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One way to optimize link aggregation load balance base on local preference

IP.com Disclosure Number: IPCOM000237301D
Publication Date: 2014-Jun-12
Document File: 6 page(s) / 120K

Publishing Venue

The IP.com Prior Art Database

Abstract

This invention provide a method to save stack link bandwidth and make full use of port channel bandwidth in stacking topology. All stacking units maintain a token bucket for local port channel members separately. When packets come to a unit, it will request tokens from local port channel member links. This behavior allow each unite could use maximum bandwith on stack links.

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One way to optimize link aggregation load balance base on local preference

Stack switch:

Some switches supported stacking technology. It allows several switches, which linked by special cable or standard network cable could be formed as one switch. One switch, we call it master switch; will control all switch's ASIC chip. The stack link

Portchannel (trunk) on stack switch

Think about a scenario: a link aggregation, such as LACP or static portchannel members distribute on different members of stack and at same time, these switch need forward varies streams to this link aggregation group. Base currently aggregation portchannel algorithm, it will use HASH to calculate each stream base varies metric such as layer 2 / layer 3 source / destination address and protocol type or port numbers(layer 4 metrics). Under this condition, traffic may distribute to portchannel which on different stacking member switch . Also, the traffic will pass through stack link. For optimize traffic, the traffic pass through stack link will consume its bandwidth. Traffic forwarded to local portchannel member ports is the better way rather than follow regular portchannel algorithm .

Local preference is a way to forward this traffic to local portchannel members . If user enabled it, all known unicast will be forwarded to local portchannel members even these ports will have congestion. That is a problem for these traffic, if traffic rates above total bandwidth on local ports, it will be discarded. And this problem can't be walked around if user enabled local preference.

This invention is trying to provide a method to save stack link bandwidth and make full use of port channel bandwidth in stacking topology. All stacking units maintain a token bucket for local port channel members separately. When packets come to a unit, it will request tokens from local port channel member links:

1) If the tokens are enough, then all packets will be hashed and forwarded through local member links.

2) If the tokens are not enough to forward all packets, then the left packets that haven't get tokens from local will be hashed and forwarded on all port channel member links except local member links.

Traffic forwarding paths are illustrated in Figure 1.

1


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Figure 1 Traffic Forwarding Path


Through this way, the bandwidth of stack link can be saved. At the same time, bandwidth of port channel can be fully used.

As the figure 2 flowchart shown, the unit will perform 2 steps judge before it decide if forward unicast traffic via local preference. First it will check if traffic egress port is a portchannel port. Next, it will check if the unit has portchannel m...