I've just started learning ACNS and I'm a bit confused about some of the setup/design options. I'm just reviewing the documentation and do not have the kit yet so I can't try things out the moment. This is what I have found out so far and think is correct although might be completely wrong.
1. In a scenario where ACNS is used only for simple web caching I think WCCP would only be configured on the remote branch router with following configuration.
ip wccp enable
ip wccp version 2
ip wccp web-cache
ip wccp redirect-list 1
access-list 1 permit 10.1.1.1 (the origin server)
desc Remote LAN facing interface
ip route-cache same-interface
ip wccp web-cache redirect in
the CE would have the following:
wccp version 2
wccp router-list 1 192.168.0.55 (the WCCP server - router)
wccp web-chache router-list-num 1
In this setup I would not need the root CE in the root location. Also WCCP would only be configured only on the remote branch router. The only situation where the CE and WCCP would be used in the central location (the LAN where the origin servers are) would be either in reverse proxy (for the origin server offload) or if we wanted to control and cache traffic from the central location to the internet (together with websense for example). In this scenario, traffic headed for the internet would be intercepted and redirected to the CE.
Normally the central location users would be accessing the intranet origin server directly. In other words central location users would not be using the ACNS network.
2. The root CE is only required if pre-positioning is used. The root CE for the channel is the only CE authorized to go directly the origin server. Once the content is acquired by the root CE, it is then distributed (via unicast or multicast) to the other CE in the channel (schedule and bandwidth can be configured). Also in this WCCP would not be needed in the central location.
The root CE is usually installed in the central location to have high bandwidth access to the origin server. It is not installed in the remote location (although I guess it could be if the remote location had reasonable bandwidth) and cannot function as both regular CE and root CE (cannot distribute content to itself). If I designated one of the remote CE and the root CE, would I need another CE at the location?
3. Generally speaking the whole idea behind the ACNS is content distribution and pre-positioning. For caching and WAN optimization WAAS would be recommended with DRE, TFO and compression + CIFS caching.
4. The content pre-positioning can be restricted by disk space on the CEs. If a given object is not pre-positioned, normal web caching will kick in, if configured.
5. The WCCP configuration is the same for web caching and propositioning (it is merely used for redirection)
I know it might sound like basic stuff but would be very grateful for any answers/confirmations. I understand that it's a bit lengthy :)
Let me see if I can comment by number here. First off, all of your comments on #1 are correct with the exception of mentioning the root CE. In straight transparent caching where you have a router and CE at a branch location running wccp, you do not need a root ce. This would be simply web caching to the internet.
In #2, this is all correct. Root CE would be at the home location along with a CDM for CE and channel mgt. You would probably want to put another CE in the same location as the root so it will become the root CE in case of a failure.
The only thing that is missing in this discussion is the use of a Content Router. This is where you have a coverage zone file on a Content Router. Basically what happens is a client requests content. All requests hit the Content Router first and then based on the coverage zone file, the client is then sent to the correct CE for content. This is the most complex use of ACNS.
#3 is correct. In #5 you do not need wccp all the time when using preposition content. You could have a senario where a client his the CE in a proxy configuration where no wccp is used and grab prepostioned content. You are correct in the sense that wccp is simply an intercept senario which then sends the port 80 or 8080 type request to a content engine.