[Olsr-dev] Network topology if there is a node get down?

[Agung Septiadi]

I have OLSR network which has topology like this.
node A <-> node B <-> node C <-> node D (gateway) <------> internet
Node A, node B, node C, and node D using Ubuntu 8,04
and I accessed video streaming to our Youtube-like website in our intranet
and Yahoo messenger with Pidgin from Node A to Internet via Node B, Node C
and Node D (gateway)

Then, I turned Node E (WindowsXP) on which is located between Node A and
Node D. Network Topology was becoming like this
node A <-> node B <-> node C <-> node D <------> internet
node A <-----------> node E <--------> node D <------> internet

I  captured ping activity from node A to node D. The result is showed below
(Node D is 192.168.100.1 and Node E is 192.168.100.15)

64 bytes from 192.168.100.1: icmp_seq=211 ttl=62 time=3.69 ms
64 bytes from 192.168.100.1: icmp_seq=212 ttl=62 time=5.11 ms
64 bytes from 192.168.100.1: icmp_seq=213 ttl=62 time=4.21 ms
64 bytes from 192.168.100.1: icmp_seq=214 ttl=62 time=4.55 ms
>From 192.168.100.15: icmp_seq=215 Redirect Host(New nexthop: 192.168.100.1)
64 bytes from 192.168.100.1: icmp_seq=215 ttl=63 time=5.25 ms
>From 192.168.100.15: icmp_seq=216 Redirect Host(New nexthop: 192.168.100.1)
64 bytes from 192.168.100.1: icmp_seq=216 ttl=63 time=6.17 ms
>From 192.168.100.15: icmp_seq=217 Redirect Host(New nexthop: 192.168.100.1)
64 bytes from 192.168.100.1: icmp_seq=217 ttl=63 time=4.74 ms
>From 192.168.100.15: icmp_seq=218 Redirect Host(New nexthop: 192.168.100.1)
64 bytes from 192.168.100.1: icmp_seq=218 ttl=63 time=4.37 ms


Sequence no.214 was still routed via node B and node C
On Sequence no 215, packet routing had been diverted via node D
Packet routing from node A to node D had been diverted (from node A -> node
B -> node C ->node D -> internet To node A -> node E -> node D -> internet)
smoothly
Buffering process on streaming and Pidgin was not disconnected at all.

If I turned Node E down, First, there was ping loss (I think ping loss is
normal when there is node who has down, CMIIW)
Here is the ping activity when I had turned node E down

>From 192.168.100.15: icmp_seq=383 Redirect Host(New nexthop: 192.168.100.1)
64 bytes from 192.168.100.1: icmp_seq=383 ttl=63 time=192 ms
>From 192.168.100.15: icmp_seq=384 Redirect Host(New nexthop: 192.168.100.1)
64 bytes from 192.168.100.1: icmp_seq=384 ttl=63 time=129 ms
>From 192.168.100.15: icmp_seq=385 Redirect Host(New nexthop: 192.168.100.1)
64 bytes from 192.168.100.1: icmp_seq=385 ttl=63 time=103 ms
>From 192.168.100.15: icmp_seq=386 Redirect Host(New nexthop: 192.168.100.1)
64 bytes from 192.168.100.1: icmp_seq=386 ttl=63 time=89.8 ms
64 bytes from 192.168.100.1: icmp_seq=506 ttl=62 time=5.26 ms
64 bytes from 192.168.100.1: icmp_seq=507 ttl=62 time=5.10 ms
64 bytes from 192.168.100.1: icmp_seq=508 ttl=62 time=6.65 ms
64 bytes from 192.168.100.1: icmp_seq=509 ttl=62 time=4.77 ms

Sequence no.386 was still using node B and node C's link
There are ping losses from sequence 387 to seq no. 505 (there are about 119
packet losses) (FYI, I set HelloValidityTime to 120 s on every node)
On this state, buffering process was stopped, and Pidgin was still connected
but could not send any messages to everybody

After about 120 secs, Ping routing had been been diverted via node B and
node C again, (Start from icmp_seq=506)
But, buffering processing on the video streaming completely stopped and
Pidgin was disconnected.

Why all applications was disconnected after there is a node get down,
whereas all applications was still connecting if there are node get up
offering better link?
Was OLSR doing something wrong?

Here are my olsrd.conf on every node without commenting

DebugLevel    0
Interface "ath0"
{
    HelloInterval        6.0
    HelloValidityTime        120.0
    TcInterval            3.0
    TcValidityTime        300.0
    MidInterval            15.0
    MidValidityTime        300.0
    HnaInterval            10.0
    HnaValidityTime        120.0
}
LinkQualityFishEye 1
LinkQualityDijkstraLimit 3 3.0
IpVersion    4
ClearScreen     yes
Hna4
{
}
Hna6
{
}
AllowNoInt    yes
Willingness        7
IpcConnect
{
     MaxConnections  0
     Host            127.0.0.1
}
UseHysteresis    no
LinkQualityLevel    2
LinkQualityWinSize    100
Pollrate    0.1
TcRedundancy    2
MprCoverage    5

On Gateway (Node D), I have added HNA configuration
Hna4
{
  0.0.0.0 0.0.0.0
}
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