CN1484413A - Method for realizing polylink flow equalization - Google Patents

Abstract

This invention discloses a method for realizing balance of aggregate link flow including the following steps: receiving a single broadcast data packet, if there are matched items in the address list, then they are forwarded if there is no matched address item, it is sent to an address study module which forecasts the future flow of each port according to its historical flow information to forward the said data packet via the port with the least flow in the future and renew the address list, broadly applied in an aggregate link bound by multiple physical links and a logic link between network devices, overcoming the shortcoming of unbanlanced loading for different ports decided according to certain bits of a data packet address.

Description

A kind of method that realizes polylink flow equalization

Technical field

The present invention relates between the network equipment method that many physical links are bundled into the polylink flow equalization of a logical links.

Background technology

Switch and switch can use the physical link more than two to connect between switch and the server.The benefit of doing like this is to have increased bandwidth, and the bandwidth of link aggregation equals the summation of the physical link bandwidth of polymerization.High reliability, when wherein certain bar physical link broke down, switch was discerned the inefficacy link automatically and is stopped to transmit information from this link, selected other links to proceed to transmit simultaneously.One or more physical link lost efficacy in the trunk, can not influence the connectedness of two equipment, and just link bandwidth descends along with the increase of stale link way, so the link aggregation technology can improve the reliability of trunk.Load balancing, link aggregation technology have a frame distribution algorithms, can carry out packet according to the flow of each physical link selectively and send, and make the load balancing of each link.Physical connection can dispose or reshuffle when changing fast.

Switch generally has a plurality of ports, and its major function is the packet that a port receives to be forwarded in the suitable port of another one go.The basic principle that realizes the exchange of packet is such: store data form and a study module of being called address table in the switch.Address table comprises an address entries and a port item at least, and the packet that is indicated as a certain destination address should send from corresponding port.Switch at first extracts destination address information after receiving a unicast packet from a port, and inquiry in the table of location if can find corresponding list item, is then transmitted this unicast packet according to corresponding port inwardly, handles otherwise press broadcast packet.Meanwhile study module can be according to the source address that receives bag and source port study and scheduler list item.

The scheme that realizes link aggregation has been described at United States Patent (USP) 6049528.An address table is arranged in equipment, after receiving a packet, at first search address table,, then transmit this packet according to the corresponding port in the address table if there is corresponding list item in the address table according to destination address.If do not have corresponding list item, then handle according to broadcast packet.Address list item then is that the rule learning according to general switch obtains.Application No. is to have described similar system in 20020012340 and 20020010791 explanations, and the rule that its exchange is transmitted is the partial information according to the packet that receives, and promptly which port a few positions of destination address are decided from and transmitted.

All there is a problem in above-described method, promptly all is that several bits according to the address decide this address and which port are interrelated during address learning.This method just might make that the certain port flow is bigger, and other port flow is very little, produces the phenomenon of flow skewness weighing apparatus between each port.

Summary of the invention

The technical problem of solution of the present invention has provided a kind of method that realizes polylink flow equalization, has overcome to decide according to the destination address that receives packet merely to occur the uneven phenomenon of flow in the link aggregation that exists in the way of address list item.

The method of realization polylink flow equalization of the present invention comprises following treatment step:

Step 1 receives a unicast packet, if the list item that is complementary is arranged in the address table then transmit;

Step 2 is if the address entries that is not complementary in the address table then is sent to the address learning module;

Step 3, the address learning module is predicted each port flow in future according to the port history flow information;

Step 4 is selected the port of following flow minimum and this address is got in touch and the scheduler table.

The following flow of prediction port specifically comprises following treatment step in the described step 3:

A) adopt the regularly method of inquiry, the port that reads accumulative total in the counter every T second sends byte number, supposes that the result of the j time inquiry of port i is Cij;

B) calculate the j time preceding T of inquiry of port i Mean Speed of second, computing formula is:

$S_{i,j}=\frac{C_{i,j}-C_{i,j-1}}{T}$

C) adopt the weighted average of several time period flows of past to estimate following flow.

If adopt the following T of the volume forecasting of two time periods Mean Speed of second, predictor formula is:

S ' _{I, j}=α S _{I, j}+ (1-α) S _{I, j-1}0≤α≤1 wherein

α represents weight, and maximum is 1, the big more firm T in the past of the dependence more flow of second of then predicting.

Can choose T=5 second generally speaking, α is 0.8.

Adopt the method for realization polylink flow equalization of the present invention, can overcome in the past decides the forwarding port may make the unbalanced shortcoming of different port load according to a few positions of data packet addressed, make when transmitting packet more balancedly dispense flow rate on physical link, the bandwidth of utilizing physical link to provide more fully.This method also has simply, fireballing advantage.

Description of drawings

Fig. 1 is the situation that two systems (such as between two switches or between the switch-to-server) connect by many physical links.

Fig. 2 is a functional module that port has of switch or server.

Fig. 3 is that port is handled the flow process that receives packet.

Fig. 4 is the address learning flow process of the present invention's method of realizing polylink flow equalization.

Embodiment

Below in conjunction with accompanying drawing basic principle of the present invention is described.

Fig. 1 is the situation that two systems (such as between two switches or between the switch-to-server) connect by many physical links.The port one of system A to port 4 links to each other with port 4 to the port one of the B of system, and these 4 link aggregations are a logical links.Non-polymeric port does not draw in this figure.

The functional module of having drawn a port among Fig. 2.The port receiver module is responsible for receiving packet from port.The address learning module is carried out address learning and scheduler table according to the source address and the receiving port number that receive packet.Address table has then write down the result of address learning, shows with a certain address to be which port the packet of destination address should forward from.Under the situation that TRUNKING (relaying) is not set, the CPU software processing module does not participate in the address learning process.Packet forward module is according to the destination address inquire address table that receives packet and make forwarding decision.The port sending module is realized the transmission of packet.

Fig. 3 is that aggregation port is handled the flow process that receives packet.A port is after being set to aggregation port, and the address learning module no longer works.Any unicast packet that receives is delivered to packet forward module earlier, and packet forward module is inquired about in address table according to the destination address of bag, if found the list item of coupling in address table, then carries out normal packet and transmits.If there is not the list item of coupling in the address table, then broadcasts processing, and address message is sent to the CPU software processing module carry out address learning.The software address study module comes the scheduler table with the result of study.

Fig. 4 is the address learning flow process of the present invention's method of realizing polylink flow equalization.In order to realize the purpose of flow equalization, at first predict each port flow in future, and determine the result of study according to the flow of prediction.CPU receives address learning message, and this address message comprises information such as the source address of the packet that receives and receiving port number.Inquire about the flow of all available ports in the aggregation group, and predict the flow of following port, selecting a port conduct of flow minimum is the forwarding port of the packet of destination address with this address, and address table is upgraded.

Introduce the implementation method of the following port flow of prediction below more in detail:

All have the ability of port flow statistics in the switch, the hardware of switch provides some cycle counters of 32, and software can know that by read counter port accumulative total has sent the data of how many bytes.Can adopt the regularly method of inquiry, inquire about counter in second, suppose that the result of the j time inquiry of port i is Cij every T.

The Mean Speed of T second is before the port i the j time inquiry:

$S_{i,j}=\frac{C_{i,j}-C_{i,j-1}}{T}$

The flow in common port future has bigger correlation with flow in the past, so we can adopt over the weighted averages of flow of several time periods and estimate the flow in future.In the formula below, we are with the Mean Speed of the following T of volume forecasting second of two time periods in the past:

S ' _{I, j}=α S _{I, j}+ (1-α) S _{I, j-1}0≤α≤1 wherein

α represents weight, and maximum is 1, the big more firm T in the past of the dependence more flow of second of then predicting.To after the following flow of front port is made a prediction, when occurring a new address at every turn and need learn, we come the scheduler list item according to address itself, but the port of this new address and flow minimum is connected, and the scheduler table at us.In above-mentioned formula, we choose T=5 second, and α 0.8 generally can obtain effect preferably.

More than describe the method that adopts method of the present invention many physical links between two equipment to aggregate into a logical links and realize load balancing in detail.

Claims (4)

1. method that realizes polylink flow equalization comprises following treatment step:

Step 1 receives a unicast packet, if the list item that is complementary is arranged in the address table then transmit;

Step 2 is if the address entries that is not complementary in the address table then is sent to the address learning module;

Step 3, the address learning module is predicted each port flow in future according to the port history flow information;

Step 4 is transmitted this packet by the port of following flow minimum, and the scheduler table.

2. the method for realization polylink flow equalization according to claim 1 is characterized in that, the following flow of prediction port specifically comprises following treatment step in the described step 3:

A) adopt the regularly method of inquiry, the port that reads accumulative total in the counter every T second sends byte number, supposes that the result of the j time inquiry of port i is Cij;

B) calculate the j time preceding T of inquiry of port i Mean Speed of second, computing formula is:

$S_{i,j}=\frac{C_{i,j}-C_{i,j-1}}{T}$

C) adopt the weighted average of several time period flows of past to estimate following flow.

3. the method for realization polylink flow equalization according to claim 2 is characterized in that, can adopt the Mean Speed of the following T of volume forecasting second of two time periods, and predictor formula is:

S ' _{I, j}=α S _{I, j}+ (1-α) S _{I, j-1}0≤α≤1 wherein

α represents weight, and maximum is 1, the big more firm T in the past of the dependence more flow of second of then predicting.

4. according to the method for claim 2 or 3 described realization polylink flow equalizations, it is characterized in that can choose T=5 second, α is 0.8.

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