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3.1.1.2 Sequence Numbers

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All Coded Packets and Source Packets have a sequence number that identifies their sending order. The sequence numbers for the Coded Packets and the Source Packets are independent of each other.

The Initial Sequence Number abstract data model (ADM) element for both Coded Packets and Source Packets is initialized as follows:

Initial Sequence Number = snInitialSequenceNumber in the RDPUDP_SYNDATA_PAYLOAD Structure (section 2.2.2.5).

This initial value is a true random number. This field is similar to the initial sequence number (ISN) field used in the TCP transport protocol; for more information about the ISN field, see [RFC1948].

The Coded Packet sequence number is referred to as the Coded sequence number. The Coded sequence number uniquely identifies each datagram sent by the sender. The Coded sequence number value is increased by one for each Coded Packet that was sent. Retransmitted Source Packets can have different Coded sequence numbers.

The Source Packet sequence number is referred to as the Source sequence number. Each Source Packet encapsulates a data payload. The Source sequence number uniquely identifies this data payload. The Source sequence number value is increased by one for each data payload that was sent.

The sequence numbers wrap around due to space limitations. Implementations MUST handle this wrap-around scenario. For more information about the sequence numbers range, see [RFC793] section 3.3.