What is the future of the IP service router?

China's IP service routers are still developing rapidly. With the continuous development of the Internet, it also proposes that the emerging broadband technology must meet the carrying requirements of telecom services. Mobile Internet will become the main body of the next-generation Internet, And the next-generation mobile broadband network must be able to meet the requirements of Traditional Telecom and mobile Internet services at the same time.

The segmentation of IP and transmission of services will become the main line of network evolution in the future. In terms of access, the next generation of mobile access networks will evolve to LTE, and PON will become the mainstream technology for fixed broadband access. In terms of backbone networks, IPoverWDM/OTN networking has become mainstream and can meet service development needs for a long time. In terms of man, SDH/MSTP, Ethernet, and IP/MPLS technologies are all competing for the market, however, there are different limitations in broadband convergence and backhaul bearer applications. a ptn technology combined with transmission and data capabilities will enable the future of IP service transmission. Design Philosophy: efficient implementation of IP, telecom-level IP, and telecom-level is two major needs to promote the evolution of man. IP has two meanings. IP is used as encapsulation and Address Identification for both voice, data, and multimedia services; the IP address of a network means that both a mobile network and a fixed network will satisfy the requirements of the IP Service Router. The diversity of IP Services and the Burst Characteristics of IP service routers require the bearer network to have QoS and Statistical Multiplexing capabilities, the "rigid pipeline" technology, represented by SDH, cannot adapt to the future IP service load. In addition, the traditional man service is a typical aggregation service. The switching and routing functions are generally completed at the core or aggregation layer, while the P2P service and LTEX2 interface have the need for fullmesh networking, therefore, the demand for flexibility is also increasing.

On the other hand, IP-based services do not mean that all IP service routers are dedicated services. scalability, reliability, manageability, and service quality are still the basic requirements of man. For example, LTE requires that the one-way latency of S1 interface not exceed 5 ms, TD-SCDMA system requires that the accuracy of time synchronization signal is higher than ± 1. 5us, 50 ms protection switching capability is still an important indicator to measure the network reliability. Ethernet and IP technologies based on non-connection technologies face challenges in QoS, protection, and manageability. In recent years, carrier-class Ethernet (CE) and packet transmission network (PTN) have become a hot topic. CE focuses on describing the five features of Carrier-class businesses, while PTN focuses on describing the segmentation of the transmission network. The main technology of PTN includes MPLS-TP and PBB-TE. Its core concept is to adopt MPLS and Ethernet encapsulation and forwarding mechanism, retain the original packet switching and QoS mechanism, removes some complex layer-3 or layer-2 protocols, removes MAC address learning, spanning tree, flooding, and other Ethernet connectionless features, enhances OAM capabilities, and enables hierarchical management based on services and networks, in addition, the network protection capability is enhanced. In addition, to enhance the flexibility of the network, the PTN introduces a control plane to realize automatic resource discovery and connection, and implements controllable and manageable dynamic characteristics through a powerful management plane.

It can be seen that the PTN integrates the transmission and data capabilities to achieve IP-oriented and telecom-level connection while trying to remove some complex protocols and processing, reducing network complexity and costs. This design concept of PTN first reflects the advantages in man. First, at present, the convergence and access layers of man are still dominated by aggregation services, without the need for powerful routing functions. The statistical multiplexing and QoS capabilities of PTN can meet the needs of IP-based service development. Second, large man coverage and multiple nodes. establishing connections and protection through the network management can better meet latency, jitter, and Protection Switching time requirements. Third, the hierarchical OAM mechanism similar to SDH facilitates Fault Locating and improves network O & M capabilities. Fourth, PTN uses two-way LSP Technology to build Symmetric Networks, which facilitates the use of 1588v2 protocol to provide time synchronization. Fifth, the PTN can be introduced into the control plane to improve network flexibility and meet the bearer requirements of future businesses.

Layered Multi-Service Transmission Network Model MPLS-TP uses a layered network model, including pseudo line layer (PW), LSP tunnel layer (LSPTunnel) and section layer (MPLSSection ), the service path, transfer channel, physical link, and other logic functions are layered. By layering different logical functions in the transport network, the network topology and service topology are clearer, making O & M management easier and more efficient, and easy to implement fault isolation and alarm suppression functions, this effectively reduces the number of connections to be maintained by the transmission network.

The pseudo-line layer encapsulates services in a unified manner. It provides an end-to-end transparent transfer path during IP service router forwarding to implement multi-service transmission. The IP/MPLS technology has developed a complete set of business encapsulation methods. PTN adopts the PWE3 protocol defined by IETF to achieve the segmentation encapsulation of various businesses such as ethereum, TDM, and IP, the maintenance interface between the transmission network and the service network can be clearer, and the IP address and MAC packet header in the data network can be used as the transport network label, the effective isolation between the transmission network and the service network cannot be maintained.

The LSP tunnel layer is nested with multiple same-path PW service paths. The limitations of the physical link layer are shielded during the transmission networking process to implement bandwidth allocation, flexible scheduling, and end-to-end fault isolation. The MPLS-TP adopts the MPLStunnel technology which is widely used in the MPLSVPN network. The flow direction and traffic are determined during the transmission process to form the end-to-end transmission channel.

Non-blocking group switching system architecture to ensure high QoS requirements of IP service routers such as leased lines and voice, the new generation of PTN devices adopt a non-blocking group switching system architecture. QoS of A group network is first guaranteed by the system architecture of the device. The switching architecture of the group device can be divided into two categories: the non-blocking Crossbar cell switching architecture and the low-cost shared bus/shared memory architecture.

The main representatives of the non-blocking Crossbar architecture are high-end routers and ATM switches. The forwarding module performs fixed-length segmentation on each packet in the forwarding group. These fixed-length elements are restored to the complete packet after the non-blocking cell exchange in the Switching Module, the same-length meta-exchange eliminates the inconsistent latency of unequal packet processing, so it can ensure line rate forwarding on any port and implement strict business priority policies, qoS features such as latency, jitter, bandwidth, and packet loss rate are not affected by the forwarding performance of devices. Vswitches and low-end routers generally adopt shared memory or bus architecture, and their centralized storage and forwarding mechanisms have performance bottlenecks, bus conflicts or memory read time restrictions determine the delay and jitter (generally in milliseconds). packet loss exists and strict QoS priority cannot be guaranteed.

Perfect QoS mechanism for connection networking

End-to-End QoS requires connection-oriented networking technology. In the dedicated IP bearer network that carries high QoS services, in order to avoid the effect of traffic and flow direction disorder caused by dynamic routing on QoS, IP router adopts connection-oriented MPLS-TE technology, ensure the QoS of the IP Service Router through centralized Path Planning and Bandwidth Reservation. MPLS-TP fully inherits the connection-oriented characteristics of MPLS-TE, and establishes MPLSTunnel through centralized network management or control plane. In addition, the MPLS-TP is a static transmission pipeline, do not need dynamic route refresh, only by the link status change and IP service router configuration, this eliminates the impact of fault propagation and route Fluctuation Caused by Dynamic Route refresh.

End-to-end high-performance OAM Mechanism Implemented by hardware

The most prominent advantage of PTN is its high-performance hierarchical OAM Mechanism, which enables real-time and accurate fault locating in complex network topologies. Overcome the defects of IP/MPLS networks in fault detection, fault locating, and alarm suppression. The MPLS-TP defines the hierarchical OAM Packet Processing Mechanism for the pseudo-line layer, LSP tunnel layer and MPLS layer, through the support of layered network, the upper layer OAM information can be automatically inserted to the lower layer link in order, this provides a protocol basis for status transfer and alarm suppression. MPLS-TP defines complete OAM packets, such as CC & CV for connectivity detection, AIS packets used to suppress downstream and secondary alarms, RDI packets used for reverse plugging remote alarm indication to maintain two-way link status, and LB packets used as network maintenance means.

The ptn oam packet processing adopts hardware implementation, which significantly improves the processing performance. Traditional routers are implemented through software, and the performance is limited by the CPU processing capability. The number of LSP protection groups supported by high-end routers generally does not exceed 2000, the Metro Transmission Network requires tens of thousands of IP Service Router protection groups. Thanks to the well-defined OAM Fault Detection and transfer mechanism, PTN can complete fault detection within 10 ms and 50 ms failover performance requirements. MPLS-TP/T-MPLS defines a clear linear protection, ring protection function, can support 1 + 1, environmental protection and other network protection technology, adapt to the needs of various network topology.

End-to-End visualized and centralized network management

The PTN centralized network management system provides end-to-end functions such as IP service router configuration, fault locating, performance monitoring, and daily maintenance. The availability of the network management system is an important indicator for evaluating whether the PTN devices are mature and commercially available. End-to-End centralized network management is built on connection-oriented networking models and end-to-end OAM models. connection-oriented networking models can maintain a clear network topology between services and networks, business traffic flows can be planned and deployed. High-Performance OAM support can monitor the status of any node on the link in real time. Hierarchical OAM can effectively suppress secondary alarms and focus on Root-source alarms. In addition to static configurations of centralized network management, the PTN service can also be established automatically on the control plane to take advantage of the flexibility of mature IP routing protocols.

PTN development prospects with the development of 3G and full-service, the operator's demand for IP-based transmission solutions for man is imminent. The design concept of PTN fusion transfer and data capabilities has been recognized by a large number of operators and equipment manufacturers and is expected to become the mainstream technology of man. According to the current test and pilot cases, most PTN devices have multi-service bearer capabilities, and performance indicators such as latency, jitter, error code, and packet loss can meet the requirements. The 1:1 protection meets 50 ms switching, some manufacturers can well support the 1588v2 protocol, and the precision of the ground transmission time synchronization signal is higher than ± 1 Zs. On the other hand, the PTN equipment can not detect the performance deterioration and promote the replacement of SDH, does not support the ring network protection, and because the MPLS-TP OAM related standards are not perfect, mainly adopts the OAM mechanism of T-MPLS. In terms of network maintenance and management, the configuration and management capabilities of end-to-end IP service routers need to be enhanced, and operators also need to accumulate experience to develop QoS parameter configuration principles. It is believed that with the rapid development of PTN standardization and industrialization and the further maturity of technology, PTN will be first applied in man.