Telecommunication Networks and Systemswajda/3Y_TNaS/TNaS_L6_MPLS...Concepts: •universal MPLS •label • Lecture scope Krzysztof Wajda , 20 15 traffic classification •labels,

Telecommunication

Networks and Systems

Krzysztof Wajda, 2015

Networks and Systems

MPLS

Fundamental concepts

Krzysztof Wajda

Department of Telecommunications, AGH-USTDecember, 2018

Outline

• Evolution towards MPLS

• Establishment of LSP and its consequences

• Label description

• Signalling in MPLS


• Signalling in MPLS

• RSVP for MPLS

Concepts:

• universal MPLS

• label

•

Lecture scope


• traffic classification

• labels, FECs, VPs

Evolution towardsMPLS


MPLS

• Too complicated ATM, complaints about ATM

• Necessity to increase speed of service in nodes (switching)

• Simple and implicit traffic engineering

Motivation to introduce MPLS


5

• Simple and implicit traffic engineering • Fundamental support for IP/ATM

interworking• MPLS as an idea of simplicity comparable

to IP and speed similar to ATM

Cell Switching Router (Toshiba)IP Switching (Ipsilon)Tag Switching (Cisco)ARIS (IBM)

Predecessors of MPS


6

IP = routing + forwardingATM = switching based on predefined two-

layer architecture (VP/VC) + advanced QoS methods

MPLS = switching based on flexible rules

IP, ATM, MPLS


7

MPLS = switching based on flexible rules aiming at definition of route for classified traffic stream

layer „3”

MPLS – protocol stack


8

layer „2,5”

layer „2”

• MPLS CP =

• IP CP + …

• … label distribution

MPLS – Control Plane


Labels


Labels

Signalling systems: CR-LDP,RSVP-TE,

other systems (?) with similar functionality of label distribution and path set-up,

MPLS – label distribution


11

of label distribution and path set-up,

No officicial support for CR-LDP from IETF, but works are still ongoing

MPLS

GMPLS

ATM

PNNI

MPLS – protocol positioning


12

CR-LDP RSVP-TE

GMPLS

CR-LDP RSVP-TE

ASON

CR-LDP RSVP-TE

FEC

Packet, Packet stream

MPLS – sequence of objects’ creation


13

• FEC = Forwarding Equivalence Class

• LSP = Label Switched Path

FEC

LSP

Label(s)

LSR – Label Switched Router, core node, label management (swapping) plus frame forwarding

E-LSR – Edge LSR, (also called LER)Traffic classification (FEC),

MPLS – switching nodes


14

Traffic classification (FEC), Label allocation, LSP initiation

„shim label”

0 1 2 3 4 5 6 7 8 91

0

1

1

1

2

1

3

1

4

1

5

1

6

1

7

1

8

1

9

2

0

2

1

2

2

2

3

2

4

2

5

2

6

2

7

2

8

2

9

3

0

3

1

Label Eksperi-mental

S TTL

MPLS – label


15

„shim label” Basic format used for IP/MPLS/Ethernet

An object, unambiguesly identifying flow in physical or logical interface

Label should be specific for interfaceLabel „5” within interface X is different that label „5” within

interface Y

Or labels can be general for given

MPLS – label description


16

Or labels can be general for given technology

Label „5” is fixed (not changed) regardless the interface

inside specific technological domain

Label value can be changed for each hop

LABEL DESIGNATION

0 IPv4 Explicit Null

1 Router Alert


0-15 Reserved

MPLS – label values


17


3 Implicit Null

4-14 Reserved for Future Use

15 OAM

16 - 220-1 Production Use

• Functions of LD in MPLS:

– FEC label binding

– distribution of bindings to neighbors

– Set-up and update of label swapping

MPLS – label distribution


– Set-up and update of label swapping tables in nodes

LSRs, LSPs


LSRs, LSPs

Basic definition is FEC (ForwardingEquivalence Class) – traffic differentiation:based on IP address,based on TE rules,based on „explicit route” concept,

LSP (VP) setup


20

based on „explicit route” concept,

After setting FEC there is label allocation.

• LSP – Label Switched Path• Often called „tunnel”• Always „unidirectional”• Classified as:

Dedicated p-p (point-to-point)

LSP


21

Dedicated p-p (point-to-point)Merging (combined)

MPLS – forwarding

Packet sent using IP

destination address

LER adds

Transfer using labels

„egress” node

removes label


22

LER adds

label to packet

LER: Label Edge Router

LSR: Label Switching Router

When sending packet alongside VP, only label is used, not destination IP address

VPs are inserted (nested) into other VP introducing scalability

Implemented by allowing more than 1 label in MPLS frame Creation of label stack

LSR forwards frame on the basis of top label (first

LSP stacking


23

LSR forwards frame on the basis of top label (first position in label stack)

Nesting is possible at any level

LSP stacking – an example

IP

Label introduced into packet

L2IP

Transfer using label L2

Label L1 Introduced into packet

Transfer using label L1


24

IP

L2IP L1

L2IP

Removal of external label Removal of

internal label

A B

C

Y

Z

RE

SV

Lab 1

00

200100

300100

100200

Label

Information

Base

Label Switched

Router

Y: to B Y: to C

Y: to Y

Label distribution


25

D

Y

RSVP-TE

X

W

PATH Lab_Req Y

Need label for

Destination Y

(LABEL_REQUEST

object in

PATH msg)

RESV Lab 300

RE

SV

Lab 1

00

Respond with a

label (receive)

(LABEL object

in RESV msg)

100200300100

100300

A B

C

Z

Y

100

450

100

MPLS – forwarding + protection


26

D

X

W MPLS Label

IP header

300100

Y

300

100200

50

150

ATM

MPLS

ATMSW

L

S

R

ATMSW

L

S

R

Resource management

MPLS over ATM„ships in the night”


27

ATMcontrol plane and MPLS work on the same hardware platform but they are separated

The node works simulatenously as MPLS LSR and ATM switch

Resource management– Space partitioning for VPI.VCI – TM

Bandwidth reservationCACqueueingshaping/policing

Bandwidth management

Summary

• Multiprotocol

• Scalability

• „Implicit” network engineering

• Importance of signalling systems


• Evolution towards GMPLS

• Yekhov, Rekhter, MPLS, Kluwer 2000• RFC3031, E. Rosen, A. Viswanathan, R. Callon. Multiprotocol Label Switching

Architecture. January 2001.

•

Bibliography


Architecture. January 2001.

• Lecture notes: http://www.kt.agh.edu.pl/~wajda/students/telecommunication-networks-and-

systems/

Thank you!


Documents

Telecommunication Networks and Systemswajda/3Y_TNaS/TNaS_L6_MPLS...Concepts: •universal MPLS •label • Lecture scope Krzysztof Wajda , 20 15 traffic classification •labels,