Do I really need reliable sessions for my services? (description inside)

Question

Our company leases a music service to it's clients. The product consists of an automated mp3 player and daily renewals/updates of the costumers music library (mp3 songs) downloaded to their machines. So far we use an ugly solution for the mp3 updates, by synchronizing server and client folders using GBridge. This is obviously a disadvantage, as we force our clients to download our whole music library (currently 25.000 songs) while most of them will never play songs from all of our music categories (pop, rock etc). Most important we can only offer one subscription packet (our whole music library) while our competitors offer packets by categories with lower prices. For those reasons we decided to turn to WCF.

The service uses PerCall instancing mode and implements two operations, invoked from a winform client application with the classic request-reply pattern.

The first operation retrieves from a database the categories a client is allowed to download from (request) and sends back to the client a list of these categories (reply).

The second operation is used for downloading. The client first downloads an xml version of the server's database. A similar xml lies on the client side. The client app checks which songs, in each of the categories returned from the first operation, are missing in it's own xml compared to the server's xml file. If there are any files (elements on the xml) missing, it downloads them one file at a time. After each download, the client updates his xml and does the same comparison again until all files (elements) match in the 2 xml.

Long story short, considering that the instancing mode on the service is PerCall for throughput reasons and keeping memory consumption low and that both my operations use the request-reply pattern which means that the acknowledgement messages will be send back to the client with each response from the service, so if something goes wrong in the connection or if the client can't reach the service I can catch the CommunicationObjectFaultedException on the client, reconstruct the proxy and retry do you think theres a need for reliable sessions on my service implementation? What problems could arise if I don't have reliable sessions in the operations just described?

Answer 1

What problems could arise if I don't have reliable sessions in the operations just described?

I am aware of only few problems being solved by reliable sessions while it puts a lot of stress on the server.

I would personally go for BasicHttpBinding (for better interoperability) without reliable session.

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UPDATE

In order to understand Reliable Sessions, have a read of this and this.

If you are a bank, it makes sense to use Reliable Sessions, if you are sending money to and from other banks. This will ensure the message is received by the final party involved. But in most cases, you would not need it.