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NE40E V800R010C10SPC500 Feature Description - Virtual-Cluster-Chassis 01

This is NE40E V800R010C10SPC500 Feature Description - Virtual-Cluster-Chassis
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Overview of Virtual Cluster

Overview of Virtual Cluster


Virtual cluster is a many-to-one virtualization technology, which can form a routing system from multiple common devices connected through a switching network, while performing the same as a single logical router to all external appearances.


As the Internet has developed rapidly and service models have undergone various changes, requirements have increased for the computational capability, forwarding performance, and port density of core backbone network devices. Traditional routers are faced with insurmountable obstacles in terms of reliability, performance scalability, capacity expansibility, and service scalability, and as such have been unable to satisfy the next-generation Internet development requirements. Super-core nodes have already become a service development bottleneck for telecom operators.

Therefore, to increase core layer device capacity and scalability, a simpler and easy-to-maintain network structure that meets core switching and interconnection network requirements is used, addressing the problems of greatest concern to customers. Using current technologies, there are three ways to solve the capacity problems that affect core devices:

  1. Single device capacity expansion

    The first way is to increase the number of slots on the chassis of each router and enlarge the capacity of each individual interface. Although current industry router interfaces can reach a rate of 100 Gbps, and will attain higher speeds in future, they nonetheless suffer from the limitations of single devices, such as microstrip processing, power consumption, and crosstalk, as well as alarmingly high R&D costs. Therefore, this solution is severely limited.

  2. Routing interconnection

    The second way is to extend multiple routers through routing interconnection. This requires the use of many additional high-speed interfaces, increasing the interconnection link overhead, and introduces issues with addresses, protocol neighbors, routing entries, and extending convergence time, among others. In this way, networks become more complex and harder to maintain, while traffic between these multiple devices cannot be balanced. Therefore, this way is only suited to deployment on a small scale.

  3. Multiple router clusters

    The third way is to use cluster technologies across multiple routers. This makes maintenance easy and does not increase network complexity, using more cost-effective means to meet rapid service growth, network performance, and capacity improvement requirements. Additionally, multiple router clusters realize larger-capacity core-layer devices and lower network construction and maintenance costs in compliance with network requirements, leaving a wide space for future growth.

There are two types of router cluster technology: physical clusters and virtual clusters.

  1. Both are horizontal clusters, consisting of two or more devices composing a single logical device that appears on the network to be a single router.
  2. The difference between the two lies in the different technologies they use to form the cluster.

    The physical cluster model supports multi-chassis clusters such as cluster central chassis (CCC) and multiple cluster line-card chassis (CLCs), as well as clusters comprised of two back-to-back chassis. The virtual cluster mode does not support multi-chassis clusters, instead only supporting clusters comprised of two back-to-back chassis. Therefore, in the following comparison, only clusters comprised of two back-to-back chassis are used as examples.

    • A physical cluster consists of two backbone routers connected to one another through a dedicated board and dedicated cables. Advantages: dedicated hardware ensures unblocked connection, dedicated hardware fault detection mechanism ensures high fault protection performance. Disadvantages: dedicated hardware is expensive and requires that the chassis be close to one another.
    • A virtual cluster consists of two edge routers connected to one another through a common interface board and an inter-board trunk. Unlike physical clusters, this router cluster technology can be blocked and so requires users to properly plan interconnected bandwidth. Inter-chassis connection fault detection and switchover performance is poor in comparison to a physical cluster, being equivalent to that of a common trunk. However, because it lacks dedicated hardware, it is inexpensive and the chassis can be further away from each other than with a physical cluster.

Due to the preceding factors, the two router cluster technologies are applied differently. In general, physical clusters are used for backbone networks, and virtual clusters are used for DC egress and metro networks.


Virtual cluster cannot only be used to expand the capacity of routers on the live network and increase their forwarding capacity. It can also be used to replace the traditional two-node cluster protection, thereby greatly simplifying network design, in turn reducing network O&M manpower and costs.

Updated: 2019-01-03

Document ID: EDOC1100055054

Views: 2449

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