What is MPLS TE?

Answered Question
Oct 20th, 2009

I'm having a real difficult time understanding MPLS TE? Does anyone have a link or technotes that explains TE?

Thanks in advance.

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Correct Answer by Jon Marshall about 7 years 2 months ago

David

Another option is to look at Dynamips which allows you to emulate 7200 routers and this would then allow you to lab up MPLS-TE.

http://www.ipflow.utc.fr/index.php/Cisco_7200_Simulator

Jon

Correct Answer by Giuseppe Larosa about 7 years 2 months ago

Hello David,

thanks I thought to focus on conceptual difference with normal IP routing.

the tunnel is a logical interface defined only on originator node.

the tunnel is unidirectional (this is different from GRE tunnels) and works only in outbound direction.

the destination of tunnel 1 can be the originator of tunnel 2 with destination = originator of tunnel 1

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;

Having OSPF is a good starting point because only OSPF and IS-IS support MPLS TE.

Hope to help

Giuseppe

Correct Answer by Giuseppe Larosa about 7 years 3 months ago

Hello David,

to keep it simple

MPLS TE can create pre-established paths like FR PVCs or ATM PVCs over IPv4/MPLS networks.

This creates a big difference with normal IP routing:

in normal IP routing the packet is examined and routed at each router next-hop.

if I want to divert some traffic on an alternate path that spans on three routers with IP routing I need:

a PBR rule at each router hop to enforce the packets on the intended path otherwise traffic is sent along lowest cost path.

With MPLS TE a pipe is created and device at the beginning on the pipe places traffic into it.

devices in the middle don't need any config change (no PBR on intermediate devices)they just switch the external MPLS labels

this can be done because in configuring the MPLS TE tunnel I can provide a so called explicit path that lists the devices the tunnel should go through.

each MPLS TE router can be:

an originator of tunnels

a final destination of tunnels

a device in the middle of other tunnels

Hope to help

Giuseppe

Correct Answer by Jon Marshall about 7 years 3 months ago

David

What exactly are you struggling with.

At a very high-level MPLS-TE allows you control which path traffic takes so you can send higher priority traffic over one path and less important traffic over another.

It also allows you reserve resources within the MPLS network so that if you want to send traffic over a certain path but that path must meet certain conditions in terms of performance, you can ensure that those conditions are met before sending the traffic.

Jon

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davidhuynh5 Wed, 10/21/2009 - 08:50

That was the article that I read, which confused me. Sorry..I'm really new to the technology...anything for a dummy like myself?

Correct Answer
Jon Marshall Wed, 10/21/2009 - 08:56

David

What exactly are you struggling with.

At a very high-level MPLS-TE allows you control which path traffic takes so you can send higher priority traffic over one path and less important traffic over another.

It also allows you reserve resources within the MPLS network so that if you want to send traffic over a certain path but that path must meet certain conditions in terms of performance, you can ensure that those conditions are met before sending the traffic.

Jon

Correct Answer
Giuseppe Larosa Wed, 10/21/2009 - 09:20

Hello David,

to keep it simple

MPLS TE can create pre-established paths like FR PVCs or ATM PVCs over IPv4/MPLS networks.

This creates a big difference with normal IP routing:

in normal IP routing the packet is examined and routed at each router next-hop.

if I want to divert some traffic on an alternate path that spans on three routers with IP routing I need:

a PBR rule at each router hop to enforce the packets on the intended path otherwise traffic is sent along lowest cost path.

With MPLS TE a pipe is created and device at the beginning on the pipe places traffic into it.

devices in the middle don't need any config change (no PBR on intermediate devices)they just switch the external MPLS labels

this can be done because in configuring the MPLS TE tunnel I can provide a so called explicit path that lists the devices the tunnel should go through.

each MPLS TE router can be:

an originator of tunnels

a final destination of tunnels

a device in the middle of other tunnels

Hope to help

Giuseppe

davidhuynh5 Wed, 10/21/2009 - 16:03

Thanks for the easy to understand explanation. When you guys say tunnel, are you referring to a MPLS GRE Tunnel or something different? Would it require a big change on our current OSPF network? Do you have any sample configuration for my simple mind? Thanks again.

Correct Answer
Giuseppe Larosa Wed, 10/21/2009 - 22:27

Hello David,

thanks I thought to focus on conceptual difference with normal IP routing.

the tunnel is a logical interface defined only on originator node.

the tunnel is unidirectional (this is different from GRE tunnels) and works only in outbound direction.

the destination of tunnel 1 can be the originator of tunnel 2 with destination = originator of tunnel 1

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;

Having OSPF is a good starting point because only OSPF and IS-IS support MPLS TE.

Hope to help

Giuseppe

davidhuynh5 Thu, 10/22/2009 - 02:16

One last question, can I lab up an MPLS-TE network using just 3550/60 swicthes?

The article says I need 76xx or 72xx, which are too expensive for a personal lab. Thanks.

Giuseppe Larosa Thu, 10/22/2009 - 02:31

Hello David,

you would need Cisco routers or C3750 ME to test it.

MPLS features are not supported on switches like C3550 or C3560

Hope to help

Giuseppe

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