topic Re: Cisco CSS load balancing algorithm query in Application Networking

Cisco CSS load balancing algorithm query

danielng83 — Mon, 28 Mar 2011 03:35:35 GMT

Hi all,

I was looking at the following document on Cisco:

http://www.cisco.com/en/US/products/hw/contnetw/ps789/products_configuration_example09186a0080094964.shtml

And i have a query as to how this load balancing algorithm will work.

content LOCAL-C
VIP address 192.168.3.6
protocol tcp
port 81
url "//site-c.mycompany.com/*"
add service C-S1
add service C-S2
add service C-S3
add service C-S4
add dns site-c.mycompany.com
dnsbalance preferlocal
balance leastconn
advanced-balance sticky-srcip
active

If the first request from client A comes in and all sessions from client A are load-balanced to service C-S1(because of advanced-balance sticky-srip), does the "least connection" algorithm kick in and only selects C-S2,C-S3 and C-S4 for the next request that hits the VIP?

Also, how is the advanced-balance sticky-srcip determined? Does it use a /32 or a /24 subnet when evaluating the source IP? Or is there a way we can specify this?

Thanks in advance!!

Re: Cisco CSS load balancing algorithm query

yushimaz — Mon, 28 Mar 2011 05:11:24 GMT

Sticky feature works before the determination of balance algorithm such as least conn.

If the entry is listed on sticky table, CSS sends packet with this table.

If the request is not listed on the entry, CSS determins the destination with balance algorithm.

So, if client A accesses to the vip and C-S1 is selected, all request from client A will be

forwarded to C-S1. When the entry is purged from sticky table by sticky timeout, next

request from client A will balance with least conn algorithm.

Other client request (not listed on sticky table) will be selected least conn algorithm.

If access from client is only client A as below.

Next request from non-client A will be destined to C-S2, C-S3 or C-S4.

CSS11503# show service summary

Service Name State Conn Weight Avg State

Load Transitions

C-S1 Alive 10 1 2 0

C-S2 Alive 0 1 2 0

C-S3 Alive 0 1 2 0

C-S4 Alive 0 1 2 0

If there are many access from some clients as below.

Next request from non-client A( and the entry is not listed on sticky

table) will be destined to C-S1 since C-S1 is least Conn Load.

CSS11503# show service summary

Service Name State Conn Weight Avg State

Load Transitions

C-S1 Alive 10 1 2 0

C-S2 Alive 20 1 2 0

C-S3 Alive 20 1 2 0

C-S4 Alive 20 1 2 0

sticky-srcip is use /32 mask by default.

You can change the mask with sticky-mask config in content rule as below.

CSS11503-A(config-owner-content[test-test])# sticky-mask

Ip address mask in dotted decimal (x.x.x.x)

Please refer to the following URL regarding sticky mask feature.

http://www.cisco.com/en/US/partner/docs/app_ntwk_services/data_center_app_services/css11500series/v8.10/configuration/content_lb/guide/Sticky.html#wp1044272

Regards,

Yuji

Re: Cisco CSS load balancing algorithm query

danielng83 — Mon, 28 Mar 2011 07:24:46 GMT

Thank you very much Yuji!! Definitely helped cleared my doubts!