[j-nsp] Very basic question about MPLS and RSVP's place in the design

[Alexander Arseniev]

Hello,

Some answers:

A. bandwidth reservation is per outgoing interface that RSVP LSP takes 
and it is not truly global meaning that of course ingress LSR knows all 
the link bandwiths in given IGP domain but if there is "no bandwidth" 
signaled by upstream nodes, then ingress LSR router takes it at face 
value and Your LSP setup will fail. In fact, there could be BW attained 
by "repacking of existing LSPs to outgoing interfaces" in a different 
way but JUNOS does not do repacking. To achieve a truly global view of 
available and reserved BW, You need a centralised controller called 
Northstar but I digress.

B. To map different VRFs to different LSPs You'd need forwarding-table 
policy with "install-lsp" knob

http://www.gossamer-threads.com/lists/nsp/juniper/21830

Only equal-cost LSPs are considered in this policy. If Your two parallel 
LSP have different cost (by default they shouldn't as the default LSP 
cost is the minimum IGP cost to destination loopback) then You'd need to 
play with "no-install-to" and "install" knobs coupled with VRF nexthop 
rewriting to map different VRFs to different LSPs

https://www.juniper.net/documentation/en_US/junos13.3/topics/usage-guidelines/mpls-configuring-the-ingress-and-egress-router-addresses-for-lsps.html#id-95801

Thanks

Alex


On 26/10/2016 01:34, Scott Granados wrote:
> Hi, this is a very basic question at least I think it is, apologies for being so green in advance.
>
> I’m trying to wrap my head around MPLS and have built a small lab.  I understand how provider routers label switch packets and how provider edges use VRF instances and their distinguishers and targets to address each other.  Per the Juniper examples I have LDP and RSVP enabled on all the transit interfaces along with MPLS and obviously the correct interface families (MPLS) attached to the same transit interfaces.
>
> I then per the doc built a label switched path something like.
>
> set protocol MPLS label-switched-path r1-r4 to 10.0.0.4
> ;destination loopback of R4 which is acting as a PE
> I have an equal return to 1 built as well
> I also have a bandwidth reservation defined
> set protocol MPLS label-switched-path R1-R4 bandwidth 10M
> and a reverse reservation as well
>
> As I understand you build these relationships between the loopbacks.  My question is how does this relate to the VPN VRF entries on the provider edges?  Is this a global value that reserves 10 megabits between R1 and R4?  What if you want to reserve 10 megabits and 5 megabits between R1-R4-VRF1 <> R4-r1-vrf1  and r1-r4-vrf2 <> r4-r1-vrf2 where you have two matching sets of VRFs on the same PE pairs.  Is this possible or do I have the function of RSVP confused?
>
> Again sorry for the n00by question I’m just trying to figure out how all the pieces fit together.  If anyone has any reference pointers that might be  a good start that explains this I would be interested as well.  The Juniper documentation is quite good but I can’t figure this out via searching so far.  Any pointers would be most appreciated.
>
> Thank you
>
> Scott
>
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