Method to determine media paths in a SIP network using information from endpoints and intermediate devices
An internet telephony call analyzer receives call information from endpoint and intermediate network devices, corrects timestamp errors in the records, stores the records, and identifies records associated with a single call session between two endpoint devices in the network. The timestamp errors may be corrected by applying a time differential correction to a call start timestamp and call stop timestamp of the record if the timestamp in the record differs from a system timestamp when the record was received by the call analyzer. Call information records associated with the same call session may be matched by identifying records with the same SIP call ID, the same SSRC ID and call start timestamps within a predetermined time interval of each other.
1. A method for determining a network path for an internet telephony call, the method comprising:
receiving by a call analyzer via internet protocol multiple call information records from multiple endpoint and intermediate devices in a network; wherein each of the call information records comprises a call timestamp, an SIP Call-ID value from an SIP header, and an SSRC identifier from an RTP packet header
correcting by the call analyzer timestamp errors in the received multiple call information records;
storing by the call analyzer the received call information records;
identifying by the call analyzer a set of matching call information records from among the multiple call information records using corrected timestamp information in the multiple call information records, wherein the set of matching call information records are associated with a single call session between two endpoint devices in the network, whereby the network path for the single call is determined.
2. The method of claim 1 wherein correcting timestamp errors in the received multiple call information records comprises comparing a timestamp in a record of the multiple call information records with a system timestamp of the call analyzer when the record was received by the call analyzer, and, if the timestamp in the record differs from the system timestamp, applying a time differential correction to a call start timestamp and call stop timestamp of the record.
3. The method of claim 1 wherein identifying the set of matching call information records comprises using SIP call ID information in the multiple call information records, SSRC ID information in the multiple call information records, and timestamp information in the multiple call information records to identify matching records associated with the single call session.
4. The method of claim 1 wherein identifying the set of matching call information records comprises identifying records with a same SIP call ID, a same SSRC ID and call start timestamps within 300 seconds of each other.