I'm currently prepare my CCNP, ONT 642-845 certification Exam.
I have question about the Frame Relay Explicit Congestion Notification (BECN and FECN).
I had provide a small visio plan to make my question more easier to explain.... (see attached files)
My understanding about BECN & FECN notification is this :
If PC1 is sending data to PC4 through router 1 to 4. When data pass through congestion 128K link Router2 will generate BECN and send this to Router1 also Router2 generate FECN and send it to Router4 to notify the upper layer protocol they will expected some delay to received data from PC1. When Router1 received BECN, Router1 start to shape his interface to slowdown communication to PC4. But, Router4 have not to change anything in is shaping configuration.
Now if I'm correct with this everything is good to me. What is not clear to is the last sentence in the following text :
"Frame Relay traffic shaping controls Frame Relay traffic only and can be applied to a Frame Relay subinterface or Frame Relay DLCI. Whereas Frame relay traffic shaping supports Frame Relay fragmentation and interleaving (FRF.12), class-based traffic shaping does not. On the other hand, both class-based traffic shaping and Frame Relay traffic shaping interact with and support Frame Relay network congestion signals such as BECN and forward explicit congestion notification (FECN). A router that is receiving BECNs shapes its outgoing Frame Relay traffic to a lower rate. If it receives FECNs, even if it has no traffic for the other end, it sends test frames with the BECN bit set to inform the other end to slow down."
copy paste form : CCNP ONT Official Exam Certification Guide
Author : Amir S. Ranjbar, CCIE No. 8669
First Printing: May 2007
Page : 167
"If it receives FECNs, even if it has no traffic for the other end, it sends test frames with the BECN bit set to inform the other end to slow down."
I'm understand when Router4 received the FECN, router4 will send BECN to some others....
To which one exactly ?
After this exchange of BECN FECN, how should I expected to know where is the congested link ?
Is also Router4 send FECN, when this stop ?
I don't understand why router4 send BECN to someone else....
can somebody help me ?
Thanks a lot !
P.S.: Please excuse me for my English, I'm a French peoples.
Just to let you know got an e-mail back from Dan Bruhn, NetPro moderator -
We had a code change last week that was causing these problems. We rolled back the code change so they should be resolved. If you're still seeing issues please let me know. Thanks again for passing these issues along.