topic Re: Linux Virtual Server in Operating System - Linux

Linux Virtual Server

Marco_113 — Fri, 01 Dec 2006 09:18:00 GMT

Hi all.
I've a question about Linux Virtual Server.

I've configured a balancer with NAT and works fine.

The real servers are IIS with some application.
My probelm is:

1)The client of the application is an entire Network in INTERNET natted with one public IP.

2)I need to setup a persistence to the session of the application.

So, how can i solve the problem that if i apply persistence, i loose the balancing because of the requests come from the same IP??

Thanks in advance ,
Marco

Re: Linux Virtual Server

Ivan Ferreira — Fri, 01 Dec 2006 09:35:57 GMT

Can you graph your network? is something like:

Internet (Clients)
|
Nat Box
|
| (Private)
LVS
|
Real Servers

Maybe you can configure a NAT POOL in the "Nat Box" so you have a pool of addresses connecting to the LVS.

Re: Linux Virtual Server

Marco_113 — Fri, 01 Dec 2006 09:40:38 GMT

Yes the network is:

Clients
|
Gateway (NAT box)
|
Internet
|
Balancer
|
Real Servers

But i cant adminisrate the Nat Box.
Thanks

Re: Linux Virtual Server

Matti_Kurkela — Fri, 01 Dec 2006 09:55:19 GMT

Many load balancers actually use the source and destination port numbers in addition to the IP addresses to identify individual sessions. According to the documentation, the IPVS component of the Linux Virtual Server works like this.

Any TCP or UDP connection has two port numbers associated with it: a source port number and a destination port number. There can be several connections to a single _destination_ port number, but the _source_ port number cannot be unique among connections coming from any one IP address.

(This means the source port number is usually dynamically allocated and useless for firewalling, but very useful to load balancers.)

A good load balancer might also be able to handle several TCP connections with identical source and destination IP addresses _and_ port numbers, by keeping track of the TCP sequence numbers of individual connections. UDP does not have sequence numbers as such, so this method is not useful for UDP.

If you're using the KTCPVS component of the Linux Virtual Server, it can implement the persistence using HTTP session cookies. This is completely independent of any network connection properties, so the presence of NAT will not affect it.

Re: Linux Virtual Server

Marco_113 — Fri, 01 Dec 2006 10:27:38 GMT

Thank you Matti.
Do you know where i can find some configuration example of source hash table with different ports??
Thanks again
Marco

Re: Linux Virtual Server

Marco_113 — Fri, 01 Dec 2006 10:42:15 GMT

Excuse me Matti,
can you tell me where can i understand reading LVS documentation that the different source ports is natively supported?
Thank you very much for your help
Marco