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HASA algorithm of load-balance for S9300 link aggregation

Publication Date:  2012-10-24 Views:  2 Downloads:  0
Issue Description
Topology information: server1====9300====server2 server dauble network adapter aggregation connecting to 9300, for increasing flow, server 1 send the flow that  original going server 2 to 9300 by two link load balance, 9300 need to average the flow to 2 links and send to server 2.
Server 2 connected to G1/0/18 and G1/0/21 of 9300, the flow sent from 9300 to server 2 only can be transmited on one GE link in practice, it cannot realize to enhance the flow.
Alarm Information

load-balance-profile boss
  ipv4 field sport        //It means hash algorithm of load balance base physic original port
#
interface Eth-Trunk2
port link-type access
port default vlan 32
load-balance enhanced profile boss
#
interface Eth-Trunk3
port link-type access
port default vlan 32
load-balance enhanced profile boss
Handling Process
It adjust to 1/0/24、1/0/25 port, whose corresponding physic port number is 39 and 38, calculation index is different, load balance realizing. It found that after connecting port of server 1 to G1/0/24 and G1/0/25 of 9300, the flow sending from 9300 to server 2 can be load balance to G1/0/18 and G1/0/21. Flow reached GE line rate, fulfil the demand of binding port for enhancing bandwith.
Root Cause
Then the flow sent from 9300 to server 2 only can be transmited on one of the G1/0/18 and G1/0/21 ports, it cannot realize load balance of sending to server 2.
Adjust the ports of server connecting with 9300 to G2/0/23 and G2/0/24, S9300 also cannot realize load balance.

After analysis of 9300 switch load balance hash algorithm, we know that:
According sport algorithm in ipv4 field sport: the later 3 bit of sport original physic port number calculate by exclusive OR and REM operation of 2 (trunk member ports number).
In scene, the key is the later 3bit of original physic port number, the beginning selecting port number of eth-trunk 2 is 1/0/23、1/0/19, whose corresponding physic port number is 25 and 17, binary numeral is 11001 and 10001, later 3bit is same, so the calculation result is same too, it cannot realize load balance according to original ports.
Then it adjust to 1/0/23、1/0/24 port, whose corresponding physic port number is 25 and 39, binary numeral is 11001 and 100111, last number is 1, after REM operation of 2, the result is same, it cannot realize load balance according to original ports too.
Suggestions
The ability of 9300 binding link load balance is stronger than8500 series switch, there are manifold modes of hash algorithm can realize the load balance, in practical using, it should confirm the algorithm feature.(feature of sport is realizing the packet accessed from physic port 1 go out only through physic port 2, load balance completely defers server sending packet, i.e. server sending packet is symmetrical, so packet forwarding is symmetrical.)

END