METHODS AND APPARATUS FOR PREVENTING HEAD OF LINE BLOCKING FOR RTP OVER TCP

• US 20160380901A1
• Filed: 09/12/2016
• Published: 12/29/2016
• Est. Priority Date: 03/03/2014
• Status: Active Grant

• Current Assignee: Ribbon Communications Operating Company, Inc. (Ribbon Communications, Inc.)
• Original Assignee: Sonus Networks Incorporated (Ribbon Communications, Inc.)
• Inventors: Asveren, Tolga
• Granted Patent: US 10,129,163 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H04L 47/193 at the transport layer, e.g. TCP related
• CPC Class Codes: H04L 47/22 Traffic shaping
• CPC Class Codes: H04L 47/34 ensuring sequence integrity, e.g. using sequence numbers
• CPC Class Codes: H04L 47/6205 Arrangements for avoiding head of line blocking

Abstract

Methods and apparatus for processing and using TCP packets to communicate RTP packets are described. Head of line blocking is avoided by operating a TCP packet processing module to output RTP packet data to an application irrespective of whether or not a preceding TCP packet was received. Since output of packet data to an application using RTP packets is not delayed when there is a missing TCP packet, head of line blocking is avoided. RTP packet data is subjected to pattern matching in order to identify and process RTP packets in the case where RTP header information such as packet length information is missing due to the failure to receive a TCP packet. The methods are particularly well suited for the communication of audio and/or video by devices operating behind firewalls which block UDP or other types of packets other than TCP packets.

Claims

1. A method of communicating packets using TCP, the method comprising:

receiving a TCP packet which is part of a TCP packet sequence;

extracting data from said TCP packet; and

providing said extracted data and a corresponding TCP packet sequence number to an RTP application irrespective of whether or not a preceding TCP packet in said packet sequence has been received.

2. The method of claim 1, further comprising:

adding said extracted data to a sequence of stored packet data at a location in said sequence of stored packet data, said location being a location determined based on the corresponding TCP packet sequence number associated with the extracted data.

3. The method of claim 1, further comprising:

determining if said corresponding TCP packet sequence number is higher than the highest previously received TCP packet sequence number corresponding to said TCP packet sequence; and

when it is determined that the received TCP sequence number is higher than the highest previously received sequence number corresponding to said TCP packet sequence;

incrementing a received TCP sequence counter to set a highest received sequence number of said TCP sequence counter to said corresponding TCP packet sequence number.

4. The method of claim 3, further comprising:

sending an acknowledgement indicating successful receipt of a TCP packet when said received TCP packet causes incrementing of said received TCP sequence counter.

5. The method of claim 3, further comprising:

receiving a second TCP packet which is part of said TCP packet sequence;

extracting second data from said second TCP packet; and

providing said extracted second data and a corresponding second TCP packet sequence number to the RTP application irrespective of whether or not a preceding TCP packet in said packet sequence has been received.

6. The method of claim 5, further comprising:

adding said extracted second data to the sequence of stored packet data at a location in said sequence of stored packet data, said location being a location determined based on a second TCP packet number associated with the extracted second data.

7. The method of claim 6, further comprising:

processing data in said sequence of packet data to identify RTP packet boundaries.

8. The method of claim 7, wherein said step of processing data in said sequence of packet data to identify RTP packet boundaries includes:

performing a pattern matching operation to identify at least one RTP header field within said data; and

determining a location of a RTP packet boundary based on the location of the identified header field in said data and a known offset from the location of said header field to the start of an RTP packet which includes the at least one identified RTP header field.

9. The method of claim 8, wherein performing a pattern matching operation includes checking the data for expected patterns matching at least two of the following RTP header fields:

a version field, a payload type field, a sequence number field, a timestamp field, and an SSRC field.

10. The method of claim 8, further comprising:

identifying a length field immediately preceding the start of an RTP packet header including the at least one identified RTP header field;

determining RTP packet length based on information included in the identified length field; and

determining the end of the RTP packet including the identified at least one RTP header field based on the determined RTP packet length.

11. An apparatus for communicating packets using TCP, comprising:

memory; and

a processor configured to control said apparatus to;

receive a TCP packet which is part of a TCP packet sequence;

extract data from said TCP packet; and

provide said extracted data and a corresponding TCP packet sequence number to an RTP application irrespective of whether or not a preceding TCP packet in said packet sequence has been received.

12. An apparatus for communicating packets using TCP, comprising:

an interface including a receiver configured to receive a TCP packet which is part of a TCP packet sequence;

a data extraction module configured to extract data from said TCP packet; and

a communications module configured to provide said extracted data and a corresponding TCP packet sequence number to an RTP application irrespective of whether or not a preceding TCP packet in said packet sequence has been received.

13. The apparatus of claim 12, further comprising:

a memory including a sequence of stored packet data.

a modification module configured to add said extracted data to said sequence of stored packet data at a location in said sequence of stored packet data determined based on the corresponding TCP packet sequence number associated with the extracted data.

14. The apparatus of claim 12, further comprising:

a determination module configured to determine if said corresponding TCP packet sequence number is higher than the highest previously received TCP packet sequence number corresponding to said TCP packet sequence; and

a sequence counter control module configured to increment a received TCP sequence counter to set a highest received sequence number of said TCP sequence counter to said corresponding TCP packet sequence number, when said determination module determines that the received TCP sequence number is higher than the highest previously received sequence number corresponding to said TCP packet sequence.

15. The apparatus of claim 14, further comprising:

an acknowledgement communications control module configured to send an acknowledgement indicating successful receipt of a TCP packet when said received TCP packet causes incrementing of said received TCP sequence counter.

16. The apparatus of claim 14,

wherein said receiver is further configured to receive a second TCP packet which is part of said TCP packet sequence;

wherein said data extraction module is further configured to extract second data from said second TCP packet; and

wherein said communications module is further configured to provide said extracted second data and a corresponding second TCP packet sequence number to the RTP application irrespective of whether or not a preceding TCP packet in said packet sequence has been received.

17. The apparatus of claim 16,

wherein said modification module is further configured to add said extracted second data to the sequence of stored packet data at a location in said sequence of stored packet data determined based on a second TCP packet sequence number associated with the extracted second data.

18. The apparatus of claim 17, further comprising:

a processing module configured to process data in said sequence of packet data to identify RTP packet boundaries.

19. The apparatus of claim 18, wherein said processing module is further configured, as part of being configured to process data in said sequence of packet data to identify RTP packet boundaries, to perform the following:

perform a pattern matching operation to identify at least one RTP header field within said data; and

determine a location of a RTP packet boundary based on the location of the identified header field in said data and a known offset from the location of said header field to the start of an RTP packet which includes the at least one identified RTP header field.

20. The method of claim 19, wherein performing a pattern matching operation includes checking the data for expected patterns matching at least two of the following RTP header fields:

a version field, a payload type field, a sequence number field, a timestamp field, and an SSRC field.