MSTP Technology and ZTE´s Solutions

MSTP with L2 switching function greatly improves multi-user/multi-service bandwidth sharing and isolation. Based on the relevant standards in the industry, the EOS technique used in ZTE´s MSTP system expands and improves many functions.
    With an embedded RPR, ZTE´s MSTP may process the QoS requirements of Ethernet services, allow scalability, and support such functions as multipoint-to-multipoint connection, user isolation, bandwidth sharing, Ethernet service QoS, SLA enhancement, congestion control, fair access and ring protection on service layer.

    ZTE always contributes to the study of MSTP standards. Up to now, it has submitted to ITU-T several proposals on MSTP. Moreover, ZTE has drafted number of national standards on MSTP for China.

    In China, ZTE´s MSTP equipment participated in numerous tests and certifications sponsored by authority institutes and operators, and passed all of them with good performance.

More information at:
http://www.zte.com.cn/English/03product/more1.jsp

1 Multi-Service Transport  Platform (MSTP) Technology
The Synchronous Digital Hierarchy (SDH) technology appeared in1980s. Two decades of development has proved its unique advantage and market situation. Meanwhile, due to data service, SDH transport network has to transmit multiple services. SDH technology accordingly needs improvement and innovation. The representative of new generation SDH transport network is the MSTP called in China or Multi-Service Provisioning Platform (MSPP) called in other nations. Based on SDH hierarchy, MSTP may access, process and transmit Time Division Multiplexing (TDM), Asynchronous Transfer Mode (ATM) and Ethernet services in one platform, and provide uniform network management. It fully satisfies the present requirements of transmission network. Other transmission modes also arose in the evolution from traditional SDH to MSTP, but the MSTP technology is very advantageous in performance and the costs of construction and maintenance. Therefore, it is still the mainstream technology applied in the transmission network.

    Simply speaking, the MSTP technology resolves number of problems in traditional SDH technology. It has the following characteristics compared with traditional SDH:

• Excellent capability of multi-service access and multi-protocol processing
• Quality of Service (QoS) guarantee
• Fast network configuration ability
• A large quantity of multi-line interfaces
• High cross connection capacity
• Ability of network capacity expansion with low cost
• Simple and easy improvement of topological structure
  

    New demands for transmission network push constant advancement of MSTP technology. For example, in order to support Ethernet, MSTP goes through three stages: transparent transmission, transmission supporting Layer-2 (L2) switching and transmission supporting QoS of Ethernet services.

    After long time development MSTP has formed three systems: Ethernet over SDH (EOS), Resilient Packet Ring (RPR) embedded MSTP and Multiple Protocol Label Switching (MPLS) embedded MSTP. They have different characteristics, but they all go forwards in the direction of easier commissioning, simpler maintenance and efficient transmission.

2 ZTE´s Solutions to MSTP Systems

2.1 ZTE´s EOS
The L2 switching function is an outstanding characteristic of the EOS technique. Based on Ethernet link layer, it switches data frames on point-to-point links between one or more user Ethernet interfaces and one or more SDH Virtual Containers (VCs). MSTP with L2 switching function greatly improves multi-user/multi-service bandwidth sharing and isolation. Based on the relevant standards in the industry, the EOS technique used in ZTE´s MSTP system expands and improves many functions.

    The followings are the important characteristics of ZTE´s EOS:

• It employs Point-to-Point Protocol (PPP), Link Access Procedure SDH (LAPS) and Generic Framing Procedure (GFP) encapsulation modes, flexibly selects Network Management (NM), protects network equipment investment, and facilitates interconnection.
• All equipment in existing networks uses standard virtual concatenation and Link Capacity Adjustment Scheme (LCAS) technique. Delay compensation is up to 32 ms that is equivalent to 6 400 km.
• It first supports the convergence from Fast Ethernet (FE) to Gigabit Ethernet (GE) services with the longest operation time in the network.
• One board, with diversified usage, may be used to implement transparent transmission, as well as convergence and switching. This improves the flexibility of networking.
• The bandwidth of the transmission link can be configured through NM. Bandwidth adjustment implements
  non-damage ser vices.
• It supports VC-12-Xv/VC-3-Xv/VC-4-Xv mapping.
• According to the SQ number, it supports automatic sequencing, which simplifies manual configuration during the interconnection between different vendors.
• With GFP encapsulation, it supports FCS32 self-identification, which simplifies manual configuration during the interconnection between different vendors.
• It supports multiple service isolation mechanisms, such as link isolation of Virtual Connection Gateway (VCG), isolation of Virtual Local Area Network (VLAN) and extended isolation of VLAN.
• It supports dynamic multicasting based on the Internet Group Management Protocol (IGMP).

2.2 ZTE´s RPR-embedded MSTP
The existing Ethernet technology is connectionless and lacks adequate QoS processing capability. In order to introduce QoS into Ethernet services, it is required to add an intelligent adaptation layer between Ethernet and SDH. With an embedded RPR, ZTE´s MSTP may process the QoS requirements of Ethernet services, allow scalability, and support such functions as multipoint-to-multipoint connection, user isolation, bandwidth sharing, Ethernet service QoS, SLA enhancement, congestion control, fair access and ring protection on service layer.

    The followings are the important characteristics of ZTE´s MSTP with embedded RPR:

    (1) Access to Ethernet
    There are eight FE interfaces and one GE interface at users´ side, which can implement the ring-level convergence from FE to FE, from FE to GE, and from GE to GE. With a maximum of 2.5 G bandwidth, one backplane can transmit bi-directional 155 M-2.5 G services in the ring. The bandwidth of the RPR can be configured as required. The RPR also supports LCAS.

    (2) Powerful Traffic Supervision Function
    It can set traffic supervision parameters of each service with supervision granularity of 20 Kb/s.

    (3) Powerful Service Classification Function
    It can classify services according to the VLAN and port. It also supports the setting of 1 K traffic flow in RPR. Multiple A0, A1, B and C services are allowed in one RPR, and the bandwidth distributed to them depends on their own situations.

    (4) Fast Service Provision
    It supports automatic topology discovery, which makes the network more intelligent. Service commissioning is simple and fast. New services only require the configuration of source and sink nodes instead of the configuration node by node and circuit by circuit, greatly simplifying service configuration and upgrade. It supports hot swapping at the nodes and selects the ring in accordance to the shortest route.

    (5) Automatic Discovery and Correction of Protection Mismatching
    It supports Wrapping and Steering protections. The delay can be set to avoid the conflict of protection switching between SDH and RPR layers. It can automatically discover protection mismatching between the nodes in the ring, and then change the protection mode in the overall ring into steering, which avoids possible service disconnection caused by protection switching.

    (6) Fair Algorithm
    It adopts patented fair algorithm. The bandwidth of the ring can be fairly shared. Convergence is fast and bandwidth fluctuation is small. The fair algorithm is applied to the class-C service and Excessive Information Rate (EIR) B service. It uses the fair frame to control ring traffic of EIR B and class-C services at the local nodes and
upstream nodes. Fair algorithm helps implement the fair access of services at different nodes.

    (7) Assignable Service Connection
    Services can be connected through automatic switching. They can also be connected by statically configuring a destination site, which will fulfill point-to-point service transmission in RPR, prevent service broadcast from wasting bandwidth and ensure secure transmission of the services.

    (8) Assignable RPR Transmission of Services
    Services may automatically select the RPR transmission. They can also be set manually to be transmitted in the ring. The network traffic can be planned according to the actual situation in the network, and reasonably dispatches the traffic flow in the ring and improve bandwidth utilization of the ring.

    (9) Super-large Capacity of Media Access Control (MAC) Addresses
     One site can support at most 64 K MAC learning. It avoids unnecessary frame flux and reduces bandwidth waste during the establishment of a complex network.

    (10) First Introduction of Calling Identity Delivery (CID) User Domain into RPR
     It introduces the CID user domain into RPR, and implements double isolation of the user domain＋VLAN ID. It can isolate services of the same VLAN in different VPN domains, and implement Ethernet Virtual Private Line (EVPL) and Ethernet Virtual Private Local Area Network (EVPLAN). It supports Q-in-Q function and provides L2 VPN service, which resolves the VLAN shortage in IP Digital Subscriber Line Access Multiplexer (DSLAM).

2.3 ZTE´s Achievements on MSTP Standardization and Product Development
ZTE always contributes to the study of MSTP standards. Up to now, it has submitted to ITU-T several proposals on MSTP. Out of them, the following proposals were directly accepted:

• Proposal for Multi-Path Transmission of Ethernet over Transmission Network
• Impacts of Virtual Concatenation on Disruption Time of Services
• Network Management Policy of Automatic Switching Optical Network (ASON)
• Proposal for Ethernet Private Line (EPL) and Ethernet Private Local Area Network (EPLAN)
• Proposal for General Data Link Sub-layer
• Proposal for the latest version of G.ethsrv 
  

    Moreover, ZTE has drafted number of national standards on MSTP for China，including "Technical Requirements of SDH-based MSTP" , "Test Specifications of SDH-based MSTP", "Technical Requirements of MSTP Embedded with RPR" and "Test Specifications of MSTP Embedded with RPR".

    In China, ZTE´s MSTP equipment participated in numerous tests and certifications sponsored by authority institutes and operators, and passed all of them with good performance.

• June 2002: ZTE succeed in the test of metro transmission equipment sponsored by China Mobile, and became one of the vendors recommended in the Metropolitan Area Network (MAN) establishment of
  China Mobile.
• September 2002: ZTE succeed in the centralized test of metro MSTP equipment, sponsored by Shanghai Branch of China Telecom. ZTE, together with other two vendors, has been selected to take part of the simulation test at the stage 2 and passed the test in February 2003.
• April-July 2003: ZTE succeed in the centralized test of metro MSTP equipment sponsored by China Telecom, and its products were listed in Class A.
• June 2003: ZTE and two other MSTP vendors participated in MSTP interconnection test of Guangdong Branch of China Telecom. The test achieved great success and attracted mush attention in the industry.
• February 2004: ZTE succeed in the test for MSTP type selection sponsored by China Mobile.

Manuscript received: 2005-06-27