
18
Chapter 3
Web Proxy Caching
•
Background retries
Failed servers are retried in the background and are used (restored to their specified priority) when they
become available.
Several servers supplying different groups
Several news servers can be configured with news servers supplying different (disjoint) groups.
Administrators can use this feature to spread the load based on group.
NNTP cache hierarchies
Using a Traffic Server as parent to a group of Traffic Servers can reduce load on a parent news server and take
advantage of the large number of concurrent connections Traffic Server supports.
Figure 3-4. Hierarchy of news caching servers
In Figure 3-4. above, the parent news server for each of the child Traffic Servers is the parent Traffic Server.
The parent Traffic Server is a child cache to the distant parent news server.
Nonstandard ports and network interfaces
You can configure the interface from which to connect to a parent news server port. You can also configure
the port on the parent server to which Traffic Server connects.
Blocking particular groups
You can block particular groups on specified news servers. Clients do not see blocked groups in news server
group lists. You list all blocked groups in the
nntp_servers.config
file; see page 177.
Clustering
Articles, overview lists, group lists, and LIST files are all maintained in HP’s high performance object store.
This information is updated at configurable intervals so that users and child caches see a consistent view of
news.
Large clusters of Traffic Servers can be configured to act as a single large virtual cache with all the storage
and serving power of the aggregate. See
Chapter 6‚ Traffic Server Clusters
. Article numbers and group
information are maintained consistently across the cluster.
Zurich
Traffic Server Child Caches
London
Traffic Server
Parent Cache
Parent
NNTP
Server
Bombay
Paris
Madrid
Oslo