The wheel has been reinvented several times in signaling protocols. Most signaling protocols re-invent, e.g., their own signaling transport methods, end-point discovery, measures for reliable exchange of messages and security features. Next Steps In Signaling (NSIS) framework was created in the IETF to design a single unified framework for various network signaling needs. The signaling transport layer of NSIS, the General Internet Signaling Transport (GIST), was specified in the IETF to provide a common transport service for signaling applications. The NSIS suite also includes two signaling protocols, NSIS Signaling Layer Protocols (NSLP), one for Quality of Service provisioning and one to configure middleboxes, in particular Network Address Translators and firewalls.
The different signaling applications use GIST message delivery services through an API that consists of several operations. On top of common operations for sending and receiving data, the API also covers network events, errors and session state management. The API covers all GIST aspects, and allows application developers to have adequate knowledge of network state. However, as a result the API is very cumbersome to use, and an application developer needs to take care of non-trivial amount of details. A further challenge is that to create a new signaling application, one needs to acquire and register a unique NSLP identifier with the Internet Assigned Numbers Authority (IANA).
This thesis presents the Messaging NSLP, that provides an abstraction layer to hide complex GIST features from the signaling application. Developers of Messaging Applications can use a simple Messaging API to open and close sessions and to transfer application data from one Messaging Application node to another.
Prototype implementations of NSLP API and Messaging NSLP were created and tested to verify the protocol operation with various network scenarios. Overhead analysis of GIST and Messaging NSLP were performed, and results are compatible with earlier, third-party analysis. The Messaging NSLP can introduce up to 938 bytes of overhead to initiate a signaling session, but later signaling only introduces 78 bytes of header overhead.
