Alcatel Shanghai Bell: IP network transmission structure needs to be optimized

JasonYoo

Alcatel Shanghai Bell: IP network transmission structure needs to be optimized [Copy link]

Introducing intelligent optical networks to carry IP can effectively simplify the network structure, significantly reduce the overall investment cost of the network, and significantly improve scheduling capabilities, maintainability, reliability, scalability and service QOS.

With the rapid growth of IP services, the demand for network bandwidth has far exceeded that of traditional voice networks, which has greatly increased the capacity of the network. The capacity of each optical fiber has reached the Tbit/s level, and the nodes need to process dozens or even hundreds of wavelengths.

At the same time, the number of nodes has also increased several times, and nodes often need to be directly interconnected through optical waves, and the network topology MESH has become an inevitable trend. This new feature is also reflected in the fact that IP services have put forward higher requirements on the service scheduling capability, maintainability, reliability, and scalability of the bearer network. The suddenness and uncertainty of IP services require the network to have the scheduling capability of various service granularity levels to quickly provide services and optimize network resources; as the scale of the network expands, the maintenance and management of the network also face new challenges; in order to meet the QoS requirements of IP services, the bearer network must be able to provide services with different reliability levels, which puts forward new requirements for the reliability of the bearer network; as the scale of the network continues to expand, the network is also required to have good scalability to avoid the adverse effects of the new network on the original network.

IP network transmission structure needs to be optimized

Traditional IP networks are best-effort networks. They are positioned to provide basic Internet access services. There is no need to guarantee strict QoS, nor is there any need to consider the additional bandwidth required for fault recovery. Therefore, their bandwidth utilization rate may reach a very high level. The new generation of carrier-grade IP networks is required to become a unified multi-service packet transmission platform for voice, video, data services and new services that may appear in the future. The development of carrier-grade IP networks with QoS guarantees has become an inevitable requirement for operators.

The current IP network construction plan is to hierarchical data networks, carried by DWDM or directly connected through optical fibers. Multiple routers are required to transfer between the source and destination of IP packets, which will generate a large number of direct services, that is, services that are not added or removed locally but directly transferred (direct services can account for 60% of the total processing capacity of a core router). This will lead to a large amount of additional costs, and even the core routers with the largest capacity will soon face the problem of expansion. At present, the expansion of IP routers uses clustering. The interconnection of devices at the same location is expensive and often leads to internal congestion in the network. In addition, the core IP network adopts a dual routing backup (link backup, node backup) networking structure, which has led to a doubling of operators' network investment. Therefore, the current IP network is extremely lightly loaded, and the bandwidth utilization rate of backbone network links is only 10% to 30%. Designing a new cost-optimized IP network transmission structure has become a research hotspot in the industry.

Introducing ASON

Intelligent optical network technology is defined as ASON by ITU-T. It introduces dynamic switching and intelligent control capabilities into traditional static optical networks, thereby enabling the transmission network to evolve from a bearer network to a service network.

*Intelligent: Rapidly provide network services and new profit growth points, such as optical virtual private network (OVPN), traffic engineering (TE), triple play (TriplePlay) and other high ARPU value services; improve the survivability of services, effectively resist network multi-point failures, and truly achieve a carrier-grade service level of more than 99.999%;

* Standardization: Network interoperability in a multi-vendor, multi-operator environment is achieved by adopting standardized protocols and interfaces;

* Personalization: flexibly provide different service levels to meet the needs of the rapidly developing differentiated (Diff-Serv) services;

*Simplification: Automatically protect services and discover topology, reduce the workload of manual configuration, and minimize maintenance difficulty.

Simplified networking

With the booming development of P2P and P2MP services for video and data, IP services are transforming from centralized aggregation to evenly distributed services. Correspondingly, IP networks tend to be flat, with direct transmission channels connecting every two ROUTERs, forming a logical mesh network at the VC4 level, with core and aggregation integration and no strict stratification. This can avoid the emergence of super core nodes, simplify IP/MPLS network routing configuration and management, and routers no longer need to be configured with multi-hop routing. This structure can reduce maintenance costs and greatly improve network robustness.

IP router mesh interconnection can avoid a large number of direct services generated by intermediate nodes, but optical fiber or DWDM virtual fiber mesh direct connection to the IP layer is not easy to maintain, has high costs, and has low link efficiency. ASON can use VC4 as a particle at layer 1 to build a logical mesh network for IP and effectively fill the optical fiber link. Practical applications show that the direct link capacity requirement between most nodes in the network is less than 2.5Gbps.

Reduce overall investment costs

Considering that the market price of core routers with the same I/O ports is five times that of SDH equipment, ASON can provide direct connection channels at the VC4 level. The routers form a logical mesh network, and the 3-layer processing of direct services is transferred to the 1-layer, saving the capacity and ports of the routers (especially long-distance ports). ASON provides 1-layer protection/recovery, and the 3-layer routers do not need to reserve a large amount of capacity for service recovery, and there is no need for dual-plane (link, node) protection mode. Avoid router stacking and super core nodes.

In the traditional mode, IP network adopts multi-layer architecture, and direct services need to go through multiple hops to reach the destination, which consumes a lot of L3 resources of the intermediate routers. As a result, many backbone nodes need to be expanded. The cluster method is too expensive and will introduce congestion. In practice, only 3 to 4 interconnections are supported, and Terabit routers are even more expensive.

Using ASON to carry IP can significantly reduce the overall investment cost, especially the investment cost of routers.

Improving service QoS

The traditional IP network multi-layer structure introduces multiple hops and additional delays, which have a great impact on the QoS of some services, especially global VoIP communications (≥150ms). The 0.99998 end-to-end service reliability (eg VoIP) requires higher backbone network reliability, which is difficult to achieve with current IP networks.

ASON-based IP networks can improve service QoS by facilitating fault location and improving network management capabilities; reducing service impairment time (through Layer 1 protection/recovery); using Layer 1 (rather than Layer 3) processing to reduce latency (nodes and links), suppress jitter, and reduce packet loss rates; and reducing the frequent updates of router routing tables due to faults.

New business, new applications

ASON can provide BOD services (UNI1.0, 2.0), dynamically request bandwidth through UNI interface, improve network utilization, avoid the traditional maximum service configuration (port, matrix) mode, save the capacity and port of routers, and improve the bandwidth utilization of transmission network. ASON can allocate corresponding OVPN for connections between IPTV, NGN, Softswitch, 3G bearer, IDC interconnection, and public INTERNET service nodes, sharing the same physical transmission network.

With the rapid growth of IP services, the demand for network bandwidth far exceeds that of traditional voice networks, which greatly increases the capacity of the network. The suddenness and uncertainty of IP services will require the network to have wavelength-level scheduling capabilities to quickly provide services and optimize network resources. Through software upgrades, the VC4 matrix is converted into an ODU matrix, thereby providing cross-connection capabilities for 256 wavelength channels.

Network maintenance

ASON provides more powerful fault detection capabilities, making network maintenance easier and reducing maintenance costs. ASON resists multiple link failures, greatly improving network robustness. ASON provides end-to-end channel scheduling capabilities, making service provisioning faster.

ASON supports a variety of protection and restoration types and service priority levels, can resist various link failures, and provide effective bearer for IP services with different QOS requirements.

Combining protection and recovery, PRC provides permanent 1+1 protection. Two NORMAL circuits are established between the source node and the destination node at the same time, which are the primary and backup routes, and these two circuits will not pass through the shared risk link group (SRLG). When a network failure causes a route failure, the service will automatically switch to another route within 50ms, and the recovery mechanism will be started at the same time to find and establish another protection route. After the network failure is finally restored, the primary route and the backup route will return to the original NORMAL route. Improve the reliability of the network layer: <50ms, the routing table will not be changed due to link failure.

1+1 protection provides switching in less than 50ms when a fault occurs.

The recovery mechanism (rerouting) temporarily creates a protection path to protect the service. The recovery mechanism is divided into two types according to whether the backup route is calculated in advance: guaranteed GUARANTEE recovery (pre-calculation of protection route) and source SBR-based recovery (calculation of protection route after the main service is interrupted).

Based on the definition of network protection type, the network can customize up to 5 priority levels. When a failure occurs and affects multiple services at the same time, high-level services are restored first. If the network has insufficient idle resources, high-level services are restored and low-level services are lost. When there are no idle resources, high-priority services can preempt resources of low-priority services. When the network failure is repaired, multiple services of different priorities can return to the initial route.

In summary, using ASON to carry high-quality IP networks can simplify networking, reduce overall investment costs, improve service QoS, and simplify network maintenance and the introduction of new services and applications.