Ideas for optimizations:

* transmit.c (SendFragments, IPSendComplete):
  Keep IPFRAGMENT_CONTEXT objects and PathMTU buffers in a pool


References:

RFC 791 - Internet Protocol
http://www.faqs.org/rfcs/rfc791.html

RFC 792 - Internet Control Message Protocol
http://www.faqs.org/rfcs/rfc792.html

RFC 793 - Transmission Control Protocol
http://www.faqs.org/rfcs/rfc793.html

RFC 826 - Ethernet Address Resolution Protocol
http://www.faqs.org/rfcs/rfc826.html

RFC 1122 - Requirements for Internet Hosts - Communication Layers
http://www.faqs.org/rfcs/rfc1122.html

RFC 1123 - Requirements for Internet Hosts - Application and Support
http://www.faqs.org/rfcs/rfc1123.html

RFC 2398 - Some Testing Tools for TCP Implementors
http://www.faqs.org/rfcs/rfc2398.html

RFC 2525 - Known TCP Implementation Problems
http://www.faqs.org/rfcs/rfc2525.html

RFC 2581 - TCP Congestion Control
http://www.faqs.org/rfcs/rfc2581.html