under which condition could the LDP session fall down if there is not failures on the hello adjacencies?

If I get your question right, the answer is the open message. The open message contains a field for My AS number which is used to identify if this is going to be an iBGP or eBGP. MPBGP is a different story because iBGP and eBGP can be MPBGP this depends on AFI/SAFI negotiations.

Let me know if you need more information….

Apart from this info i have a doubt regarding BGP establishment…can anybody please help?

How can we differentiate that Established BGP session is IBGP, EBGP or MBGP…..on which BGP message type or during establisment process (FSM) we can differnetiate whether its IBGP, EBGP or MBGP.

under which condition could the LDP session fall down if there is not failures on the hello adjacencies?

I have a related question concerning order of LDP Discovery Sources. Sometimes a link will show the “hard” (Interface when there is an LDP Adjacency) as the first Discovery and the “soft” (Targeted Hello) and sometimes they are reversed. My team was interested in why this is AND how we can change the order. We have been able to consistently make the “hard” second in the list by toggling the interface, but we have not been able to consistently move the “hard” discovery to the “top”. The most consistent method has been rebooting the router which a very disruptive method for a less than 75% probability of success.

Thank you very much, you are very welcomed, I am glade that I was informative.

I agree with you regarding the basics issue, and I believe that you’ll have 10 correct answers right and wrong are very relative, I enjoy understanding things from different prospectives, for example if we were talking about a protocol, I do care about the facts from the standards point of view, from the vendors point of view, from the end-user point of view and from any other point of view I can find out, in this way I can build my understanding.

Please do take care, enjoy and have a nice day.

BR,
Mohammed Mahmoud.

Another excellent explanation. Many thanks!!! Really appreciate you taking the time to contrast LDP and RSVP in explaining this.

It’s one of those things where the basics bug you. Take FEC as an example. I think if you ask 10 different people (who knows MPLS) what FEC means, you will get 10 different answers

Thanks again.

First of all thank you very much, actually writing a large scale networks design book is one of my life time goals, let’s see

Regarding the label distribution being opposite to the data flow, this is a typical networking behavior, the control plane always correlates to the data plane in an opposite direction, to explain this with a simple approach, imagine two routers having a dynamic routing protocol between each others, R2 has a certain subnet connected to it and thus it advertises this subnet to R1 (this is the control plane – the job of the routing protocol), and thus when R1 needs to forward packets to this subnet (the destination) it uses R2 as the next-hop (this is the forwarding/data plane – done according to the information learned from the control plane), this is the typical behavior of any control and forwarding plane, let it be a routing protocol or a label distribution protocol (LDP or RSVP – Actually RSVP follows the same logic, yes the head-end initiates the LSP via the PATH message, but the labels are signaled in an opposite direction from the tail-end to the head-end via the RESV message – again egress to ingress).

I promise that we are going to try to cover most of the interesting topics, we might start doing this via a requesting system, we’ll see.

I am glade that you are enjoying our posts, and I hope that we are informative.

BR,
Mohammed Mahmoud.