Multicast Server SSRC Conflict Resolution
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Solution Overview
Problem
In multicast broadcasting, clients cannot determine the IP addresses of other sources within the same group without subscribing to their streams, leading to potential SSRC identifier conflicts that degrade the quality of service.
Innovation Solution
A method where a multicast server distributes source identifiers by maintaining a table of {source identifier; source address} pairs, allowing clients to receive arrival and departure announcements without subscribing to other sources, and communicates these pairs to all sources in the group, enabling unique identifier assignment and conflict prevention.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of information
If clients subscribe to other sources to obtain their IP addresses, then clients can determine source addresses, but clients cannot avoid SSRC identifier conflicts and service quality degradation
Solution Approach 1:
The patent introduces a multicast server as an intermediary that maintains a mapping table between SSRC identifiers and source IP addresses. Clients subscribe only to the server to obtain this mapping information, eliminating the need to subscribe to other sources while avoiding identifier conflicts. The server mediates between clients and other sources by providing address resolution services.
2Device complexity
If clients do not subscribe to other sources, then clients avoid unnecessary subscriptions, but clients cannot obtain source IP addresses and detect identifier conflicts
Solution Approach 1:
The multicast server acts as an intermediary that centralizes the storage and distribution of SSRC-to-IP-address mappings. Clients interact only with the server to obtain identifier information, simplifying subscription management while ensuring access to complete source identifier data through the server's mapping table.
3Loss of information
If the server forwards announcement messages to the multicast group address, then clients receive identifier information, but clients may incorrectly modify their identifiers due to receiving their own SSRC
Solution Approach 1:
The patent extracts the SSRC identifier information from the public multicast group channel and delivers it privately to each client through unicast communication from the server. The server retrieves the client's SSRC from its mapping table and sends it directly to the client, preventing the client from receiving its own identifier through the multicast group and avoiding incorrect modifications.
4Ease of operation
If multiple clients use the same SSRC identifier, then identifier assignment is simplified, but multicast broadcasting quality degrades due to conflicts
Solution Approach 1:
The server provides feedback to clients about SSRC identifier availability by maintaining a mapping table that tracks which identifiers are currently in use. When a client joins, the server checks its table and informs the client whether its chosen SSRC is unique or already taken, allowing the client to select an alternative identifier if necessary, thus preventing conflicts while keeping the assignment process simple.
Data Source
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Figure 2
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AI summary
The invention relates to a method for distributing identifiers of sources from a multicast group (G), said sources being interconnected via an electronic communications network (301), the multicast group being identified by a group address (a G), a stream transmitted to the group address by a first source being received by a second source if the second source is already subscribed to the first source, one of the sources, known as the server (101), being subscribed to all of the other sources (201, 202, 20x). The method comprises the following steps performed by the server: reception from one of said other sources, known as the announcement source (201, 202), of a multicast announcement message comprising an announcement source identifier; and transmission of a management message to the group address, comprising the announcement source identifier.