KAIST EECS Computer Engineering Research Lab CORE A General Purpose Proxy Filtering M echanism Applied to the Mobile Envi ronment Bruce Zenel Jupyung Lee CoreLab, KAIST March 18. 2003
Jan 13, 2016
KAIST EECS Computer Engineering Research Lab
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
CORE
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
CORE
(Proxy MSR)
KAIST EECS Computer Engineering Research Lab
COREArchitecture: 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
KAIST EECS Computer Engineering Research Lab
CORE
(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
CORE
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 ClientClientClient
KAIST EECS Computer Engineering Research Lab
CORE
Performance of HTTP Filter
KAIST EECS Computer Engineering Research Lab
CORE
Performance of NFS Filter
KAIST EECS Computer Engineering Research Lab
CORE
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