The IM2000 Recipient Notification Agent Submission Protocol

The Recipient Notification Agent Submission Protocol is the means by which message stores communicate with recipient notification agents. It shares a common structure and common transport layer requirements with the other IM2000 protocols.

Individual to RNASP are:

• The PDU definitions
• The security considerations
• The individual transactions

With RNASP, the client is the message store, and the server is the recipient notification agent.

PDU definitions

RNASP is subject to the common IM2000 PDU rules.

The response that an RNASP server must send to a client in the event of a parsing error or a non-command PDU is a ResponseNull PDU comprising

• an ErrorMalformedPDU status and
• the forceabort flag set to TRUE.

The response that an RNASP server must send to a client in the event of a timeout is a ResponseNull PDU comprising

• an ErrorCommandTimeout status and
• the forceabort flag set to TRUE.

This is the ASN.1 definition of RNASP.

Security considerations

RNASP is designed for one basic security model with respect to the communications path.

Security with an untrusted communications path

The communications path between client and server may involve third parties. This will usually be the case, since the message store will have no direct prior relationship with the recipient notification agent.

In this case, the protocol is vulnerable to man-in-the-middle attacks, or to any third party capable of injecting traffic into the session. Therefore, for security, clients and servers in such situations should employ transport-level security measures to encrypt PDUs.

Transactions

There is one task which an originator MUA can perform using RNASP, which comprises a single transaction:

• A message store can submit one or more notifications.

Submitting a notification

Submission transactions comprise a single command/response pair. The client sends a CommandNotify PDU containing zero or more notifications, and the server sends a ResponseNotify PDU that (if it does not abort the transaction and does not indicate an error status) indicates that the notifications have been receieved by the server.

Each message notification comprises:

• the location of the message store's MSRAP service from whence the message can be retrieved;
• the recipient mailbox to which this notification applies;
• the message identifier to use for retrieving the message;
• the (publically visible) name of the originator of the message;
• the size (advisory only) of the message, in octets.