tcp in mixed internet and geo-satellite environments: experiences and results
DESCRIPTION
Cesar Marcondes, Anders Persson, M.Y. Sanadidi, Mario Gerla Computer Science Dept, UCLA, USA Rosario Firrincieli DEIS/ARCES, University of Bologna, Italy David R. Beering, Greg Romaniak Infinite Global Infrastructures, LLC, USA. - PowerPoint PPT PresentationTRANSCRIPT
Tridentcom 2006, Barcelona, SpainTridentcom 2006, Barcelona, Spain
TCP in Mixed Internet and GEO-TCP in Mixed Internet and GEO-
SatelliteSatellite
Environments: Experiences and Environments: Experiences and
ResultsResultsCesar Marcondes, Anders Persson, M.Y. Sanadidi, Mario Gerla
Computer Science Dept, UCLA, USA
Rosario Firrincieli
DEIS/ARCES, University of Bologna, Italy
David R. Beering, Greg Romaniak
Infinite Global Infrastructures, LLC, USA
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
OutlineOutline
Rationale
Overview
Methodology
Testbed description
Examples of results
– satellite channel characterization
– impact of satellite errors on TCP
– Performance Enhancing Proxies
Conclusions
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
RationaleRationale
TCP NewReno does not perform efficiently in large BDP
environments
Many studies address TCP in large BDP networks focusing
mainly on high capacity networks
It is necessary to study also high-delay environments such
as mixed satellite networks
However, satellite resources are very scarce and most
satellite TCP optimization rely only on simulation and
emulation tools
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
OverviewOverview
Over the period of a month, a measurement campaign on
a real satellite environment has been conducted
The goal was to determine TCP performance varying the
channel conditions (non-congestion errors, cross-traffic)
Moreover, state-of-the-art Performance Enhancing Proxies
(PEP) have been tested
Not only do we present our results, but we also describe
the complex testbed deployment, methodology and the
lessons that we learned
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
MethodologyMethodology
Limitation of experimental measures:– satellite services must be suspended during measures– availability of only few hours
Simulations allow a highly planned experiment outline selecting a limited number of scenarios to be tested
Measures are compared with simulation results– differences are investigated by means of emulations
ns-2simulations
IGI systemexperimental
measures
FreeBSDemulations
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
Testbed topologyTestbed topology
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
Sat channel characterization Sat channel characterization (1)(1)
GEO satellite link are usually very robust thanks to their physical layer codes. Link errors are very common when mobility and extreme weather conditions are involved
We forced errors on the satellite link by means of power adjustments on the modulators/demodulators
A constant rate stream of packets was used (UDP traffic)
Extremely high error rate = 92%Low error rate = 0.53%
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
Sat channel characterization Sat channel characterization (2)(2)
Packets are dropped in bulks showing a behavior similar to the 2-state Gilbert-Elliot channel model
Real measures gave us the guideline to reproduce this behavior in the simulator Average packet error rate = 0.1%
Measures drive simulations!
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
Impact of satellite errors on Impact of satellite errors on TCP TCP
TCP NewReno does not distinguish between congestion and link errors
As a consequence the congestion window is halved many times due to link errors
TCP Westwood is an example of TCP modification that distinguishes between congestion and link errors
Error level experienced across experiments
TCP performance under errors
Measures are close to simulations!
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
Cross traffic effectsCross traffic effects
The effects of a UDP spike traffic on TCP Westwood have been evaluated
Simulation Emulation
Emulation with fix
Simulations drive emulations!
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
PEP: description (1)PEP: description (1)
Based on the introduction of an intermediate agent
(proxy) which alters the end-to-end semantics of TCP
Tested PEPs implement a splitting approach and belong to
the category of transport layer PEP [RFC 3135]
IP
TCP
Application
IP
TCP
Application
TCP server(sender side)
TCP client (receiver side)PEP agent
(uplink gateway)
internet
PEP agent(downlink gateway)
internet
IP
TCP
IP
PEP TCP
IP
PEP TCP
IP
TCP
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
PEP: description (2)PEP: description (2)
Name Mentat SkyX ViaSat iPEP SaTPEP
Description Commercial box based on Linux
Commercial box based on Linux and
Solaris
Public module for ns-2 simulator
TCP variants on satellite link XTP, SCPS-TS TCP-XL SatPEP
Flow control technique Rate based
Window based
Window based Rate based
Error recovery technique SNACK ECN NACK
Fast Start (RFC 1644 -T/TCP)
Yes Yes No
Data compression Yes No No
Data prefetch Yes No No
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
PEP: results (1) PEP: results (1)
Three connections start with 30 s of delay each other– Adaptability
SaTPEP
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
SaTPEP
PEP: results (2)PEP: results (2)
Mentat SkyX
SaTPEP
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
PEP: results (3)PEP: results (3)
Mentat SkyX
SaTPEP
Mentat SkyX
Viasat iPEP
Measures are far from simulations!
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
ConclusionsConclusions
We had an opportunity to perform extensive tests on a mixed network composed by a real GEO satellite and high-speed Internet
Main contributions:– sharing our experiences on running an iterative
simulation/measures/emulation methodology– satellite channel errors characterization– analysis of TCP Westwood on a real satellite channel– studying/debugging of two PEP boxes (Mentat SkyX, Viasat
iPEP) Open issues:
– further optimization of TCP on satellite channel – evaluation of new architectures for mixed Internet and GEO
satellite environment
TCP in Mixed Internet and GEO-Satellite Environments: Experiences and Results
Rosario Firrincieli
Thanks!Thanks!
Rosario Firrincieli
PhD Student
DEIS/ARCES University of Bologna
http://www.arces.unibo.it