Packet fragmentation prevention

• US 20040001444A1
• Filed: 06/26/2002
• Published: 01/01/2004
• Est. Priority Date: 06/26/2002
• Status: Active Grant

• Current Assignee: Avaya Incorporated
• Original Assignee: Avaya Incorporated
• Inventors: Sadot, Emek, Zilbershtein, Itai Ephraim
• Granted Patent: US 9,088,494 B2
• Time in Patent Office: Days
• US Class Current: 370/252
• CPC Class Codes: H04L 47/10 Flow control; Congestion control
• CPC Class Codes: H04L 47/36 by determining packet size, e.g. maximum transfer unit [MTU]
• CPC Class Codes: H04L 47/43 Assembling or disassembling of packets, e.g. segmentation and reassembly [SAR]
• CPC Class Codes: H04L 69/166 IP fragmentation; TCP segmentation

Abstract

A method of avoiding packet fragmentation. The method includes receiving a data packet belonging to a data connection, determining whether the received data packet was fragmented or determining whether the received data packet is expected to be fragmented on the way to its destination and registering the data connection of the received packet in a list of connections that carried packets that were fragmented or were expected to be fragmented.

Claims

1. A method of avoiding packet fragmentation, comprising:

receiving a data packet belonging to a data connection;

determining whether the received data packet was fragmented or determining whether the received data packet is expected to be fragmented on the way to its destination; and

registering the data connection of the received packet in a list of connections that carried packets that were fragmented or were expected to be fragmented.

2. A method according to claim 1, wherein receiving the data packet comprises receiving a packet belonging to a transmission control protocol (TCP) connection.

3. A method according to claim 1, wherein receiving the data packet and registering the connection are performed by an intermediate network element, which is not an end unit of the connection.

4. A method according to claim 3, wherein the intermediate network element comprises a load balancer.

5. A method according to claim 3, wherein the intermediate network element comprises a firewall.

6. A method according to claim 3, wherein the intermediate network element comprises a proxy.

7. A method according to claim 3, wherein the intermediate network element does not establish a TCP connection with a source of the data packet.

8. A method according to claim 3, wherein the intermediate network element establishes a TCP connection with a source of the data packet.

9. A method according to claim 1, wherein determining whether the received data packet was fragmented or determining whether the data packet is expected to be fragmented comprises determining whether a fragmentation flag of the packet is set.

10. A method according to claim 1, wherein determining whether the received data packet was fragmented or determining whether the data packet is expected to be fragmented comprises determining whether the packet is to be fragmented by the determining unit.

11. A method according to claim 1, wherein determining whether the received data packet was fragmented or determining whether the data packet is expected to be fragmented comprises measuring the maximal transmission unit (MTU) of a path to the destination of the packet and determining whether the packet is larger than the determined MTU.

12. A method according to claim 11, wherein measuring the MTU is performed before receiving the packet.

13. A method according to claim 11, wherein measuring the MTU is performed after receiving the packet.

14. A method according to claim 1, comprising transmitting an error message to at least one end unit of the connection, instructing the end unit to use a maximal packet size included in the error message.

15. A method according to claim 14, wherein the maximal packet size included in the error message comprises the size of the received packet.

16. A method according to claim 14, wherein the maximal packet size included in the error message comprises a size different from the size of the received packet.

17. A method according to claim 16, wherein the maximal packet size included in the error message comprises a size determined as the maximum transmission unit (MTU) of a path from a unit performing the determination to a destination of the received packet.

18. A method according to claim 1, comprising identifying a subsequent request to form a subsequent connection by at least one of the end units of the disconnected connection and forcing the subsequent connection to use packets of a size up to a maximal size smaller than or equal to the size of the received packet.

19. A method according to claim 18, wherein identifying a subsequent request to form a subsequent connection by at least one of the end units of the disconnected connection comprises identifying a subsequent request to form a connection between end units of the disconnected connection.

20. A method according to claim 1, comprising registering the data connection of the received packet in the list of connections comprises registering the data connection according to an identity of a source of the packet.

21. A method according to claim 1, comprising disconnecting the connection to which the packet belongs, responsive to a determination that the received data packet was fragmented or is expected to be fragmented.

22. A method of avoiding packet fragmentation, comprising:

receiving a data packet belonging to a data connection;

determining whether the received data packet was fragmented or determining whether the received data packet is expected to be fragmented on the way to its destination; and

disconnecting the connection to which the packet belongs, responsive to a determination that the received data packet was fragmented or is expected to be fragmented.

23. A method according to claim 22, wherein disconnecting the connection comprises transmitting a reset message on the connection.

24. A method according to claim 22, wherein disconnecting the connection comprises discarding the received packet.

25. A method according to claim 22, transmitting a message to at least one end unit of the connection, instructing the end unit to use a maximal packet size included in the message.

26. A network element, comprising:

an input interface adapted to receive packets;

a determination unit adapted to determine, for at least some of the received packets, whether the packets were fragmented or whether the packets are expected to be fragmented on their way to their destinations; and

a discarding unit adapted to discard packets for which it was determined that the packet was fragmented or is expected to be fragmented.

27. A network element according to claim 26, wherein the network element comprises a load balancer.

28. A network element according to claim 26, comprising a transmission unit adapted to transmit error messages to sources of packets discarded by the discarding unit.

29. A method of establishing a connection between a client and a network element, comprising:

determining a minimum maximum transmission unit (MTU) between the network element and at least one server;

establishing a connection between the network element and the client; and

transmitting from the network element to the client a maximal size of packets to be transmitted on the established connection, the maximal size being determined responsive to the determined minimum MTU.

30. A method according to claim 29, wherein the maximal size of packets transmitted to the client comprises the minimal MTU value of the at least one server.

31. A method according to claim 29, wherein the at least one server comprises a plurality of servers and the maximal size of packets transmitted to the client comprises an MTU value of a server estimated to service the client.

32. A method according to claim 29, wherein determining the minimum MTU comprises referencing a predetermined list of MTUs of the at least one server.

33. A method according to claim 29, wherein determining the minimum MTU comprises transmitting MTU measurement packets to at least one of the servers.

34. A method of preventing fragmentation, comprising:

receiving a request to establish a connection;

comparing a value of at least one field of the request to a list of values of the field and respective maximal packet sizes; and

establishing a connection responsive to the received request, with a maximal packet size from an entry of the list matching the value of the at least one field from the received request.

35. A method according to claim 34, wherein the at least one field comprises a source address field.

36. A method according to claim 34, wherein the maximal packet size is for packets transmitted in the same direction as the received request to establish a connection.

37. A method according to claim 34, wherein receiving the request and comparing the value to the list are performed by an intermediate network, which is not an end unit of the connection.