SDP Capability Negotiation for Multimedia Session Flexibility
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Solution Overview
Problem
Current Session Description Protocol (SDP) lacks the capability to negotiate alternative transport protocols, media types, and media formats without committing to their simultaneous use, and does not support negotiation of unicast and multicast addresses, limiting flexibility in multimedia session establishment.
Innovation Solution
Extension of SDP to include new attributes such as 'a=pcfg' for listing potential configurations, 'a=ctrpr' for transport protocols, 'a=ctrad' for transport addresses, and 'a=capar' for attribute capabilities, allowing endpoints to disclose and negotiate compatible configurations during session initiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If SDP is used to provide fixed media stream descriptions for session announcements, then session initialization is simplified, but flexibility in negotiating alternative configurations is lost
Solution Approach 1:
The patent transforms SDP from a static description format to a dynamic negotiation mechanism by introducing alternative configuration lists and selection indicators. Entities can now propose multiple potential configurations and indicate preferences, allowing the session description to adapt based on participant capabilities rather than being fixed in advance.
Solution Approach 2:
The patent modifies SDP parameters by adding new attributes that enable configuration negotiation. These include lists of alternative transport protocols, media types, and formats, along with selection indicators that allow dynamic parameter selection during session establishment rather than committing to fixed parameters.
2Measurement precision
If SDP commits to specific transport protocols and media formats, then session description is precise, but ability to negotiate alternatives is limited
Solution Approach 1:
The patent segments the session description into mandatory core parameters (for precise description) and optional alternative parameters (for negotiation). By dividing the configuration into essential elements that must be specified and alternative elements that can be negotiated, the patent maintains precision where needed while enabling flexibility where appropriate.
Solution Approach 2:
The patent makes SDP multi-functional by enabling it to serve both as a precise session description format and as a negotiation mechanism. The same SDP structure can convey fixed requirements while also proposing alternatives, allowing a single protocol to fulfill multiple functions without requiring separate mechanisms.
3Adaptability or versatility
If SDP supports multiple media formats simultaneously, then comprehensive capability is achieved, but complexity of negotiation increases
Solution Approach 1:
The patent introduces a feedback mechanism where entities indicate their preferred configuration from the available alternatives. This feedback loop allows the negotiation process to converge on a suitable configuration by considering both offered alternatives and participant preferences, reducing the complexity of evaluating all possible combinations.
Solution Approach 2:
The patent performs preliminary action by having entities pre-identify and list their alternative configurations and preferences before the actual negotiation occurs. By preparing alternative configurations in advance and indicating preferences upfront, the negotiation process becomes more efficient as participants can make informed decisions without evaluating all possibilities from scratch.
Data Source
AI summary
In an example embodiment a method is provided which comprises initiating at an offerer endpoint an offer message in Session Description Protocol (SDP) format. Included in the offer message is an indication of a plurality of potential configurations which the offerer endpoint is capable of supporting. The offer message is sent to an answerer endpoint to allow capability negotiation between the offerer endpoint and the answerer endpoint in a manner that is backwards compatible with existing endpoints. In an example embodiment, the indication of the plurality of potential configurations comprises assigning a new attribute or value to an existing type of SDP identifier.