On Mon, 18 Oct 2010 20:50:02 +0200, Konrado Z <konradoz_at_partyinfo.com.pl>
wrote:
> Hello,
>
> I have to consider four scenarios:
>
> 1) http://img230.imageshack.us/img230/4172/52435275.jpg
> 2) http://img2.imageshack.us/img2/6708/42467335.jpg
> 3) http://img213.imageshack.us/img213/3600/77675899.jpg
> 4) http://img84.imageshack.us/img84/7221/12837089.jpg
> Host is connected only to one proxy (I think it does not matter to
> which one). But proxies servers are connetected to each other.
>
> The question is, on which proxy server the website requested will be
> cached (and why)?
> Unfortunately I do not have RAM memory enough to install two (or three
> in some cases) virtual machines with Squid, so I would much appreciate
> your answers.
This looks a lot like undergrad homework :P
Notice that cache storage can be suppressed at any Squid on a wide range
of criteria. So the answer to your question can change dependent on what
you want to configure. The answers below are using the assumption that all
proxies are storing everything cacheable which travels through them.
>
> My answers:
> 1)
> when 1&2 doesn't have website requested:
> - 1 & 2 cached the website
Yes. Everything going through #2 also goes through #1.
>
> 2)
> when 1&2 doesn't have website requested:
> - 1 or 2 /it depends where the host is connected/ requests the website
> and cached it
>
> when 1 has the website requested, but host is connected to 2:
> - 2 requests website from 1, and cached /two servers cached after all/
>
> when 2 has the website requested, but host is connected to 1:
> - 1 requests website from 2, and cached /two servers cached after all/
>
Yes.
With condition that special request types such as CONNECT (and for some
older squid any dynamic web pages) are not passed to siblings when direct
Internet access is available. These are usually non-cachable anyway so have
little impact on the storage. They require admin config intervention to use
the sibling.
> 3)
> when 1&2&3 doesn't have website requested:
> - the website is cached 3 and 1 or 3 and 2 /it depends where the host
> is connected/
>
> when only 3 has the website
> - the website is cached 3 and 1 or 3 and 2 /it is copied from 3/
>
> when 1 or 2 has the website
> - the website is cached only 1 or only 2 or 1 and 2 or 2 and 1 /it
> depends where the host is connected/
No. Simple join of scenarios (1) and (2).
- proxy #3 caches everything. Because all traffic flows through it.
- proxy #1 and #2 are exactly the same as scenario (2) with same reasons.
The fact that proxy #1 and #2 are connected to #3 instead of direct to
internet is not relevant to what gets cached.
>
> 4) the same situation as in 2
Yes.
Scenario (1) and scenario (2) are the basic units of cache hierarchy
design. Same as with Internet route design. The complexity comes when you
start limiting what requests can go where. Creating big loops, one-way
requests, non-caching, and peering routes.
Amos
Received on Mon Oct 18 2010 - 22:34:05 MDT
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