Transcript Direct Execution of OLSR MANET Routing Daemon in NS-3
Direct Execution of OLSR MANET Routing Daemon in NS-3
Evgeni Bikov, Pavel Boyko IITP RAS, Moscow
• • • Questions: – Can the ns-3-dce framework run unmodified OLSRd routing daemon? – Does it match the out of box ns-3 OLSR model?
– Can it be used instead of model in large scale simulation campaigns?
Answer: yes … almost
• MANET routing protocol models are difficult to verify.
Specification Model Implementation • 3X more verification when model coexists with the “real” implementation!
Direct Code Execution
• • Run [as much as possible] unmodified ”implementation” code instead of model in simulated environment. Methods: – Virtual machines; – Manual source modifications (AODV-UU); – Automatic source modifications (NSC).
• • • • http://code.nsnam.org/mathieu/ns-3-dce No source code patching: – custom ELF loader with automatic globalization; – custom process and thread management; – glibc API reimplemented to use NS-3 API; – netlink API reimplemented .
Shown to run Zebra routing daemon.
Now runs Linux kernel as well as user space applications.
• • • • • • http://olsr.org
Production quality OLSR implementation.
~80 KLOC in C, user space, portable, BSD license.
Widely used in community mesh networks, O(10K) installations worldwide: – http://guifi.net
12K+ operating nodes, Spain – http://funkfeuer.at
Austria Large number of RFC extensions; plugin architecture.
OLSRv2 implementation in progress.
Running OLSRd on NS-3-DCE
• • • OLSRd appeared to be quite demanding to glibc implementation quality (good test case) But finally it runs Now how to check that NS-3-DCE executes OLSRd correctly?
– read PCAPs; – compare to virtual machine execution; – compare to out of box NS-3 OLSR model.
OLSRd vs. ns3::olsr::RoutingProtocol
• • • • • Small static topologies Steady state simulation No traffic apart OLSR Observables: – routing tables @ all nodes; – – mean packet size (B); mean packet rate (1/s).
Results: – all routing tables match; – mean packet size and rate: up to 2X difference.
• • • Find and fix the differences between OLSRd and NS-3 OLSR model until observables match.
Differences found: – default timeouts – HELLO compression – message aggregation – message jitter OLSRd modified; model modified; model modified; OLSRd modified.
After calibration observables match within 1-5%.
Example: Message Jitter
RFC NS-3 OLSR model OLSRd
Comparison: Transient Behavior
• • • • • • 100 nodes Static random positions No traffic Mean known route length (top) Number of known destinations (bottom) Similar behavior, but difference >> stddev.
Comparison: Steady State
• • Good: average steady state route length matches.
Bad: up to 2x difference in average packet size and average packet rate.
• Calibration made for small networks does not help at larger scale. Need more accurate message compression and aggregation mechanisms in the model.
• OLSRd outperforms model at 100 nodes
• Use model at the early stages of MANET routing protocol design/research.
• Finally discard model and switch to DCE of implementation.
• Use calibration procedure in between to test model and implementation against each other.