RSVP TE FRR

Unanswered Question
Dec 13th, 2009

Hi,

Can we create only One Hop Tunnel , as Primary tunnel and multi-hop backup Tunnel for RSVP TE FRR to achieve fastes convergence.

Cannot my RSVP TE FRR Primary  Tunnel pass more than one hop...and achieve the same results..

r1----r2---r3---r4

|                    |

|                    |

|                    |

r5----r6----r7---r8

My source is connected to r1 & destination r4..

I plan to make a Primary multihop tunnel from   r1   to  r4 with FRR function, and thebackup r1--r5--r66--r7--r8...

Will the failure of anylink between r1, r2, r3, r4 trigger  FRR on Primary Tunnel ( assuming interface supports sub-50ms failure detection )

Regards,

Gaurav Prakash

I have this problem too.
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amit.bhagat Mon, 12/14/2009 - 03:00

Hi Gaurav,

There are two types of FRR- NHOP and NNHOP. Next-Hop (NHOP) is used to protect a link and Next Next-Hop (NNHOP) is used to protect the next-hop.

In your case, the PLR (Point of Local Repair) is R1-router. However, the MP (Merge Point) is unknown. Here, both (Primary and Backup) tunnels are two different tunnels and the second tunnel can be made to work as a Backup tunnel but only in case of NHOP.

If your destination is connected to R4-router, I think you should implement NNHOP- protecting R2-router with R3-router as the Merge Point. The Backup tunnel will be through R1-R5-R6-R7-R3.

Please let us know how you go with this.

HTH.

Regards,

Amit.

jcozzupoli Mon, 12/14/2009 - 03:45

Hi,

You would have to configure 2 TE Tunnels with Explicit paths as R1-R2-R3-R4 as primary and R1-R5-R6-R7-R8 as backup. To get superior fast convergence, I suggest you configure IS-IS as the IGP, as this is tweakable to easily acheive sub-50ms and even faster. I have implemented such solution and by tweaking the spf interval to the min (spf-interval 1 1 1) and also configured fast-flood to 2, this ensured extremely fast convergence and FRR failover and Fallback (even more important than failover). Of course configuring these tweaks, you'd have to ensure you have a very stable network, as such the implementation I ran was between 2 Data Centres with DWDM 10G links between them.

An Example Config for R1 would be as follows:

interface Tunnel100
ip unnumbered Loopback1
tunnel destination 44.44.44.44
tunnel mode mpls traffic-eng
tunnel mpls traffic-eng autoroute announce
tunnel mpls traffic-eng priority 0 0
tunnel mpls traffic-eng bandwidth 5000
tunnel mpls traffic-eng path-option 1 explicit name TE_DIRECT
tunnel mpls traffic-eng fast-reroute
no routing dynamic
!
interface Tunnel200
ip unnumbered Loopback1
tunnel destination 88.88.88.88
tunnel mode mpls traffic-eng
tunnel mpls traffic-eng priority 0 0
tunnel mpls traffic-eng bandwidth 5000
tunnel mpls traffic-eng path-option 1 explicit name TE_BACKUP
no routing dynamic
!

ip explicit-path name TE_DIRECT enable
next-address 2.2.2.1
next-address 3.3.3.2
next-address 4.4.4.3
!
ip explicit-path name TE_BACKUP enable
next-address 5.5.5.1
next-address 6.6.6.5
next-address 7.7.7.6
next-address 8.8.8.7

!

router isis
net 49.0001.1111.1111.1111.00
is-type level-2-only
metric-style wide
fast-flood 2
spf-interval 1 1 1
mpls traffic-eng router-id Loopback1
mpls traffic-eng level-2
!

HTH

Joe.

ulatif Tue, 12/15/2009 - 04:02

You have topology:

r1------r2-----r3-----r4

So you want to create a backup (FRR tunnel) such that a failure on the LSP between R1 -> R4 is protected by an FRR tunnel ? Is that your requirement?

FRR will not work in this scenario since you're not adhering to NHOP (link) or NNHOP (node) protection. PLR and MP are too far away

jcozzupoli Tue, 12/15/2009 - 14:31

Hi,

Yes I agree with Usman on this. With what you are asking isn't possible, I think you need to explain better what you are wanting to try to do and then we will be able to help you better.

Thanks,

Joe.

gauravprakash Fri, 12/18/2009 - 00:48

yes, what I want to achieve this with FRRin my below setup

Primary Tunnel :  Source & Destination are  3-4 hops away

Backup Tunnel :  Source & Destination are  6-7 hops away

I want sub-50ms protection , my interfaces of routers supports detection of failure in less than 50ms.

Is it possible ?

If Not , what else is the way

Thx to all ..

Rgds,

Gaurav Prakash

jcozzupoli Fri, 12/18/2009 - 19:59

Hi Gaurav,

Yes that is acheivable, if you look at the example configurations I gave you, and have your IGP tweaked (IS-IS for best resuls there), then having a backup tunnel with sub-50ms failover is very acheivable.

Thanks,

Joe.

ulatif Sun, 12/20/2009 - 14:29

No it won't work.

..unless you create more than one backup tunnels.

The maximum links you can protect with FRR = 2 and maximum nodes you can protect with FRR = 1

What you are asking may be possible with path-protection but it wont be FRR (so convergence won't be 50ms).

rgds,

Usman

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