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Middle Boxes

Middle Boxes Lixia Zhang UCLA Computer Science Dept Sprint Research Symposium March 8-9, 2000 What are middle boxes? What are the end boxes? server client Internet IP delivery Back 20 years… What's on the net - servers/clients (e.g. telnet, ftp, email) - later: peers (e.g. VT)

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Middle Boxes

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  1. Middle Boxes Lixia Zhang UCLA Computer Science Dept Sprint Research Symposium March 8-9, 2000

  2. What are middle boxes?

  3. What are the end boxes? server client Internet IP delivery • Back 20 years… • What's on the net • - servers/clients (e.g. telnet, ftp, email) • - later: peers (e.g. VT) • data delivery between the end boxes • directly

  4. The Role of IP Delivery IP delivers packets from end to end • the ends are defined by the communicating application process • the ends are indicated by the source and destination addresses in the IP header server client routers

  5. What are middle boxes? middle box In the early days: always connected Email recipient Email sender • data is no longer delivered between the two end boxes by direct IP path • The first middleman: email server server client

  6. What are middle boxes? middle box always connected email server email recipient email sender • data is no longer delivered between the two end boxes by direct IP path • The first middleman: email server server client As time went: Intermittent connectivity

  7. Every coin has two sides • Gain from having such a middlebox: solved the asynchrony problem between the two ends of email delivery • Loss for having a box in the middle: • more parts in the system to mingle with • more points of potential failures email server email recipient email sender

  8. The position of email serverin the IP architecture • An application level box • email sender talks to email server explicitly • email recipient fetches email from the server explicitly • in another word, not a "transparent" box email server email recipient email sender

  9. What we've seen in last couple of years Web proxy client Web server • A lot more middle boxes • Web proxies • "transparent" Web caches • portals Packet hijacking! ("for your benefit")

  10. And more middleboxes yet to come e.g. Proxy servers to facilitate mobile wireless devices and mobile users in handling • intermittent connectivity • location tracking • link QOS constraint • session migration

  11. What we've seen...... • Growing up of the Internet, of course • need for scalable data dissemination • large number of clients requesting same data • requests coming in asynchronously • need for information discovery/sorting • need for authentication/security and all other kinds of services

  12. Challenges from growth • large number of clients, large number of mobile users, large number of servers too • How to do it right? So far pretty much "one hundred flowers blooming" • Web proxies • abuse DNS for load balancing • "transparent" caching • "layer switching", 3 < < 10?

  13. What's coming Big part of the society moving online • what makes up the society & business market: mostly middlemen • largely missing on the Internet • the reason that the Internet, by and large, does not look user-friendly to most people Prediction • a lot more middle boxes • IP packet delivery infrastructure fades into background—ubiquitous IP connectivity everywhere

  14. "Internet architecture" ? email WWW phone... SMTP HTTP RTP... TCP UDP… IP ethernet PPP… CSMA async sonet... copper fiber radio... User programs application protocols transport protocols IP various networks • Where in the architecture do those new middle boxes belong to? • For now: nowhere, or everywhere • haven't you heard • the hot buzzword • "transparency"? Does that raise a concern? YES

  15. Concerns about transparent middleboxes • "transparent" middleboxes considered harmful • packet hijacking versus system manageability • Users: being in control versus being controlled • Sticking to the layered protocol architecture considered necessary

  16. Where middle boxes belong toin the Internet architecture • should be application level boxes • being visible to end users • Middleboxes and end-to-end principle: consider middle boxes as one "end" of "end-to-end" • e.g. the mail server in email delivery

  17. Middleboxes: gains • Keep the waist of the hour-glass thin • manageable, scalable, robust connectivity • help the Internet scale with growing applications & client population • Provide real services, all kinds of them • personalized portals • heterogeneity • building new services from existing applications

  18. Some potential losses(or things we need to pay attention) • Dependency on those middleboxes • increased complexity • increased vulnerability • "directory-enabled network": the network is gone when directory crashes, even if all switches are up • a robust, self-configured, self-organizing middlebox infrastructure can lead to higher availability and more robustness • more complex security and trust model • impact on data integrity

  19. Summary • Finally the Internet is growing up! • Past efforts mostly on packet delivery • Now people start making money out of this packet delivery service • middle boxes are a must • Warning: pay attention to architecture • Right way out: building application level infrastructures on top of the packet delivery infrastructure

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