CORE KAIST EECS Computer Engineering Research Lab A General Purpose Proxy Filtering Mechanism Applied to the Mobile Environment Bruce Zenel Jupyung Lee CoreLab, KAIST March

CORE KAIST EECS Computer Engineering Research Lab Contents Introduction Architecture –PMICP –Proxy Server –Adaptation through Filter Control Designed and Implemented Filters Evaluation –HTTP filter –NFS filter –TCP filter Conclusion & Future Work

CORE KAIST EECS Computer Engineering Research Lab 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

CORE KAIST EECS Computer Engineering Research Lab 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

CORE KAIST EECS Computer Engineering Research Lab 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

CORE KAIST EECS Computer Engineering Research Lab (Proxy MSR)

CORE KAIST EECS Computer Engineering Research Lab 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

CORE KAIST EECS Computer Engineering Research Lab (Filter Insertion) * Kernel on Proxy & MH may be modified * Server notices no change

CORE KAIST EECS Computer Engineering Research Lab 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

CORE KAIST EECS Computer Engineering Research Lab 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”

CORE KAIST EECS Computer Engineering Research Lab 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 ServerProxyGateway Client

CORE KAIST EECS Computer Engineering Research Lab Performance of HTTP Filter

CORE KAIST EECS Computer Engineering Research Lab Performance of NFS Filter

CORE KAIST EECS Computer Engineering Research Lab Performance of TCP Filter

CORE KAIST EECS Computer Engineering Research Lab 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