Performance enhancing proxy techniques for internet protocol traffic

• US 20030131079A1
• Filed: 11/13/2002
• Published: 07/10/2003
• Est. Priority Date: 11/13/2001
• Status: Abandoned Application

• Current Assignee: Advantech Satellite Networks Inc.
• Original Assignee: EMS Technologies, Inc. (Honeywell International Inc.)
• Inventors: Neale, Jason, Begin, Guy, Mohsen, Abdul-Kader, Pether, Andrew M.
• Application Number:
  US10/292,899
• Publication Number:
  US 20030131079A1
• Time in Patent Office: Days
• US Class Current: 709/220
• CPC Class Codes: H04B 7/18582 Arrangements for data linking, i.e. for data framing, for error recovery, for multiple access
• CPC Class Codes: H04L 1/18 Automatic repetition systems, e.g. Van Duuren systems
• CPC Class Codes: H04L 1/1832 Details of sliding window management
• CPC Class Codes: H04L 1/1848 Time-out mechanisms
• CPC Class Codes: H04L 12/2856 Access arrangements, e.g. Internet access asynchronous transfer mode networks H04L12/5601; broadband local area networks H04L12/2801; optical access or distribution networks H04Q11/0067; access to open networks H04L12/5691; digital subscriber line end-user equipment and bit-level processing of data on a PSTN-based network H04M11/00; home network gateways H04L12/2834; wireless access networks H04W
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/193 at the transport layer, e.g. TCP related
• CPC Class Codes: H04L 47/29 using a combination of thresholds
• CPC Class Codes: H04L 47/30 in combination with information about buffer occupancy at either end or at transit nodes
• CPC Class Codes: H04L 47/323 Discarding or blocking control packets, e.g. ACK packets
• CPC Class Codes: H04L 47/36 by determining packet size, e.g. maximum transfer unit [MTU]
• CPC Class Codes: H04L 67/04 specially adapted for terminals or networks with limited capabilities; specially adapted for terminal portability
• CPC Class Codes: H04L 69/16 Implementation or adaptation of Internet protocol [IP], of transmission control protocol [TCP] or of user datagram protocol [UDP]
• CPC Class Codes: H04L 69/161 Implementation details of TCP/IP or UDP/IP stack architecture; Specification of modified or new header fields
• CPC Class Codes: H04L 69/163 In-band adaptation of TCP data exchange; In-band control procedures
• CPC Class Codes: H04L 69/165 Combined use of TCP and UDP protocols; selection criteria therefor
• CPC Class Codes: H04L 69/166 IP fragmentation; TCP segmentation
• CPC Class Codes: H04L 69/326 in the transport layer [OSI layer 4] H04L69/16 takes precedence
• CPC Class Codes: H04L 69/329 in the application layer [OSI layer 7]
• CPC Class Codes: H04L 9/40 Network security protocols
• CPC Class Codes: H04W 28/0273 : adapting protocols for flow control or congestion control to wireless environment, e.g. adapting transmission control protocol [TCP] wireless network protocols or protocol adaptations to wireless operation, e.g. wireless application protocol H04W80/00
• CPC Class Codes: H04W 72/0453 : Resources in frequency domain, e.g. a carrier in FDMA
• CPC Class Codes: H04W 8/04 : Registration at HLR or HSS [Home Subscriber Server]
• CPC Class Codes: H04W 80/06 : Transport layer protocols, e.g. TCP [Transport Control Protocol] over wireless transmission control protocol/Internet protocol [TCP/IP] or user datagram protocol [UDP] H04L69/16
• CPC Class Codes: H04W 84/06 : Airborne or Satellite Networks space-based or airborne stations H04B7/185

Abstract

Methods and systems are described that may be used in the context of a Performance Enhancing Proxy architecture for Internet traffic. A method of accelerated connection opening with error handling is disclosed. Also, a method of handling the Path MTU Discovery mechanism in the context of a distributed connection splitting PEP is described. A novel packet format for a proprietary inter-PEP protocol is described which allows for low packet header overhead. A new acknowledgement scheme that adapts to packet loss conditions to minimize bandwidth consumption by selecting an acknowledgement type from several possibilities is also detailed. A method whereby potentially spurious retransmissions are minimized by timing every transmission and retransmission is also described.

Claims

1. A method for accelerating an opening of a connection in a communications system for transmitting and receiving data packets, the method comprising the steps of:

intercepting a TCP SYN connection request from a client, the TCP SYN intercepted by a first Performance Enhancing Proxy (PEP);

responding to the intercepted TCP SYN connection with a TCP SYN/ACK, the step of responding performed by the client;

responding to the first PEP with the TCP ACK, the responding step performed by the client;

converting the TCP SYN to another protocol and sending a message over a link, the converting and sending steps performed by the first PEP;

receiving the message over a link and converting it back to the TCP SYN, the receiving and converting steps performed by the second PEP;

sending the TCP SYN to a server, the sending step perfomed by the second PEP; and

listening for ICMP messages generated in response to the TCP SYN, the listening step performed by the second server.

2. The method of claim 1, further comprising the steps of:

receiving the ICMP message related to a connection that is currently being established, the receiving step performed by the second PEP;

removing said ICMP message from the network;

generating a reset message;

forwarding the reset message to the first PEP; and

forwarding the reset message to the client, the forwarding step performed by the first PEP.

3. The method of claim 1, further comprising the steps of:

receiving an ICMP message related to a connection that is currently being established, the ICMP message received by the second PEP;

forwarding the ICMP message to the first PEP; and

forwarding the ICMP message to said client, the ICMP message forwarded by the first PEP.

4. The method of claim 3, further comprising the steps of:

generating a reset packet and sending it over the link to the first PEP, the generating and sending steps performed by the second PEP; and

forwarding the reset message upon returning the ICMP message to the client, the forwarding step performed by the first PEP.

5. The method of claim 3, further comprising the steps of:

generating a reset message upon receiving the ICMP message, the generating step performed by the first PEP; and

sending the reset message to the client after the forwarding of the ICMP message, the sending step performed by the first PEP.

6. A method of supporting an end-to-end PMTUD mechanism in a communications system for transmitting and receiving data packets, comprising the steps of:

identifying messages to intercept via a destination IP address and an encapsulated packet fragment;

intercepting incoming ICMP “

Fragmentation Needed, DF Set”

messages from a TCP end connection;

re-sizing a path MTU estimate for an indicated destination IP address at a PEP to a value indicated by the ICMP messages or if no value is indicated to a default of 576 bytes; and

re-packetizing an original packet according to a newly set path MTU estimate; and

re-transmitting from PEP previously discarded data.

7. The method of claim 6, wherein the step of re-packetizing further comprises:

dividing data of a packet requiring subdivision into path MTU sized portions and a possible remainder of less than path MTU bytes;

creating a new set of TCP headers for subdivisions of the original packet that preserve TCP connection information contained in the original packet; and

creating a new set of IP headers for the subdivisions of the original packet that preserve the IP information contained in the original packet.

8. The method of claim 6, wherein the step of re-packetizing futher comprises:

treating the data as a byte stream; and

combining portions of multiple large packets into smaller packets.

9. A packet header for transmitting and receiving data packets in a communications system for transmitting and receiving data packets, comprising:

a first field containing a source port number;

a second field containing a destination port number;

a third field comprising 8 individual bit flags;

a forth field containing a packet number;

a fifth flag field;

a sixth field including either 0 or more individual bit flags;

a seventh, field containing an acknowledgement number;

an eighth field containing the header length in units of 4 bytes;

a ninth reserved field;

a tenth flag field;

an eleventh flag field;

a twelfth flag field;

a thirteenth flag field;

a fourteenth flag field;

a fifteenth flag field;

a sixteenth field containing an advertised window size;

a seventeenth checksum field; and

an eighteenth field containing an urgent pointer.

10. The packet header in accordance with claim 9, wherein the fourth header field is no greater than 31 bits and the seventh header field is no greater than 31 bits.

11. The packet header in accordance with claim 9, wherein the fourth field is utilized as 24 1-bit flags for acknowledging individual packets.

12. A method for use in a communications system for sending and receiving data packets for acknowledging a plurality of data packets to automatically reduce the number of acknowledgement packets under differing link conditions, the method comprising the steps of:

constructing an acknowledgement packet having a first format;

updating the acknowledgement packet as the packets are considered at least one of received or missing;

converting the acknowledgement packet to an alternative format in order to minimize the packets required to be sent; and

sending the packet when it is full.

13. The method of claim 12, further comprising the step of using a timer to limit a maximum delay between the acknowledgement packets.

14. A method for maintaining information on transmitted packets in a communications system for sending and receiving data packets, the method comprising the steps of:

transmitting a packet;

locally storing a timestamp representing a time of transmission of the packet;

determining a packet loss; and

determining if a retransmission may take place based upon the determined packet loss.

15. The method of claim 14, wherein the timestamp represents an expected time of reception of a confirmation of a successful receipt.

16. The method of claim 14, wherein the step of determining a packet loss entails a failure to receive an acknowledgment as indicated by the expiration of a timer or receipt of a negative acknowledgement or an acknowledgement for a later packet.

17. The method of claim 14, further comprising the step of determining which packet to retransmit.

18. The method of claim 17, wherein the step of determining which packet to retransmit further includes the step of finding all packets where a packet number is less than the packet determined missing and a time stamp indicates that an acknowledgement should have been received.