Systems and methods for handling packet fragmentation

• US 7,616,562 B1
• Filed: 05/22/2007
• Issued: 11/10/2009
• Est. Priority Date: 03/22/2002
• Status: Active Grant

• Current Assignee: Juniper Networks Incorporated
• Original Assignee: Juniper Networks Incorporated
• Inventors: Libby, Jeffrey G., Lim, Raymond M.
• Primary Examiner(s): Trost, IV; William
• Assistant Examiner(s): JAIN, RAJ K
• Application Number:
  US11/751,952
• Time in Patent Office: 903 Days
• Field of Search: None
• US Class Current: 370/229
• CPC Class Codes: H04L 45/60 Router architectures
• 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 49/3009 Header conversion, routing tables or routing tags
• CPC Class Codes: H04L 49/3072 Packet splitting
• 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 69/166 IP fragmentation; TCP segmentation

Abstract

A packet header processing engine receives a header of a packet. The received header includes a size of the packet. A maximum transfer unit size of a destination interface of the packet may be determined. The packet header processing engine determines whether the size of the packet exceeds the maximum transfer unit size of the destination interface. If the size of the packet does not exceed the maximum transfer unit size of the destination interface, the packet header processing engine generates a new header from the received header. If the size of the packet exceeds the maximum transfer unit size of the destination interface, the packet header processing engine generates a fragment header from the received header. The packet header processing engine may recycle the fragment header for further processing in addition to forming a first fragment packet from the fragment header.

Claims

1. A method performed by a packet forwarding engine in a routing system, the method comprising:

receiving, at the packet forwarding engine, a header of a packet, the received header including a size of the packet and a destination interface of the packet;

determining, by the packet forwarding engine and based on the received header, whether the size of the packet exceeds a maximum transfer unit size of the destination interface of the packet; and

generating, by the packet forwarding engine, new layer 3 header information based on the received header and the determining whether the size of the packet exceeds the maximum transfer unit size, where the new layer 3 header information includes a checksum that is updated concurrently as the new layer 3 header information is being generated.

2. The method of claim 1, further comprising:

generating a new header from the new layer 3 header information if the size of the packet does not exceed the maximum transfer unit size of the destination interface.

3. The method of claim 2, further comprising:

forming a packet including the new header.

4. The method of claim 1, further comprising:

generating a first fragment header from the new layer 3 header information if the size of the packet exceeds the maximum transfer unit size of the destination interface.

5. The method of claim 4, where the first fragment header includes a size of a remaining portion of the packet.

6. The method of claim 4, where the first fragment header includes information from which a size of a remaining portion of the packet may be determined.

7. The method of claim 4, where the first fragment header includes information indicating that the packet has been fragmented.

8. The method of claim 4, further comprising:

forming a first fragment packet including the first fragment header.

9. The method of claim 4, further comprising:

sending the first fragment header of the packet for further processing;

receiving the first fragment header, the first fragment header including information about a size of a remaining portion of the packet and the maximum transfer unit size of the destination interface; and

determining whether the size of the remaining portion of the packet exceeds the maximum transfer unit size of the destination interface.

10. The method of claim 9, further comprising:

generating a new header from the first fragment header if the size of the remaining portion of the packet does not exceed the maximum transfer unit size of the destination interface; and

forming a second fragment packet including the new header.

11. The method of claim 9, further comprising:

generating a second fragment header from the first fragment header if the size of the remaining portion of the packet exceeds the maximum transfer unit size of the destination interface.

12. A device comprising:

means for receiving a header of a packet, the received header including a size of the packet and a destination interface of the packet;

means for determining, from the header of the packet, whether the size of the packet exceeds a maximum transfer unit size of the destination interface; and

means for generating new layer 3 header information based on the received header and the determining whether the size of the packet exceeds the maximum transfer unit size; and

means for generating a checksum that is updated concurrently as the new layer 3 header information is being generated.

13. The device of claim 12, further comprising:

means for generating a new header from the new layer 3 header information if the size of the packet does not exceed the maximum transfer unit size of the destination interface.

14. The device of claim 12,

where the new layer 3 header information further includes a checksum that is updated concurrently as the new layer 3 header information is being generated.

15. The device of claim 14, where the first fragment header includes a size of a remaining portion of the packet.

16. The device of claim 14, where the first fragment header includes information from which a size of a remaining portion of the packet may be determined.

17. A method performed by a packet forwarding engine in a routing system, the method comprising:

receiving, at the packet forwarding engine, a header of a packet, the received header including a size of the packet and a destination interface of the packet;

simultaneously generating, by the packet forwarding engine, new layer 3 header information based on the received header and whether the size of the packet exceeds a maximum transfer unit size;

simultaneously generating, by the packet forwarding engine, a checksum and other new layer 3 header information if the size of the packet does not exceed the maximum transfer unit size of the destination interface; and

generating, by the packet forwarding engine, a first fragment header from the new layer 3 header information if the size of the packet exceeds the maximum transfer unit size of the destination interface.

18. The method of claim 17, where the first fragment header includes a size of a remaining portion of the packet.

19. The method of claim 17, where the first fragment header includes information from which a size of a remaining portion of the packet may be determined.

20. The method of claim 17, where the first fragment header includes information indicating that the packet has been fragmented.