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Bronze

MPLS TE Bandwidth and Priority

Hi everybody

 

Hopefully, everyone is doing great.  I stumbled upon the following link on MPLS TE bandwidth and priority:

 

http://blog.ipexpert.com/2009/05/27/mpls-te-bandwidth-and-priority/

 

it was a very good read.  But I am left with one question. How does R2 decide which tunnel to drop? In the example, R2 drops tunnel 1, but how does R2 decide which one to drop?

 

 

 

Thanks and have a great sunday

5 REPLIES

Hello,A good blog thanks for

Hello,

A good blog thanks for sharing, What I understood from this is In Router 5 and 6 tunnel 1 has got the bandwidth which is required, hence the tunnels were up but Router 4 has not got the bandwidth which is required, hence the tunnel has not come up.

But the point is when the tunnel's priority in Router 4 has changed then how come tunnel in Router 5 has got down and Router 6's tunnel is still up. why did it not happened vice versa.

Is the luck of R5 is bad?

BR

Thanveer

Regards Thanveer "Everybody is genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is a stupid."
Bronze

Hi Tanveer.Thanks for your

Hi Tanveer.

Thanks for your response. My apology for a late reply.( did not have good internet connection where I am staying for my  training, in fact I cannot even go the link that i posted, it is that slow :)

Uncle Sam needs to spend some money to upgrade the bandwidth :)

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

 

I will try again tomorrow.

 

Hopefully we will sort this thing out.

 

Have a great day.

 

 

 

 

 

Sure Dear, we can sort it IA.

Sure Dear, we can sort it IA.

Regards Thanveer "Everybody is genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is a stupid."
Bronze

Hi Thanveer I hope you are

Hi Thanveer

 

I hope you are doing fine.  Here is what i found  in a book ( traffic engineering with MPLS by Eric, Ajay, great book, still reading it)

 

There are two priorities:

1) set up priority

2) hold prioritity

 

Based on the book the code works this way

 

Imagine we have two tunnels already established and are passing through R3

t1, set up priority 6 hold priority 5

t2 set up priority 6 hold priority 4

 

Let say R3 just receives a RSVP path  request for  a new tunnel, lets call it tunnel 3 with set up priority 4 hold priority 6. This tunnel requires a bandwidth which R3 can not accommodate without dropping one of the established tunnels.

 

Router will take t3's set up priority ( 4) and compares it against the current  established tunnel's hold priorities where lower the number means higher the priority. In our example, set up priority of tunnel 3  is 4 and R3  compares it against both hold priorities of established tunnels. R3 then concludes it has to drop t1 to accommodate t3 ( set up priority of tunnel3 is higher than the hold priority of tunnel1)

++++++++++++++++++++++++++++++++++++++++++++++++++++++

 

what is not cleared is how will router 3 behave if all the established tunnels have same hold priority i.e 4 and a request for a new tunnel i.e t3 comes with the set up priority of 4?

Not sure if R3 just randomly picks any established tunnel and drops it or there is some move involved process that R3 goes through to decide which tunnel gets dropped.

 

Lets hope somebody way smarter than me might chime in :)

 

Have a great weekend

 

 

Hello Friend,Good to know at

Hello Friend,

Good to know at-least there is one reason for dropping the tunnel, but as you said, if they comes with same hold priority then I believe it is all luck of the routers, or there should be nothing like routers are coming with same hold priority or there should be some other timers which are coming in play.

Let us see, how is it going on, let me also go through the book dear.

BR

Thanveer

Regards Thanveer "Everybody is genius. But if you judge a fish by its ability to climb a tree, it will live its whole life believing that it is a stupid."
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