Direct Execution of OLSR MANET Routing Daemon in NS-3

Evgeni Bikov, Pavel Boyko IITP RAS, Moscow

Overview

• • • 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

Motivation

• 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).

NS-3-DCE Framework

• • • • 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.

OLSRd

• • • • • • 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.

Calibration

• • • 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.

Comparison: Performance

• OLSRd outperforms model at 100 nodes

Conclusions

• 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.