[ns] Questions about MIP

[Diepchi T Tran <Diepchi.T.Tran@lerc.nasa.gov>]

Hi Marta, Satish, Chieh-Yih,

While I am working on my simulation, I see followed strange behavior of
basestations that I can not tell if it is caused by bugs or there are
reasons for it:

After mobile node move away from HA, packets destinated to mobile node are
sent to HA for encapsulation and forwarded to FA. I see that some packets
are encapsulated and forwarded to FA right after they received by HA as
following: 


r 86.11296 2 7 tcp 1000 ------N 1 0.0.0.0 5.0.1.2 8 518
+ 86.11296 7 2 tcp 1020 ------N 1 0.0.0.1 6.0.0.1 8 518
- 86.11296 7 2 tcp 1020 ------N 1 0.0.0.1 6.0.0.1 8 518

Then a next packet ( packet # 9) comes in to HA for encapsulation. But
instead of be encapsulated and forwarded to FA, that packet is sent up to
RTR level as following:   

r 87.11296 2 7 tcp 1000 ------N 1 0.0.0.0 5.0.1.2 9 519
r 87.112960411 _7_ RTR  --- 519 tcp 1000 [0 0 0 0] ------- [0:0 20971521:2
29 0] [9 0] 0 0
f 87.112960411 _7_ RTR  --- 519 tcp 1000 [0 0 0 0] ------- [0:0 20971521:2
28 20971521] [9 0] 0 0
         

Then it is dropped later because of CBK


D 87.142571411 _7_ MAC  RET 0 MAC 44 [11be 4 0 0]
D 87.142571411 _7_ RTR  CBK 519 tcp 1000 [a2 4 0 800] ------- [0:0
20971521:2 28 20971521] [9 0] 0 0
D 87.142571411 _7_ MAC  --- 519 tcp 1000 [a2 4 0 800] ------- [0:0
20971521:2 28 20971521] [9 0] 0 0      


First, I think because of the congestion on the link between HA and FA at
the time packet # 9 received by HA, HA holds that packet to wait for the
link is cleared. However, the packet is dropped later because of CBK , so
it looks like, instead of encapsulating and forwarding the packet, the HA
tries to send packet # 9 to mobile node. But it does not success because
the mobile node is already move out of HA's domain. Therefore, I think this
behavior of HA is caused by a bug. 


Do you think packet # 9 is sent up to RTR level instead of be encapsulated
and forwarded to FA like packet # 8 because of a bug or congestion or other
reasons? Please help


I saw a lot of packets (tcp and udp) in my trace file are dropped because
of CBK that I think they should not be dropped. Do you know which files
that I need to look at such that I can find out the reasons for dropping a
packet caused by CBK?.

Thank you very much,
Cindy















Diepchi Tran 
Phone (216) 433-8861
Fax   (216) 433-8705