> From: ian@mirror-image.com (Ian Cooper)
> To: wrec@cs.utk.edu
> Subject: Re: Taxonomy draft, draft-melve-wrec-taxonomy-00.txt
> Date: Thu, 24 Jun 1999 16:02:55 GMT
>
...
> 2. Terminology
>
> proxy
> An intermediary system which acts as both a server and a
> client for the purpose of making requests on behalf of
> other clients. Requests are serviced internally or by
> passing them on, with possible translation, to other
> servers. A proxy MUST implement both the client and server
> requirements of this specification. A "transparent proxy"
> is a proxy that does not modify the request or response
> beyond what is required for proxy authentication and
> identification. A "non-transparent proxy" is a proxy that
> modifies the request or response in order to provide some
> added service to the user agent, such as group annotation
> services, media type transformation, protocol reduction,
> or anonymity filtering. Except where either transparent or
> non-transparent behavior is explicitly stated, the HTTP
> proxy requirements apply to both types of proxies.
>
> [Ed note: This is also subtly different from HTTP/1.1]
Implementing both server and client requirements is required
only for non-transparent proxies. The notion of a client or
server exists only at certain levels - app, transport, etc.
> tunnel
> An intermediary system which is acting as a blind relay
> between two connections. Once active, a tunnel is not
> considered a party to the HTTP communication, though the
> tunnel may have been initiated by an HTTP request. The
> tunnel ceases to exist when both ends of the relayed
> connections are closed.
Do you want to distinguish or mention types of tunnels? At
first, I thought you meant application tunnels; at second read
this could apply to transport, network, or link tunnels too.
> cache
> A program's local store of response messages and the
> subsystem that controls its message storage, retrieval, and
> deletion. A cache stores cacheable responses in order to
> reduce the response time and network bandwidth consumption
> on future, equivalent requests.
Also to reduce server load.
> ....Any client or server may
> include a cache, though a cache cannot be used by a server
> while it is acting as a tunnel.
This is confusing - it appears to intend to exclude caching as part
of tunneling for a particular transaction; it could be interpreted
as "proxy caches are not allowed to tunnel traffic", even for
separate requests. Is that also intended?
> To these we add the following:
>
> authoritative reference
> the logical owner of data, possibly an origin server
Logical is confusing; as opposed to legal, physical, etc?
why not just say "owner"?
> origin server accelerator
> a reverse proxy with a cache, acting as server to clients,
> and a client to servers.
What is reverse about it? All proxies act as servers to clients; clients
to servers. Does this mean "caches requests", vs a proxy cache "caches
responses" ?
> network element
> router or switch
Or link (e.g., satellite link)? Do you mean "controllable component
of the network", i.e. to exclude hubs?
> server cluster
> a tightly coupled set of servers acting together to share
> load
> [Ed note: was proxy cluster - makes more sense to have a
> generic term]
Wouldn't the generic term be "cluster, as in proxy cluster or server cluster"?
> reverse proxy
> An intermediary system which acts as both a server and a
> client for the purpose of serving requests on behalf of
> origin servers. Requests are serviced internally or by
> passing them on to the origin server they are representing.
> A reverse proxy must interpret and, if necessary, rewrite a
> request message before forwarding it. Reverse proxies are
> often used as server-side portals through network firewalls
> and as helper applications for off loading requests from
> origin servers.
This definition isn't sufficiently different from "proxy cache" -
what's reverse about it?
>
>
> The following definitions are added to describe caching device
> topology:
>
>
> user agent cache
> the cache within the user agent program
>
> local caching proxy
> the caching proxy a user agent connects to
local is a relative term; a server can have a local caching proxy too
(an accelerator). If this is the user's first proxy, can we call
this "client caching proxy"? or Primary proxy?
> upper level caching proxy
> seen from the content consumer's view, all caches
> participating in the caching mesh that are not the user
> agent's local caching proxy
Secondary or intermediate proxy? (upper-level has many implications:
- that the proxy topology is necessarily hierarchical (it is not)
- upper means closer to the server
it could mean HTTP-layer, vs. TCP-layer
> central cache server
> a centralized server to requests made by local and upper
> level caching proxies, but which does not act as a proxy
this can be called just a "cache server" - whether it is central
or not is independent.
> cache cluster
> a server cluster whose cache is shared between the
> individual servers
Then call it a server cluster with central cache.
A cache cluster implies a cluster of caches - any cluster, including
a cluster of proxies.
> diffused arrays
> tightly coupled array of caching proxy servers, acting
> logically as one service and partitioning the URL name
> space across the array
> [Ed note: looks like the above two terms should be merged
> in some way.]
this is a cache cluster. how requests are 'routed' or dispensed
within the cluster is the business of the cluster, and not
a term that needs defining.
> caching mesh
> a loosely coupled set of co-operating proxy- or caching-
> servers, or clusters, acting independently but sharing
> cacheable content between themselves using inter-cache
> communication protocols (see Section 7)
this too is a cache cluster.
cache clusters have properties:
request 'routing'
object partitioning
Some of these are being defined in the research issues document too.
I'll post an update of that later today.
> network traffic interception
> the examination of network traffic within a network
> element to determine whether it should be redirected
> [Ed note: still needs some work - doesn't fully consider
> an environment where the proxy is in a bridge]
Intercept implies to capture that traffic, not just examine it.
Snooping matches the definition better.
> transparent proxy (additional definition)
> the term "transparent proxy" is defined in [6] (and quoted
> above). However, in the realm of Web caching, this has
> come to define a proxy which receives traffic as a result
> of network traffic interception. The term typically
> describes the use of a proxy and the additional systems
> which performing network traffic interception. The use of
> the proxy is transparent to the client.
...and possibly to the network as well.
> proxy autodiscovery
> this describes the discovery and configuration for use of
> a proxy in an environment where the content consumer may
> be unaware of the proxy's existence. The use of the proxy
> is transparent to the content consumer, but not to the
> client.
is this exclusive to the client? don't/couldn't proxies also autodiscover
each other too?
> temporal domain, sparse working set cache
> a subset of the content from one or more origin servers,
> stored temporarily and collected from requests made by
> content consumers
the use of the term domain may be overloaded (DNS domain).
the use of the term temporal is redundent with the term cache.
I'm not sure why such a specific term is required, either.
> persistent domain
> a collection of origin servers maintaining a persistent
> data set from the authoritative reference
the use of the term domain may be overloaded. do you require
that the server set be in the same DNS domain?
> replica origin server
> origin server storing a persistent replica of a data set
> stored at the authoritative reference
Joe
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