MPLS cisco QOS VPN full 03 mpls te toi

MPLS TE TOI


Course Number
Presentation_ID

© 2001, Cisco Systems, Inc.

1


Agenda

• How MPLS TE works
• What Code Is MPLS TE In?
• Platform Issues in Implementation
• Lab Demo - config

Presentation_ID

© 2001, Cisco Systems, Inc.

2


How MPLS TE Works

• Prerequisites
• How MPLS-TE Works
• Basic Configuration
• Knobs!

Knobs!

Knobs!

• Deploying and Designing

Presentation_ID

© 2001, Cisco Systems, Inc.

3


Prerequisites

You should already understand…
• How to configure a Cisco router
• Basic MPLS concepts like
push/pop/swap, EXP, and LFIB
• How a link-state routing protocol
works
• Basic QoS mechanisms like MDRR and LLQ

Presentation_ID

© 2001, Cisco Systems, Inc.

4

Agenda

• Prerequisites
• How MPLS-TE Works
• Basic Configuration
• Knobs!

Knobs!

Knobs!

• Deploying and Desiginig

Presentation_ID

© 2001, Cisco Systems, Inc.

5


How MPLS-TE Works

• How MPLS-TE Works
-What good is MPLS-TE?
-Information Distribution
-Path Calculation
-Path Setup
-Forwarding Traffic Down A Tunnel

Presentation_ID

© 2001, Cisco Systems, Inc.

6


What Good Is MPLS-TE?

•

There are two kinds of networks

1. Those that have plenty of bandwidth
everywhere
2. Those with congestion in some places, but
not in others
•

Presentation_ID

The first kind always evolve into the second kind!

© 2001, Cisco Systems, Inc.

7


What Good Is MPLS-TE?

•

MPLS-TE introduces a 3rd kind:
1.

Those that have plenty of bandwidth everywhere

2.

Those with congestion in some places, but not in others

3. Those that use all of their bandwidth to its
maximum efficiency, regardless of shortestpath routing!

Presentation_ID

© 2001, Cisco Systems, Inc.

8


What Good Is MPLS-TE?
What is MPLS-TE? What is it not?
Multi
Protocol
Label
Switching Traffic
Engineering

Magic

Problem-solving
Labor
Substitute which is
Totally
Effortless

This stuff takes work, but it’s worth it!!!

Presentation_ID

© 2001, Cisco Systems, Inc.

9


Information Distribution

• You need a link-state protocol as your IGP

IS-IS or OSPF
• Link-state requirement is only for MPLS-TE!

Not a requirement for VPNs, etc!

Presentation_ID

© 2001, Cisco Systems, Inc.

10

Need for a Link-State Protocol

•

Why do I need a link-state protocol?

1. To make sure info gets flooded
2. To build a picture of the entire network

Presentation_ID

© 2001, Cisco Systems, Inc.

11


Need for a Link-State Protocol

Consider the following network:
- All links have a cost of 10
- RtrA’s path to RtrE is A->B->E, cost 20
- All traffic from A to {E,F,G} goes A->B->E

RtrB

RtrF

RtrA

RtrE
RtrG

RtrC
Presentation_ID

© 2001, Cisco Systems, Inc.

RtrD
12


What a DV Protocol Sees
Node Next-Hop

Cost

B

B

10

C

C

10

D

C

20

E

B

20

F

B

30

G

B

30

• RtrA doesn’t see all
the links
• RtrA only knows about
the shortest path
• This is by design
RtrB

RtrF

RtrA

RtrE
RtrG

RtrC
Presentation_ID

© 2001, Cisco Systems, Inc.

RtrD
13


What a LS Protocol Sees
• RtrA sees all links
Node Next-Hop

Cost

B

B

10

C

C

10

D

C

20

E

B

20

F

B

30

G

B

30

• RtrA only computes
the shortest path

• Routing table
doesn’t change
RtrB

RtrF

RtrA

RtrE
RtrG

RtrC
Presentation_ID

© 2001, Cisco Systems, Inc.

RtrD
14


The Problem With Shortest-Path
Node Next-Hop

Cost

B

B

10

C

C

10

D

C

20

E

B

20

F

B

30

G

B

30

• Some links are DS3, some
are OC3

• RtrA has 40Mb of traffic for
RtrF, 40Mb of traffic for RtrG
• Massive (44%) packet loss at
RtrB->RtrE!
• Changing to A->C->D->E
won’t help

RtrB
RtrA

RtrF

OC3
DS3

OC3

RtrG
DS3

RtrC
Presentation_ID

RtrE OC3

© 2001, Cisco Systems, Inc.

DS3

OC3

RtrD
15


What MPLS-TE Addrs
Node Next-Hop

Cost

B

B

10

C

C

10

D

C

20

E

B

20

F

Tunnel0

30

G

Tunnel1

30

• RtrA sees all links
• RtrA computes paths on
properties other than
just shortest cost
• No congestion!
RtrB

RtrA

RtrF

OC3
DS3

OC3

RtrG
DS3

RtrC
Presentation_ID

RtrE OC3

© 2001, Cisco Systems, Inc.

DS3

OC3

RtrD
16


How MPLS-TE Works

• How MPLS-TE Works
-What good is MPLS-TE?
-Information Distribution
-Path Calculation

-Path Setup
-Forwarding Traffic Down A Tunnel

Presentation_ID

© 2001, Cisco Systems, Inc.

17


Information Distribution

• OSPF

-Uses Type 10 (Opaque Area-Local) LSAs
-See draft-katz-yeung-ospf-traffic

Presentation_ID

© 2001, Cisco Systems, Inc.

18


Information Distribution

• IS-IS

-Uses Type 22 TLVs
-See draft-ietf-isis-traffic

Presentation_ID

© 2001, Cisco Systems, Inc.

19


Information Distribution

• IS-IS and OSPF propagate the same
information!
-Link identification
-TE Metric
-Bandwidth info (max physical, max reservable,
available per-class)
-Attribute flags

Presentation_ID

© 2001, Cisco Systems, Inc.

20


Information Distribution

• TE flooding is local to a single {area|level}
• Inter-{area|level} TE harder, but possible (think PNNI)

Presentation_ID

© 2001, Cisco Systems, Inc.

21


How MPLS-TE Works

• How MPLS-TE Works
-What good is MPLS-TE?
-Information Distribution
-Path Calculation
-Path Setup
-Forwarding Traffic Down A Tunnel

Presentation_ID

© 2001, Cisco Systems, Inc.

22


Path Calculation

• Modified Dijkstra at tunnel head-end
• Often referred to as CSPF

Constrained SPF
• …or PCALC (path calculation)

Presentation_ID

© 2001, Cisco Systems, Inc.

23


Path Calculation
• Normal SPF – find
shortest path
across all links

“what’s the
shortest path to
all routers?”

• See Perlman (2nd
ed), Moy, etc. for
explanation of SPF
RtrB

RtrF

RtrA

RtrE
RtrG

RtrC

Presentation_ID

© 2001, Cisco Systems, Inc.

RtrD
24


Path Calculation

“what’s the
shortest path to
all routers?”

• Normal SPF – find
shortest path
across all links
• See Perlman (2nd
ed), Moy, etc. for
explanation of SPF

RtrA

Presentation_ID

© 2001, Cisco Systems, Inc.

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