Main technical standards of GE switches commonly used by experts

The main technical standards of GE switches commonly used by experts. When a user encounters a problem when using GE switches, others have provided some professional answers, but they are not very detailed, there are still many questions about the gigabit switch technology. We hope that experts can provide some wonderful technical solutions.

Specification, 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 no-blocking Gigabit ports quantity L2 packet forwarding speed L3 packet forwarding speed routing quantity backplane capacity the main indicator for measuring the capacity of a Gigabit Switch is the backplane capacity of a Gigabit Switch, the Unit is GbPs. One gigabit switch 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 switches are designed to provide gigabit connections to computer servers, while the communication speed of the 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 GE switches, what really measures the capability of a Gigabit Switch is the number of non-blocking Gigabit ports that it can switch.

For a gigabit switch, the forwarding speed of the second packet is the forwarding speed of the Ethernet frame. Measured in PPS packets per second. Layer 3 packet forwarding speed Layer 3 packet forwarding speed refers to the speed at which the Gigabit Switch forwards Layer 3 protocol packets, 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 Gigabit 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 Gigabit Switch that uses a centralized route, the forwarding speed of the layer-3 packet is usually not equal to the packet forwarding speed of the layer-2, 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 larger the number of routes supported by the route table of a gigabit switch, the larger the network topology is. The typical man Gigabit Switch has a route of 64 K/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 a Gigabit Switch is non-congested. A Gigabit Switch must meet the following requirements to achieve true non-blocking. The backplane is a non-blocking structure. The common algorithm is that if the backplane capacity is greater than or equal to the number of ports × port rate × 2, the routing switch is non-blocking on the backplane.

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. Layer-3 packet forwarding line speed. The algorithm is that if the layer-3 packet forwarding rate of the chassis is equal to the number of Gigabit ports × 1. 488 Mpps, the layer-3 switch can achieve line speed.

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 Gigabit Switch cannot achieve the overall speed.

Another case is that the backboard 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 Gigabit Switch has a bottleneck. It should be clarified that the congestion and congestion described in this article are two different concepts in Ge switches.

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 defects in the internal structure of the Gigabit Switch. The communication speed of a single port cannot reach the full speed. This problem cannot be avoided through the Streaming Protocol. 4 Conclusion The Gigabit Ethernet 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.