virtual contatenation (VCAT), link capacity adjustment scheme (LCAS) and other steps to realize Ethernet data packets on SDH/SONET networks It is transmitted in the frame format of the transmission device.
(1) Business access. The MSTP Ethernet interface board is divided into one-layer transparent transmission board, two-layer switch board, and two-layer half-Ethernet board with partial routing function. It is physically divided into electrical ports and optical ports. The rate is FE/GE (100M/100M). ) Optional.
The transparent transmission service directly encapsulates the data packet into the SDH VC. The two-layer service uses the IEEE802.1D transparent bridge algorithm to realize the communication between different Ethernet ports on the Ethernet interface side and different VCs on the system side according to the MAC address of the data packet. Packet switching can also switch data packets according to the VLAN TAG of IEEE 802.1Q, providing multi-user isolation and VLAN division on the service layer; at the same time, the spanning tree protocol STP can be used to achieve layer 2 protection for Ethernet services, and some also provide IEEE-based Priority forwarding of 802.1p. RPR (resilient packet ring, Resilient Packet Ring) adopts a dual ring (inner ring and outer ring) structure, using SDH VC as a virtual ring, and there are two paths between each pair of nodes, ensuring high availability and realizing all loops Node bandwidth is dynamically allocated and shared.
(2) Data packaging. There are GFP, HDLC, PPP, ML-PPP, LAPS and other methods for encapsulating Ethernet services into SDH frames, among which GFP (generic framing procedure) is widely used.
(3) Mapping. Adopt adjacent concatenation/virtual concatenation of VC channels to ensure the integrity of the data frame in the transmission process; VCAT technology can make the GFP frame be divided into several non-concatenated VCs for independent transmission, and then arrive at the receiving end. Combine the data to restore the original GFP frame, similar to the VC trunk channel, called VCTRUNK. For example, a VCTRUNK is bound to 3 VC3s, which actually provides a virtual channel with a bandwidth of 3 VC3 capacity. Different VCs The composed VCTRUNK provides a virtual channel, users can use this channel to transparently transmit data, without having to care about the specific path that the fragmented data passes. The reserved field in the virtual concatenation multi-frame can realize automatic recovery when a certain VC channel fails, and can ensure that the service is not damaged when adding and deleting services dynamically.
The more commonly used bundling rate corresponds to the rate of 10M/100M/1000M. 5 VC12 (2M) are bundled into 10Mbit/s, 3 VC3 (34M) are bundled into 100Mbit/s, and 7 VC4 (155M) are bundled into 1000Mbit/s. .
LCAS can automatically adjust the size of the virtual concatenation group without interrupting services, which can overcome the shortcomings of SDH fixed bandwidth and achieve dynamic bandwidth.
(4) Cross connection of SDH. The speed and direction crossing between VCs is completed.
- Interface with dispatching automation data equipment
Obviously, MSTP can provide point-to-point services for the data network for one-layer Ethernet service boards; it can provide point-to-multipoint services for two-layer Ethernet service boards, and also has some aggregation functions, especially for LAN and VLAN services. Access mode with TAG tag, TRUNKING mode with TAG tag, mixed mode with or without TAG tag, and QINQ mode with TAG tag nesting of VLAN. For the VPN service of the power data network, the two and a half Ethernet service boards provided by MSTP can be configured with MPLS functions to realize MPLS VPN end-to-end services.
