Solution Strategies

 

The previous sections have shown drawbacks of the provision of local newsgroups and provision of Usenet News to areas with limited network bandwidth. The following sections will give an overview of possible solution strategies for these drawbacks. Among these solutions we will present our News Cache and will explain the benefits of this approach briefly. The News Cache itself will be discussed in the following chapters in detail.

Server-Multiplexing by the Client

  This demand can be solved by patching all existing news readers. Unfortunately it is obvious that this is impossible. However, this would be the cleanest approach, because the client would decide which server to contact for which newsgroup without requirements for additional software. A possible solution is to keep a configuration file for each news server and to reconfigure the news reader for each session. Figure 3.6 shows a possible workaround for news readers storing their configuration in ~/.newsrc. This workaround works for most Unix and Unix-like systems. Similar workarounds exist for other news readers and other environments.

  

Abbildung 3.6: Workaround to multiplex between different news servers

Server-Multiplexing by the News Cache

  The workaround presented in section 3.4.1 does not work for all news servers and is inconvenient to the user in several ways. On the one hand if the user wants to read a newsgroup from another server, he has to terminate the news reader and restart it. On the other hand the presented workaround reduces the functionality of some news reader to work on several newsgroups simultaneously. This functionality will not be available for newsgroups stored on different news servers.

The News Cache can include the functionality to contact different news servers for different newsgroups. Whenever a news reader selects a newsgroup from the News Cache, the News Cache decides which news server to contact for the given newsgroup. All this will be done transparently to the news reader. Another advantage of this approach is that the user needs not to worry about which newsgroups are provided by which news server.

News on Networks with Limited Bandwidth

  This problem can only be solved for leaf node news servers without modifications to NNTP. Since leaf node news servers need not hold the whole news feed, they can be replaced by a News Cache. The News Cache retrieves only those articles that are requested by a news client. Thus the News Cache eliminates the transmission of articles that will never be accessed by any news client.

To solve this problem in general it is necessary to add some new commands to NNTP. One command could be a request to transfer the articles in compressed form. This could reduce the required network bandwidth by approximately $50\%$. Another command could request the transfer of all newly arrived articles smaller than a given size. This is useful, because it does not pay to negotiate the transmission of small articles and the transmission of larger articles (e.g. those found in the binary newsgroups) will be negotiated. An explanation of the currently used article negotiations can be found in [KL86].