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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

Middle Boxes

Lixia Zhang

UCLA Computer Science Dept

Sprint Research Symposium

March 8-9, 2000

what are the end 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)
  • data delivery between the end boxes
  • directly
the role of ip delivery
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

what are middle boxes5
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

what are middle boxes6
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

every coin has two sides
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

the position of email server in the ip architecture
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

what we ve seen in last couple of years
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")

and more middleboxes yet to come
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
what we ve seen
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
challenges from growth
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?
what s coming
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
internet architecture
"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

concerns about transparent middleboxes
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
where middle boxes belong to in the internet architecture
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
middleboxes gains
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
some potential losses or things we need to pay attention
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
summary
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