MPLS TE tunnel Bandwidth and ip rsvp bandwidth

[mariogu2004]

I have some questions about how to reserve bandwidth in MPLS TE enviorment.

1. We must IP RSVP bandwidth in all concern interface in MPLS TE enviroment, right?

2. What's the goal of ip rsvp bandwidth?

3. Tunnel MPLS traffic-enginerring bandwitdh XXX, the command define flow bandwidth initiated by head-end, if sending more than XXX flow, how does it work? Drop excessive packet in the flow?

Any point is welcome! Thanks!

[mheusinger · Accepted solution]

Hello,

A1) Right.

A2) With "ip rsvp bandwidth" one specifies, how much bandwidth on an interface can be booked by MPLS TE tunnels.

A3) The most misuderstood feature is probably MPLS TE. It is a pure Control plane feature. So there is nocheck or comparison of booked bandwidth versus real bandwidth used.

You can configure a MPLS TE tunnel with 1 kbps ("tunnel mpls traffic-engineering 1") and send 10 Gbps down the path and NO action will be taken.

In case there is an interface in the path, which is overloaded, then packets will be treated regardless of having a tunnel label or not.

You might ask: what´s the point of MPLS TE then, if I can´t give bandwidth guarantees with it? Answer: MPLS TE allows for a more complex and controlable path selection in the MPLS environment. In addition features like Fast ReRoute (FRR) are interesting.

Hope this helps! PLease rate all posts.

Regards, Martin

[mheusinger]

Hello,

just today I found some time to read RFCs. and found:

4124 Protocol Extensions for Support of Diffserv-aware MPLS Traffic Engineering. F. Le Faucheur, Ed.. June 2005. (Format: TXT=79265 bytes) (Status: PROPOSED STANDARD)

4125 Maximum Allocation Bandwidth Constraints Model for Diffserv-aware MPLS Traffic Engineering. F. Le Faucheur, W. Lai. June 2005. (Format: TXT=22585 bytes) (Status: EXPERIMENTAL)

4126 Max Allocation with Reservation Bandwidth Constraints Model for Diffserv-aware MPLS Traffic Engineering & Performance Comparisons. J. Ash. June 2005. (Format: TXT=51232 bytes) (Status: EXPERIMENTAL)

4127 Russian Dolls Bandwidth Constraints Model for Diffserv-aware MPLS Traffic Engineering. F. Le Faucheur, Ed.. June 2005. (Format: TXT=23694 bytes) (Status: EXPERIMENTAL)

4128 Bandwidth Constraints Models for Differentiated Services (Diffserv)-aware MPLS Traffic Engineering: Performance Evaluation. W. Lai. June 2005. (Format: TXT=58691, PDF=201138 bytes) (Status: INFORMATIONAL)

4201 Link Bundling in MPLS Traffic Engineering (TE). K. Kompella, Y. Rekhter, L. Berger. October 2005. (Format: TXT=27033 bytes) (Updates RFC3471, RFC3472, RFC3473) (Status: PROPOSED STANDARD)

Basically these standards allow to combine congestion management and MPLS TE. The standard says a router "may allocate ressources" based on the MPLS TE reservations.

So MPLS DiffServ-aware TE can deliver both TE and QoS.

Regards, Martin

[jamesma01]

Hi,

reading this answer, I am quite surprised that Tunnel MPLS traffic-enginerring bandwitdh XXX does not guarantee any bandwidth.

Although it seems Martin was quite sure about it, I am wondering if anybody can confirm it?

Thanks,