How the balance works for http/https in CSS?

Question

I want to understand how the balance works for http/https in the CSS.
As per doc,
- http/1.0=single URL per TCP connection
- http/1.1=persistent connection.
Q1. my understanding is http is stateless connection so needs TCP session for each URL. how the http/1.1 works with persistent. keep the same TCP session for a multiple URL request?
Q2. https is using single URL and continue processing until terminate the https instead of open another URL in the middle of transaction. in this case, I think the client can stick into same service based on the assumption the CSS support persistent. if then, no advanced sticky(ex, srcip) required?
Q3. looks below both are analogy. what's difference between them?
- balance srcip(same src IP to the same service)
- advanced-balance sticky-srcip
Q4. what's balance decision mechanism for "balance roundrobin" to distribute evenly? ex, in case of multiple URL request coming from same client. evenly distribute URLs?
Regards,

Answer 1

Hello,
first let me clarify 1 point.
HTTP/HTTPS are standards that are defined in RFC.
For HTTP/1.1 you can check the following RFC
http://www.faqs.org/rfcs/rfc2616.html
Therefore, the behavior of HTTP 1.1 is not defined by the CSS.
Q1- HTTP/1.1 simply keeps 1 TCP connection to send a received mutiplie HTTP request/response.
HTTP/1.0 will open 1 TCP connection for every HTTP request.
Q2- HTTPS is just HTTP over SSL.
So basically the same rule as above applies.
HTTP/1.1 can use 1 SSL connection for many HTTP request/response while HTTP/1.0 will use 1 SSL connection for each HTTP request.
Therefore, if you have customer using HTTP/1.0 you need some form of stickyness to guarantee that every connections will go to the same server.
Even if only using HTTP/1.1 you may need stickyness.
A user could disconnect and reconnect and require to be loadbalanced to the same server as before.
Q3- There is a big different between balance srcip and sticky-srcip.
The balance srcip simply hash the source ip address to find the destination server.
The problem of this method is that the loadbalancing is not guarantee to be evenly distributed between the servers.
With sticky-srcip, you use a normal balance method like round-robin, and then you create a sticky entry in a sticky table.
Next time this user comes back we first check the sticky entry to find the destination server.
The advantage is that it guarantess your users will be evenly distributed among the server.
Q4- roundrobin is applied to connection - not url [by default].
So if you have 2 users and they both open 1 connection, the CSS will send 1 connection to 2 different servers.
So each server has 1 connection.
If one user sens 10 URL and the other 1 sends only 1, one server will have 10 url to process while the other only one.
That's if you are using HTTP/1.1 and use persistent mode on the CSS.
You can break persistency and split the url.
I run out of space and time to explain you everything.
I suggest you go read the RFC or a book on HTTP.
Also read the CSS configuration guide.
There is much more you need to know if you want to take full advantage of the CSS like cookie, ssl offloading, L7 rules vs L3/4 rules, ...
Regards,
Gilles.