Recipe8.21.Configuring NNTP for Newsgroup Feeds

Recipe 8.21. Configuring NNTP for Newsgroup Feeds

Problem

You want to use set up a newsgroup feed and populate the Exchange Internet Newsgroups public folder hierarchy.

Solution

Using a graphical user interface

Open the Exchange System Manager (Exchange System Manager.msc).
In the left pane, expand the appropriate Administrative Groups container and expand the Servers container.
Expand the target server, expand its Protocols object, and the NNTP object.
Double-click the desired NNTP virtual server (usually the default unless you have multiple NNTP virtual servers defined).
Right-click Feeds and select New Feed to launch the New NNTP Feed Wizard.
Select the role that defines the remote server, which will almost always be a Peer server and click Next.
Configure the direction of this feed:
- If this feed will receive incoming articles via a pull feed, select the Inbound feed checkbox and select Pull articles from the remote server.
- If this feed will receive incoming articles via a push feed, select the Inbound feed checkbox and select Accept a push feed from the remote server.
- If this feed will provide outgoing articles to the remote server, select the Outbound feed checkbox.
Click Next.
If you selected an incoming pull feed, select the article date and time from which you wish to begin receiving posted articles; the feed will attempt to receive all posts on the remote server that have timestamps earlier than the selected timestamp. Click Next.
By default, an incoming pull feed will retrieve messages from all newsgroups on the remote server. Modify the list of retrieved newsgroups as follows:
- To only retrieve certain groups, click Remove to remove the default * entry. For each group hierarchy you desire, click Add, select Include, type the name of the hierarchy, and click OK.
- To exclude only certain groups, leave the default * entry. For each group hierarchy you wish not to retrieve, click Add, select Exclude, type the name of the hierarchy, and click OK.
- If this feed is an incoming push feed, leave this setting at default.
When you have completed modifying your desired newsgroups, click Finish.
Open the property sheet for the newly created feed and click the General tab:
- Select the Enable feed checkbox if it is not already checked.
- Ensure that the value of the Unique path ID generated by the remote server field matches the settings provided by your news peer; this is important if they will be feeding you news from multiple machines.
- Ensure that the value of the Outbound port field matches the settings provided by your news peer, usually 119 by default.
Click the Schedule tab and select the desired time interval for retrieving and sending messages via this feed.
If your news peer requires authentication, click the Security tab and input the necessary credentials. You can only use Basic authentication.
Click OK to close the property sheet.
Allow sufficient time for the feed propagation to begin. You should be able to see the new newsgroups in the Newsgroups container in Exchange System Manager.

Discussion

The Exchange 2000 NNTP implementation is a functional (though no-frills) implementation of the NNTP protocol and it hasn't changed appreciably in Exchange Server 2003. You should always gain explicit permission from your news peers before configuring a feed, although many ISPs offer a newsgroups feed as part of a high-bandwidth (T-1 or higher) circuit package.

You should never need to create NNTP feeds to propagate groups within your Exchange organization; the public folder replica and replication mechanism provides finer control and follows your organization's routing group topology. As such, there should usually be one well-defined interface between your Exchange organization and external news feeds. Also be aware that NNTP feeds can only be used for groups under the Internet Newsgroups folder in your default public folder tree; they cannot be used to replicate other public folder hierarchies with foreign systems.

News feeds are asynchronous by default; any articles generated within your organization propagate to external news server through outbound feeds, while all externally originated messages come in through incoming feeds. In addition, incoming feeds have two types:

Pull feeds make use of the NEWNEWS NNTP command; this type of feed may also be called a sucking feed. With this kind of feed, Exchange will attempt to see all the new articles that have arrived on the peer news server since the last connection and retrieve them individually as if it were a news client. In general, ISPs and news peers don't like pull feeds, since they typically use up more than their fair share of bandwidth, memory, and CPU resources. Dedicated newsgroup transit software makes provisions automatically to spool up relevant news messages for their peers, and a pull feed bypasses this optimization. As a result, many providers disable the NEWNEWS command.
Push feeds use the IHAVE/SENDME NNTP commands. In this case, a server that receives a new message (whether from a local poster or from a peer) will announce a new message to its peers, which, in turn, will either ask for the message to be sent or reject it if they already have a local copy of the message. Exchange push feeds do not make use of the NNTP streaming extensions, which make better use of bandwidth for high-volume news feeds by reducing the number of roundtrips required to send each message. Most newsgroup feeds, especially from peers with Unix-based news servers, will use, at minimum, a push feed.

It is not uncommon to configure multiple Exchange news feeds for a peering agreement with a single provider. Many newsgroup providers have large farms of high-speed dedicated news transit servers for redundancy; your organization may need to permit incoming connections from multiple servers (news01, news02, news03, etc.), all of which will use the same Path ID header to prevent replication loops. The corresponding outgoing feed will often go to yet another FQDN, usually a DNS CNAME pointing to multiple servers. When configuring these kinds of peering feeds, be sure to adjust the unique path ID generated by the remote server field on the General tab of the feed property sheet.

Although you can adjust the feed subscription on both push and pull feeds, it is only relevant to pull feeds; push feeds will accept all messages given to them, so be sure the peer has an accurate list of which groups to offer. Group subscriptions can be fully qualified group names (e.g., news.admin.net-abuse.blocklisting) or simple wildcard pattern matches (e.g., news.admin.* provides all of the groups in the news.admin hierarchy).

The interaction between the NNTP flood-fill protocol and public folder flood-fill replication can provide all sorts of potential trouble if you have feeds with multiple external peers. While having multiple peers is a traditional method to ensure faster, more complete Usenet propagation, you should be careful to use the same server to handle all feeds involving a given group to avoid the potential for replication errors and loops. This practice also ensures that you will never have more than one copy of a given message transmitted to your organization, thus saving bandwidth.

Using Exchange directly to exchange newsgroups with external systems may not be the right solution for your organization. A full Usenet feed transmits over 1 TB of data per day, most of which is binary groups, and the use of the NNTP streaming protocol extensions can make a noticeable difference in the speed and quality of newsgroup propagation over WAN links. If you require a full feed, specialized filtering (such as anti-spam or anti-virus checking), efficient use of your WAN bandwidth, or a greater level of redundancy for your newsgroups feeds, then you should probably investigate using specialized NNTP transit software on a dedicated host to handle your newsgroup feeds from the outside world. You can then provide a sanitized feed from this machine to your Exchange organization over your local high-bandwidth network. Additionally, you can investigate the use of the Exchange master/subordinate feed settings, which allow you to establish a group of Exchange servers that loosely work together as a single entity. Since the NNTP service cannot be clustered, this allows greater redundancy for the organization.