Transcript Revolutionary Internet technology growth with

CORE
A General Purpose Proxy Filtering Mechanism
Applied to the Mobile Environment
Bruce Zenel
Jupyung Lee
CoreLab, KAIST
March 18. 2003
KAIST EECS Computer Engineering Research Lab
CORE
Contents
• Introduction
• Architecture
– PMICP
– Proxy Server
– Adaptation through Filter Control
• Designed and Implemented Filters
• Evaluation
– HTTP filter
– NFS filter
– TCP filter
• Conclusion & Future Work
KAIST EECS Computer Engineering Research Lab
CORE
Introduction
• Mobile environment
– Slower, more costly, less reliable, less secure than WAN, LAN…
– Heterogeneity problem : hosts move unpredictably in networks
which have different speed, cost, security, loss rate
• Proxy improves the mobile environment
– Drop / Compress / Delay / Cache data
• MPEG / HTTP, NFS / POP / TCP
– Act as substitute for mobile client
• ICMP ECHO request
– Use a different transport protocol(or parameter settings)
– Generally… : perform trading off computation for communication
* Minimize server/client modification
KAIST EECS Computer Engineering Research Lab
CORE
Introduction (cont’)
• Filter : program downloading & executing on proxy
– Often application specific
– Dynamically control filter behavior
• Contribution of this paper
– Propose ‘general purpose proxy filtering mechanism’ applied to the
mobile environment
– Apply it to the HTTP, NFS, TCP
KAIST EECS Computer Engineering Research Lab
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Architecture: PMICP
• Problem:
– All traffic from/to MH must past through a single gateway
– But mobile protocol* supports host mobility
• Keep track of the location of the MH
• Using Mobile Support Routers(MSR)
• Solution
– New Protocol : PMICP**
• Each MH choose Proxy MSR(PMSR)
• PMICP guarantees that all traffic from/to MH will pass through PMSR
* Proxy filter runs on PMSR
* Columbia Mobile IP Protocol
** Proxy Mobile Internetworking Control Protocol
KAIST EECS Computer Engineering Research Lab
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(Proxy MSR)
KAIST EECS Computer Engineering Research Lab
CORE
Architecture: Proxy Server
• High Level Proxy
– Use filter insertion
• Low Level Proxy
– LLP packet queue is created
configured.
– It contains matching criterion
– If criterion is matched, filter is
allows to read/write LLP
packet queue
* Analogous to socket program
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(Filter Insertion)
* Kernel on Proxy & MH may be modified
* Server notices no change
KAIST EECS Computer Engineering Research Lab
CORE
Architecture: Adaptation through Filter Control
• Event Registry(ER)
– Register in certain events
•
•
•
•
Change in network bandwidth
Network interface information
Change in MH battery power
MH location
– Notified when these events occur
KAIST EECS Computer Engineering Research Lab
CORE
Designed and Implemented Filters
•
•
•
•
•
HTTP: compress header/body of HTTP messages
MPEG: drop intermediate MPEG frames
SMTP: drop all multimedia data
NFS: compress file data
ICMP: provide replies to queries
• TCP
– Cache unacknowledged TCP to MH
– Perform local re-TX when packet loss is detected
• arrival of a duplicate ack, local timeout
– Not break the end-to-end semantics of TCP
– Originally from “Improving TCP/IP Performance over Wireless
Networks”
KAIST EECS Computer Engineering Research Lab
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Evaluation
• 10Mbps Ethernet vs. 2Mbps Wavelan vs. 33.3Kbps SLIP
• HTTP filter
– compress text file using ZLIB or LZO
– not compress image file
– Primary proxy as compressor, secondary as decompressor
• Provide client transparency
• NFS filter : compress text/binary files using ZLIB or LZO
• TCP filter : use unacknowledged packet caching
Server
Proxy
Gateway
Client
Client
Client
KAIST EECS Computer Engineering Research Lab
CORE
Performance of HTTP Filter
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Performance of NFS Filter
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Performance of TCP Filter
KAIST EECS Computer Engineering Research Lab
CORE
Conclusion & Future Work
• General Purpose Proxy Mechanism
• Author’s future work
– End-to-End semantics
• High level proxy breaks the end-to-end semantics of TCP
– Security
• Message security between proxy & MH
• Filter code security
– Proxy mobility
– # proxies
– Adapt protocol / application
KAIST EECS Computer Engineering Research Lab