Solved: One more question about RSVP-TE

agata.czekalska · ‎10-19-2009

Hello everybody!

How to enable rsvp to start signalling on interfaces. I found in cisco documantation something like that:

ip rsvp bandwidth [interface-kbps] [single-flow-kbps]

My question concerns necessity of setting bandwidth.

Best regards,

Agata

Peter Paluch · ‎10-20-2009

Hello Agata,

As far as I know, the RSVP is started on interfaces as soon as MPLS-TE is enabled on them and in the routing protocol. You should not need to use any "ip rsvp bandwidth" command to have the MPLS-TE running. When I teach about the MPLS-TE, I teach the most simple configuration without using any "ip rsvp" commands and it works.

Make sure that your MPLS-TE support is correctly turned on exactly as Giuseppe has suggested. Also verify that individual routers are recognized in the "show mpls traffic-eng topology" output.

Best regards,

Peter

View solution in original post

Giuseppe Larosa · ‎10-19-2009

Hello Agata,

see this document

http://www.cisco.com/en/US/tech/tk436/tk428/technologies_configuration_example09186a0080093fd0.shtml#configfiles

you need on physical interfaces:

mpls ip

mpls traffic-eng tunnels

+

ip rsvp bandwidth value1 value2

also on the routing protocol you need to enable MPLS TE extensions, to define the MPLS TE router-id;

first value is the total BW resources on the link, second value is max BW that can be used by a single flow / single tunnel

MPLS TE like MPLS LDPs are unidirectional and resources are consumed per direction.

Also notice that bandwidth value on an MPLS TE does not imply a policer: that is on an MPLS TE with bw 5 Mbps you can put 20 or more Mbps of traffic.

Call Admission Control is performed at tunnel setup.

This unless using auto-bandwidth.

Hope to help

Giuseppe

agata.czekalska · ‎10-19-2009

Hi Giuseppe and other Folks!!!

The problem is a little bit different.

I'm under test implementation of Regular Path Protection (Cisco calls it like taht). Topology consists of one Cisco Catalyst 6500 series switch and four MRV boxes. I have a ring with five nodes.

Ring goes like that: Cat6500-MRV1-MRV3-MRV2-MRV4-Cat6500.

What I want to do is use MPLS TE feature: path protection.

I set up one VC between two MRV switches(MRV3 and MRV 4, so MRV2 is between them). I configured a trunk (which is a TE LSP according to MRV paper). I have also created two rsvp paths, one of wchich plays primary role. The second one acts as a backup path. Both are strict at the moment.

I can now transfer some traffic through created VC, but to simulate the backup path I need to anable rsvp protocol on Catalyst 6500 as far as secondary path goes through the Cisco device.

Question is: how to make Cisco switch start signalling RSVP messages?

As far as I know we create tunnels at the end devices. In my configration Cisco is a transit device. If I issue ip rsvp on interfaces it does not still exchange RSVP messages with other devices.

As always gratful for answers, comments, ideas.

Best regards,

Agata Czekalska

Technical University of Lodz

Peter Paluch · ‎10-20-2009

Hello Agata,

As far as I know, the RSVP is started on interfaces as soon as MPLS-TE is enabled on them and in the routing protocol. You should not need to use any "ip rsvp bandwidth" command to have the MPLS-TE running. When I teach about the MPLS-TE, I teach the most simple configuration without using any "ip rsvp" commands and it works.

Make sure that your MPLS-TE support is correctly turned on exactly as Giuseppe has suggested. Also verify that individual routers are recognized in the "show mpls traffic-eng topology" output.

Best regards,

Peter

Giuseppe Larosa · ‎10-20-2009

Hello Agata,

>> Question is: how to make Cisco switch start signalling RSVP messages?

you need to create a tunnel to have RSVP to start its activity.

my understanding is that RSVP has no hellos concept.

when you create the tunnel messages for setting up the tunnel startup.

Peter:

ip rsvp bandwidth is still needed to be able to accept a new tunnel setup.

Hope to help

Giuseppe

Peter Paluch · ‎10-21-2009

Hello Giuseppe,

Regarding the RSVP Hellos - the original specification in RFC 2205 indeed does not specify any hello mechanism. For MPLS-TE, the RFC 3209 specifies an optional Hello mechanism (it is not mandated than any implementation uses it).

Regarding the "ip rsvp bandwidth" command: I am completely sure that I do not need to use it if I do not configure the bandwidth requirement of a tunnel. I have verified it right now both with explicit and dynamic path option. Of course, no bandwidth guarantees can then be provided. Certainly, if a tunnel bandwidth requirement is given by the command "tunnel mpls traffic-eng bandwidth", then it is absolutely necessary to use the "ip rsvp bandwidth" command as well, otherwise the reservable and available bandwidth on each MPLS-TE-enabled interface is 0. But if you just need to specify explicit paths without bandwidth requirements than you can happily go without using the "ip rsvp bandwidth" command.

Best regards,

Peter

Giuseppe Larosa · ‎10-21-2009

Hello Peter,

I always used a small (1 Mbps) bandwidth setup or auto-bandwidth in my tunnels.

MPLS TE CAC is far less smart then ATM CAC because (at least some years ago) it couldn't take in account real traffic volume using the tunnel (even with auto-BW you can provide a max value if I remember correctly).

It is funny to discover that missing statement is like 0 BW request.

About RSVP activity: I just tried to point out that is different then a standard routing protocol that is you can capture RSVP messages but they relate to configured tunnels if we start with a network that is ready for MPLS TE but with no tunnel configured and we try to capture signalling protocols we shouldn't see RSVP messages.

Hope to help

Giuseppe