Network Performance Management
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Transcript of Network Performance Management
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Network Performance Management
S. Keshav
C/NRG(with Rosen Sharma, Andy Choi, Wilson
Huang, Lili Qiu, Russell Schwager, Rachit Siamwalla, Jia Wang, and Yin Zhang)
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Motivation
Networks are increasing in breadth…. – greater density of connections– PCs come with built-in networking– ADSL and cable modems– wireless networking
as well as in depth– variety of qualities, policies, and media
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The current situation
Loss of productivity from– slow file access – web site disconnection– slow access to a web site– no one knows exactly why!
Greater breadth and depth => even more dependency on the network => even more problems
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Is QoS enough?
Lots of research in the area of QoS– RSVP, differential service etc. provide a good
overall user experience, one stream at a time– Is QoS all there is to a good user experience?
An incorrect reservation poor service for one stream
A misconfigured router complete loss of service to one or more ports!
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Aha!
User experience is affected more by ‘mundane’ network management than by ‘exotic’ QoS research
This motivates our entire research effort
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Why networks fail
Link or router failure Transient overload Unanticipated increase in load Misconfiguration
Increasingly harder to detect
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Need Better Network Management Current approaches
– GUI-centric– lots of flashing lights, but no intelligence
Can detect failures but...– ad hoc capacity planning– ad hoc configuration
• no way of testing other than “just try it!”
Can’t manage network performance
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Performance management
Topology discovery
Fix problems (AI and simulation)
Collect statistics (monitoring)
Identify problems (display and simulation)
Configure new hardware (simulation)
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Discovery: Project Octopus
Permanent Set
Temporary Set
Heuristic
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Techniques
DNS-ls SNMP Random probe Traceroute Directed broadcast ping
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Results
Have automatically discovered entire CS department topology
As well as entire Stanford topology (> 220 subnets)
Cornell topology is being discovered as we speak!– info being shared with CIT
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Monitoring
A PERL script uses SNMP and queries a router using various MIB entries.
The MIB entries are stored in an input file. The values gathered from the router are
stored in a file. The script works on both UNIX and
WinNT.
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Monitoring (contd.)
Other PERL scripts parse the data and convert it to other formats.
Currently supported formats:– HTML - The data is presented in a table format
in HTML.– GNUPlot graphs - The data can be graphed or
saved in pbm format
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A Case Study: CSGate2
From 2/19/98 to 2/23/98, the router CSGate2 was probed every 5 minutes recording various statistics on the data coming into and going out of the router.
Incoming bytes at CSgate2
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Display goals
We want to display multiple views Views should be dynamic Shoul allow expansion and contraction Rapid creation of user interface Reusability of GUI components
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Solution: Script Java
Component-based system Reusable manageable components Can build large manageable applications Sharing over the web Record and playback
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Architecture
Use JavaScript/Visual Basic as the scripting language
Use Java to write components Create a adapter hierarchy for the current
AWT components
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Script Java
Objects
HTML pages Java structures
intelligence protection by
namespace
Data Model
linearized data structures
java perl javascript
Communication Abstraction
multicast channels
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Advantages
Allows us to glue components using a scripting language, allowing rapid prototyping and development
New components can be easily integrated For large applications, a lot of the
complexity and chaos can be taken out of scripting
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Advantages(cont.)
JavaScript can be streamed from the server, allowing for presentations and sharing
Dynamic Html– layers are windows– these windows render html
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Storage goals
We need to store topology and monitoring results somewhere
Database: too structured and too much overhead
File system: not enough semantics Idea: treat URL as a file system link and
HTML tags as associated semantics
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WebFS
HTML tags allow arbitrary semantic abstractions
Manipulate these abstractions to present a virtualized file system
grep -headings *.html sed ‘/<annot tag=foo>/jdbc(“tags.db”,
“foo”)/’
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The magic bullet: simulation
Realistic simulation where networking subsystem interacts with other parts of kernel
Fast simulation for large networks ( > 1000 hosts)
Hide the abstraction of simulated network, same API as system calls
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FreeBSD kernel User Space
Kernel core
Telnetdping
gatedmachine
Kernel wrapper
msg
Network Stack
Telnetdping
gated
Sockets
traps
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Simulated machine
Task based approach– a trap sends a message
to kernel
– an upper call is a message from kernel
All components of simulated machine live on same process
Kernel core
Telnetdping
gated
machine
Kernel wrapper
msg
Simulated link
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More on simulated machine
Capture network related system calls, file descriptor auto re-mapping.
Virtual file system root
Single-thread kernel, therefore no need for locking
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Simulated network
Kernel core
Telnetd ping
gatedmachine
msg
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Integrating with real network
Use U-Net to interact with external device
Router has the illusion of being in a physical network
Test equipment before actual deployment
Physical RouterUnet
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Tradeoffs
Balance between realism and speed
– Using FreeBSD as basis for realistic simulation
– Using session level simulation to speed up
Ease of porting applications
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Open issues
Fault identification– Bayesian networks?– Ensemble of experts?– Other AI approaches?
How to do session-level simulation? Configuring real systems
– IP9000