RFC 3234 (rfc3234) - Page 2 of 27
Middleboxes: Taxonomy and Issues
Alternative Format: Original Text Document
RFC 3234 Middleboxes: Taxonomy and Issues February 2002
Table of Contents
1. Introduction and Goals......................................... 3
1.1. Terminology.................................................. 3
1.2. The Hourglass Model, Past and Future......................... 3
1.4. Goals of this Document....................................... 4
2. A catalogue of middleboxes..................................... 5
2.1 NAT........................................................... 6
2.2 NAT-PT........................................................ 7
2.3 SOCKS gateway................................................. 7
2.4 IP Tunnel Endpoints........................................... 8
2.5. Packet classifiers, markers and schedulers................... 8
2.6 Transport relay............................................... 9
2.7. TCP performance enhancing proxies............................ 10
2.8. Load balancers that divert/munge packets..................... 10
2.9. IP Firewalls................................................. 11
2.10. Application Firewalls....................................... 11
2.11. Application-level gateways.................................. 12
2.12. Gatekeepers/ session control boxes.......................... 12
2.13. Transcoders................................................. 12
2.14. Proxies..................................................... 13
2.15. Caches...................................................... 14
2.16. Modified DNS servers........................................ 14
2.17. Content and applications distribution boxes................. 15
2.18. Load balancers that divert/munge URLs....................... 16
2.19. Application-level interceptors.............................. 16
2.20. Application-level multicast................................. 16
2.21. Involuntary packet redirection.............................. 16
2.22. Anonymisers................................................. 17
2.23. Not included................................................ 17
2.24. Summary of facets........................................... 17
3. Ongoing work in the IETF and elsewhere......................... 18
4. Comments and Issues............................................ 19
4.1. The end to end principle under challenge..................... 19
4.2. Failure handling............................................. 20
4.3. Failures at multiple layers.................................. 21
4.4. Multihop application protocols............................... 21
4.5. Common features.............................................. 22
5. Security Considerations........................................ 22
6. Acknowledgements............................................... 23
7. References..................................................... 23
Authors' Addresses................................................ 26
Acknowledgement................................................... 26
Full Copyright Statement.......................................... 27
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