Requirements for non-blocking Gigabit route switch technology

The gigabit router switch technology must meet several requirements without blocking. The gigabit router switch technology provides a detailed description of the requirements for non-blocking. This is a common problem. But how can we learn the Gigabit route switch technology more precisely to facilitate our work?

Standard for selection of Route switches and five main standards for routing switch models the actual work of radio/TV departments in selecting Gigabit routing switch technology for building a broadband IP MAN, this article lists five major selection criteria for the radio/TV department's reference. Based on these five selection criteria, we can basically compare the performance of the route Switches of different manufacturers: * backplane capacity * Number of non-congested Gigabit ports * Second-layer packet forwarding speed * Third-layer packet forwarding speed * Number of routes.

Backplane capacity. The main indicator for measuring the size of a route switch is the backplane capacity of the switch. The unit is GbPs. 3.1.2 no blocking Gigabit ports quantity j One gigabit route switch technology can exchange or route multiple Gigabit Ethernet ports, however, the maximum number of Gigabit Ethernet ports it supports does not mean that it can switch all these Gigabit ports at a non-blocking line rate.

The reason is that some Gigabit routing switch technologies are designed to provide gigabit connections to computer servers. However, the communication speed of gigabit NICs on existing computers is limited by the computer bus, far less than 1000 MbPS, generally, it is 300 ~ 400 MbPS. Therefore, it is not necessary for these servers with a Gigabit Ethernet card to provide a 1-gigabit line rate switch.

However, some manufacturers' products tend to shy away from this design goal and publicize the maximum number of Gigabit ports supported by the Gigabit route switch technology, what really measures the capability of the Gigabit router switch technology is the number of non-blocking Gigabit ports that it can switch. 3.1.3 layer-2 packet forwarding speed for gigabit route switch technology, the layer-2 packet forwarding speed is the speed at which Ethernet frames are forwarded.

Measured in PPS packets per second. Layer-3 packet forwarding speed Layer-3 packet forwarding speed refers to the speed at which the layer-3 Protocol packet is forwarded by the Gigabit route switch technology, such as the speed at which IP addresses or IPX packets are forwarded. Measured in PPS packets per second. It should be noted that the second-layer packet forwarding speed and the third-layer packet forwarding speed are two different concepts.

Many manufacturers usually only pick up the packet forwarding speed, but do not clearly distinguish whether it is the second layer or the third layer of the packet forwarding speed. For a route switch using a distributed route, the forwarding speed of the second packet is generally equal to the forwarding speed of the third packet. For a routing switch that uses a centralized route, the forwarding speed of the layer-3 package is usually not equal to the packet forwarding speed of the layer-2 route, because the centralized route requires a separate routing module to forward the layer-3 packet, the second layer of packet forwarding is carried out in each Gigabit interface module.

The number of routes. The larger the number of routes supported by the route table in the route switch, the larger the network topology is. The number of routes supported by the typical man route switch is 64 K per port. It should be clarified whether the number of routes claimed by the manufacturer is the number supported by each chassis or port. Generally, the number of routes per chassis is equal to the number of ports × the number of routes per port.

In the current Internet, the route table size of the backbone router that actually runs the BGP-4 is about 77 K, and it is growing slowly. The slow growth rate is mainly due to the adoption of CIDR technology. For a metropolitan area network routing switch, the 64 K route table capacity can meet the Metropolitan Area Network requirements for a long time in the future.

It is determined that the Gigabit router switch technology is non-blocking. A Gigabit router switch technology must meet the following requirements to achieve true non-blocking. 1) The backboard is non-blocking. The common algorithm is that if the backboard capacity is greater than or equal to the number of ports × port rate × 2, the routing switch is non-blocking on the backboard.

The second layer packet forwarding line speed. The algorithm is if the second layer packet forwarding rate of the chassis is = the number of Gigabit ports x 1. 488 Mpps. In this case, the route switch can establish a line when performing Layer 2 switching. 3) layer-3 packet forwarding line speed. The algorithm is if the layer-3 packet forwarding rate of the chassis is = the number of Gigabit ports x 1. 488 Mpps, so this route switch can achieve line speed when performing layer-3 switching.

There are many manufacturers whose product data meets the second-and third-layer line rate standards, but they do not meet the backboard non-blocking standards, this indicates that the second-and third-layer line speeds are obtained when data packets are not exchanged with backweights. If a large number of data packets need to be forwarded through the backplane, therefore, this routing switch cannot achieve the overall speed.

Another case is that the backplane meets the non-blocking requirement, but the packet forwarding rate on the second and third layers does not meet the overall speed standard, which indicates that the packet forwarding module of the route switch has a bottleneck. The congestion and congestion mentioned in this article are two different concepts in the routing switch.

Congestion occurs when multiple ports send data to one port at the same time, because the speed of the receiving port is less than the sum of the speed of multiple ports, data packet loss or decreased transmission rate, this problem can be controlled through the standard 802.3x traffic control protocol. Blocking is caused by a defect in the internal structure of the switch, and the communication speed of a single port cannot reach the full speed rate. This problem cannot be avoided through the Streaming Protocol.

In conclusion, the Gigabit route switch technology is becoming increasingly mature. In addition to its original compatibility, broadband, low cost, and excellent support for IP addresses, It is enhancing its reliability and scalability. In the current trend that radio/TV broadband MAN hosts IP services, Gigabit Ethernet is the first choice for broadband MAN construction.