MPLS

1
MPLS
Whats in it for Research Education Networks?

• John Jamison
• University of Illinois at Chicago
• November 17, 2000

2
Juniper Networks Product Family
Sept 2000 M10
Sept 2000 M5
Mar 2000 M160
Nov 1999 M20
Sept 1998 M40
3
Juniper NetworksResearch and Education Customers

• University of Illinois NCSA (National Center
  for Supercomputing Applications)
• University of California, San Diego - SDSC (San
  Diego Supercomputer Center)
• University of Southern California, Information
  Sciences Institute
• Indiana University
• Stanford University
• University of California, Davis
• California Institute of Technology
• North Carolina State University
• University of Alaska
• University of Hiroshima, Japan
• Korea Telcom Research Lab
• ETRI (Electronic and Transmission Research
  Institute), Korea

• MCI Worldcom vBNS/vBNS
• Department of Energy ESnet
• DANTE - TEN-155 (Pan-European Research
  Education Backbone)
• NYSERNet New York State Education Research
  Network
• Georgia Tech SOX GigaPoP
• University of Washington Pacific/Northwest
  GigaPoP
• STAR TAP (International Research Education
  Network Meet Point)
• APAN (Asia Pacific Advanced Network) Consortium
• NOAA (National Oceanographic and Atmospheric
  Administration)
• NASA Goddard Space Flight Center
• NIH (National Institutes of Health)
• DoD (Department of Defense)
• US Army Engineer Research andDevelopment Center

4
Original Agenda

• MPLS Fundamentals
• Traffic Engineering
• Constraint-Based Routing
• Refreshment Break
• Virtual Private Networks
• Optical Applications for MPLS Signaling
  (GMPLS/MP?S)
• Juniper Networks Solutions
• Questions and Comments

5
Our Agenda

• MPLS Overview
• Traffic Engineering
• VPNs

6
What are we missing out on?

• A bunch of pure marketing slides
• A bunch of filler slides
• Slides with content that is of interest mainly to
  ISPs
• Here is how you can use MPLS to bring in more
  revenue, offer different services, etc.
• Some Details of MPLS Signaling Protocols and RFC
  2547 VPNs
• You can (and should) only cover so much in one
  talk
• Some MP(Lambda)S Details
• Seems too much like slide ware right now

7
What are we gaining?

• Besides being spared marketing and ISP centric
  stuff
• We will see some examples from networks and
  applications we are familiar with
• We will save some time and cover almost as much
  information

8
Why Is MPLSan Important Technology?

• Fully integrates IP routing L2 switching
• Leverages existing IP infrastructures
• Optimizes IP networks by facilitatingtraffic
  engineering
• Enables multi-service networking
• Seamlessly integrates private and public networks
  
• The natural choice for exploring new and
  richerIP service offerings
• Dynamic optical bandwidth provisioning

9
What Is MPLS?

• IETF Working Group chartered in spring 1997
• IETF solution to support multi-layer switching
• IP Switching (Ipsilon/Nokia)
• Tag Switching (Cisco)
• IP Navigator (Cascade/Ascend/Lucent)
• ARIS (IBM)
• Objectives
• Enhance performance and scalability of IP routing
• Facilitate explicit routing and traffic
  engineering
• Separate control (routing) from the forwarding
  mechanismso each can be modified independently
• Develop a single forwarding algorithm to support
  a widerange of routing and switching
  functionality

10
MPLS Terminology

• Label
• Short, fixed-length packet identifier
• Unstructured
• Link local significance
• Forwarding Equivalence Class (FEC)
• Stream/flow of IP packets
• Forwarded over the same path
• Treated in the same manner
• Mapped to the same label
• FEC/label binding mechanism
• Currently based on destination IP address prefix
• Future mappings based on SP-defined policy

11
MPLS Terminology
Connection Table
In (port, label)
Out (port, label)
Label Operation
Port 1
Port 2
Swap
Swap
Swap
Port 3
Port 4
Swap

• Label Swapping
• Connection table maintains mappings
• Exact match lookup
• Input (port, label) determines
• Label operation
• Output (port, label)
• Same forwarding algorithm used in Frame Relay and
  ATM

12
MPLS Terminology
New York
San Francisco
LSP

• Label-Switched Path (LSP)
• Simplex L2 tunnel across a network
• Concatenation of one or more label switched hops
• Analogous to an ATM or Frame Relay PVC

13
MPLS Terminology
LSR
New York
LSR
LSR
San Francisco
LSR
LSP

• Label-Switching Router (LSR)
• Forwards MPLS packets using label-switching
• Capable of forwarding native IP packets
• Executes one or more IP routing protocols
• Participates in MPLS control protocols
• Analogous to an ATM or Frame Relay Switch (that
  also knows about IP)

14
MPLS Terminology
Egress LSR
Ingress LSR
New York
Transit LSR
San Francisco
Transit LSR
LSP

• Ingress LSR (head-end LSR)
• Examines inbound IP packets and assigns them to
  an FEC
• Generates MPLS header and assigns initial label
• Transit LSR
• Forwards MPLS packets using label swapping
• Egress LSR (tail-end LSR)
• Removes the MPLS header

15
MPLS Header
IP Packet
L2 Header
MPLS Header
32-bits

• Fields
• Label
• Experimental (CoS)
• Stacking bit
• Time to live
• IP packet is encapsulated by ingress LSR
• IP packet is de-encapsulated by egress LSR

16
IP Packet Forwarding Example
134.5.6.1
Routing Table
Destination
Next Hop
134.5.1.5
134.5/16
134.5.6.1
200.3.2/24
200.3.2.1
2
12.29.31.1
12.29.31.4
3
5
Routing Table
Destination
Next Hop
12.29.31.5
12.29.31.9
134.5/16
12.29.31.5
200.3.2/24
12.29.31.5
200.3.2.1
Routing Table
Routing Table
200.3.2.7
Destination
Next Hop
Destination
Next Hop
134.5/16
12.29.31.5
134.5/16
12.29.31.5
200.3.2/24
12.29.31.4
200.3.2/24
12.29.31.9
17
MPLS Forwarding Example
MPLS Table
134.5.6.1
In
Out
(2, 84)
(6, 0)
134.5.1.5
2
6
Egress Routing Table
Destination
Next Hop
2
134.5/16
134.5.6.1
3
200.3.2/24
200.3.2.1
1
2
3
5
Ingress Routing Table
Destination
Next Hop
134.5/16
(2, 84)
200.3.2/24
(3, 99)
MPLS Table
MPLS Table
200.3.2.7
200.3.2.1
In
Out
In
Out
(1, 99)
(2, 56)
(3, 56)
(5, 0)
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How Is Traffic Mappedto an LSP?
AS 45
AS 63
134.5.1.5
BGP
BGP
E-BGP peers
E-BGP peers
AS 77 Transit SP
I-BGP peers
BGP
BGP
LSP 32
Egress LSR
Ingress LSR
Routing Table
134.5/16
LSP 32

• Map LSP to the BGP next hop
• FEC all BGP destinations reachable via egress
  LSR

19
How are LSPs Set Up?
EgressLSR
IngressLSR
LSP

• Two approaches
• Manual Configuration
• Using a Signaling Protocol

20
MPLS Signaling Protocols

• The IETF MPLS architecture does not assumea
  single label distribution protocol
• LDP
• Executes hop-by-hop
• Selects same physical path as IGP
• Does not support traffic engineering
• RSVP
• Easily extensible for explicit routes and label
  distribution
• Deployed by providers in production networks
• CR-LDP
• Extends LDP to support explicit routes
• Functionally identical to RSVP
• Not deployed

21
How Is the LSP PhysicalPath Determined?
EgressLSR
IngressLSR
LSP

• Two approaches
• Offline path calculation (in house or 3rd party
  tools)
• Online path calculation (constraint-based
  routing)
• A hybrid approach may be used

22
Offline Path Calculation

• Simultaneously considers
• All link resource constraints
• All ingress to egresstraffic trunks
• Benefits
• Similar to mechanisms usedin overlay networks
• Global resource optimization
• Predictable LSP placement
• Stability
• Decision support system
• In-house and third-party tools

23
Offline Path Calculation
R6
R9
EgressLSR
R2
R1
IngressLSR
R4
R7
R8
R3
R5
Explicit route R1, R4, R8, R9
LSP

• Input to offline path calculation utility
• Ingress and egress points
• Physical topology
• Traffic matrix (statistics about city - router
  pairs)
• Output
• Set of physical paths, each expressedas an
  explicit route

24
Explicit Routes Example 1
R6
R9
EgressLSR
R2
R1
IngressLSR
R4
R7
R8
R3
R5

• LSP from R1 to R9
• Partial explicit route
• loose R8, strict R9
• LSP physical path
• R1 to R8 follow IGP path
• R8 to R9 directly connected

25
Explicit Routes Example 2
R6
R9
EgressLSR
R2
R1
IngressLSR
R4
R7
R8
R3
R5

• LSP from R1 to R9
• Full explicit route
• strict R3, strict R4, strict R7, strict R9
• LSP physical path
• R1 to R3 directly connected
• R3 to R4 directly connected
• R4 to R7 directly connected
• R7 to R9 directly connected

26
Constraint-Based Routing
EgressLSR
IngressLSR
User defined LSP constraints

• Online LSP path calculation
• Operator configures LSP constraints at ingress
  LSR
• Bandwidth reservation
• Include or exclude a specific link(s)
• Include specific node traversal(s)
• Network actively participates in selecting an
  LSPpath that meets the constraints

27
Constraint-Based Routing

• Thirty-two named groups, 0 through 31
• Groups assigned to interfaces

Silver
Gold
San Francisco
Bronze
28
Constraint-Based Routing

• Choose the path from A to I using
• admin group
• include gold sliver

Copper
Gold
Copper
Bronze
Bronze
Bronze
Silver
Copper
Bronze
Copper
Copper
Gold
6
Copper
Gold
29
Constraint-Based Routing

• A-C-F-G-I uses only gold or silver links

B
G
Copper
Gold
I
Copper
Bronze
Bronze
6
Bronze
Silver
E
A
Copper
1
Bronze
Copper
Copper
2
D
Gold
H
Copper
Gold
C
F
30
Constraint-Based Routing Example 1
Seattle
Chicago
New York
San Francisco
Kansas City
Los Angeles
Atlanta
label-switched-path SF_to_NY
to New_York from
San_Francisco admin-group
exclude green cspf
Dallas
31
Constraint-Based Routing Example 2
label-switched-path madrid_to_stockholm
to Stockholm
from Madrid admin-group
include red, green cspf
Stockholm
London
Paris
Munich
Geneva
Madrid
Rome
31
32
Other Neat MPLS Stuff

• Secondary LSPs
• Fast Reroute
• Label Stacking
• GMPLS

33
MPLS Secondary LSPs
New York Data Center
San Francisco Data Center

• Standard LSP failover
• Failure signaledto ingress LSR
• Calculate signal new LSP
• Reroute traffic to new LSP

• Standby Secondary LSP
• Pre-established LSP
• Sub-second failover

34
MPLS Fast Reroute
New York Data Center
San Francisco Data Center

• Ingress signals fast reroute during LSP setup
• Each LSR computes a detour path(with same
  constraints)
• Supports failover in 100s of ms

35
MPLS Label Stacking
Trunk LSP
LSP 1
LSP 2

• A label stack is an ordered set of labels
• Each LSR processes the top label
• Applications
• Routing hierarchy
• Aggregate individual LSPs into a trunk LSP
• VPNs

36
MPLS Label Stack Example 1
Trunk LSP
MPLS Table
MPLS Table
MPLS Table
MPLS Table
In
Out
In
Out
In
Out
In
Out
(2, 18)
(5, Pop)
(4, 25)
(2, 56)
(5, 42)
(6, 18)
(1, 25)
(2, Push 42)
(4, 35)
(5, 17)
(3, 35)
(2, Push 42)
37
MPLS Label Stack Example 2
Trunk LSP
MPLS Table
MPLS Table
MPLS Table
MPLS Table
In
Out
In
Out
In
Out
In
Out
(2, 18)
(5, Pop)
(4, 25)
(2, 56)
(5, 42)
(6, 18)
(1, 25)
(2, Push 42)
(4, 35)
(5, 17)
(3, 35)
(2, Push 42)
38
Label Stacking allows you to Reduce the Number of
LSPs
LSP 1
LSP 1
LSP 2
LSP 2
LSP Trunk
LSP Trunk of Trunks
LSP 3
LSP 3
LSP Trunk
LSP 4
LSP 4

• Label stacking to create a hierarchy of LSP trunks

39
Generalized MPLS (GMPLS)Formally known as
MPL(amda)S
IP Service (Routers)
Optical Core
Optical Transport (OXCs, WDMs)

• Reduce complexity
• Reduce cost
• Router subsumes functions performed by other
  layers
• Fast router interfaces eliminate the need for
  MUXs
• MPLS replaces ATM/FR for traffic engineering
• MPLS fast reroute obviates SONET APS restoration
• Dynamic provisioning of optical bandwidth is
  required for growth and innovative service
  creation

40
GMPLS LSP Hierarchy
LSC Cloud
TDM Cloud
PSC Cloud
LSC Cloud
TDM Cloud
PSC Cloud
FSC Cloud
Fiber 1
Bundle
Fiber n
FA-PSC
FA-TDM
FA-LSC
Explicit Label LSPs
Time-slot LSPs
Explicit Label LSPs
Time-slot LSPs
l LSPs
l LSPs
Fiber LSPs
(multiplex low-order LSPs)
(demultiplex low-order LSPs)

• Nesting LSPs enhances system scalability
• LSPs always start and terminate on similar
  interface types
• LSP interface hierarchy
• Packet Switch Capable (PSC) Lowest
• Time Division Multiplexing Capable (TDM)
• Lambda Switch Capable (LSC)
• Fiber Switch Capable (FSC) Highest

41
AGENDA

• MPLS Overview
• Traffic Engineering
• VPNs

42
What Is Traffic Engineering?
Source
Destination
Traffic Engineering
Layer 3 Routing

• Ability to control traffic flows in the network
• Optimize available resources
• Move traffic from IGP path to less congested path

43
Brief History

• Early 1990s
• Internet core was connected with T1 and T3 links
  between routers
• Only a handful of routers and links to manage and
  configure
• Humans could do the work manually
• Metric-based traffic control was sufficient

44
Metric-Based Traffic Engineering

• Traffic sent to A or B follows path with lowest
  metrics

1
1
A
B
1
2
C
45
Metric-BasedTraffic Engineering

• Drawbacks
• Redirecting traffic flow to A via C causes
  traffic for B to move also!
• Some links become underutilized or overutilized

1
4
A
B
1
2
C
46
Metric-BasedTraffic Engineering

• Drawbacks
• Complexity made metric control tricky
• Adjusting one metric might destabilize network

47
Discomfort Grows

• Mid 1990s
• ISPs became uncomfortable with size of Internet
  core
• Large growth spurt imminent
• Routers too slow
• Metric engineering too complex
• IGP routing calculation was topology driven, not
  traffic driven
• Router based cores lacked predictability

48
Overlay Networks are Born

• ATM switches offered performance and predictable
  behavior
• ISPs created overlay networks that presented a
  virtual topology to the edge routers in their
  network
• Using ATM virtual circuits, the virtual network
  could be reengineered without changing the
  physical network
• Benefits
• Full traffic control
• Per-circuit statistics
• More balanced flow of traffic across links

49
Overlay Networks

• ATM core ringed by routers
• PVCs overlaid onto physical network

A
Physical View
B
C
A
Logical View
C
B
50
vBNS ATM Design

• Full UBR PVP mesh between terminal switches to
  carry Best Effort traffic

51
vBNS Backbone Network Map
Seattle
C
Boston
Cleveland
Ameritech NAP
C
National Center for Atmospheric Research
Chicago
New York City
C
A
C
A
C
C
Sprint NAP
C
C
Perryman, MD
C
Pittsburgh Supercomputing Center
A
San Francisco
C
Denver
C
C
C
National Center for Supercomputing Applications
C
J
Washington, DC
MFS NAP
Los Angeles
J
C
C
A
Atlanta
San Diego Supercomputer Center
C
Ascend GRF 400 Cisco 7507 Juniper M40 FORE
ASX-1000 NAP
DS-3 OC-3C OC-12C OC-48
A
C
Houston
C
J
52
Overlay Nets Had Drawbacks

• Growth in full mesh of ATM PVCs stresses
  everything
• Router IGP runs out of steam
• Practical limitation of updating configurations
  in each switch and router
• ATM 20 Cell Tax
• ATM SAR speed limitations
• OC-48 SAR very difficult/expensive to build
• OC-192 SAR?

53
In the mean time

• Routers caught up
• Current generation of routers have
• High speed, wire-rate interfaces
• Deterministic performance
• Software advances
• MPLS came along
• Fuses best aspects of ATM PVCs with
  high-performance routing engines
• Uses low-overhead circuit mechanism
• Automates path selection and configuration
• Implements quick failure recovery

54
MPLS for Traffic Engineering

• Low-overhead virtual circuits for IP
• Originally designed to make routers faster
• Fixed label lookup faster than longest match used
  by IP routing
• Not true anymore
• Value of MPLS is now in traffic engineering
• Other MPLS Benefits
• No second network
• A fully integrated IP solution no second
  technology
• Traffic engineering
• Lower cost
• A CoS enabler
• Failover/link protection
• Multi-service and VPN support

55
AGENDA

• MPLS Overview
• Traffic Engineering
• VPNs

56
What Is a Virtual Private Network?
Corporate headquarters
Intranet
Branch office
Shared Infrastructure
Mobile users and telecommuters
Remote access
Suppliers, partners and customers
Extranet

• A private network constructed over a shared
  infrastructure
• Virtual
• An artificial object simulated by computers (not
  really there!)
• Private
• Separate/distinct environments
• Separate addressing and routing systems
• Network
• A collection of devices that communicate among
  themselves

57
Deploying VPNs using Overlay Networks
Provider Frame Relay Network
DLCI
DLCI
DLCI

• Operational model
• PVCs overlay the shared infrastructure (ATM/Frame
  Relay)
• Routing occurs at CPE
• Benefits
• Mature technologies
• Inherently secure
• Service commitments (bandwidth, availability,
  etc.)
• Limitations
• Scalability and management of the overlay model
• Not a fully integrated IP solution

58
MPLS A VPN Enabling Technology

• Benefits
• Seamlessly integrates multiple networks
• Permits a single connection to the service
  provider
• Supports rapid delivery of new services
• Minimizes operational expenses
• Provides higher network reliability and
  availability

59
There are Three Types of VPNs

• End to End (CPE Based) VPNs
• L2PT PPTP
• IPSEC
• Layer 2 VPNs
• CCC
• CCC MPLS Hybrid
• Layer3 VPNs
• RFC 2547bis

60
End to End VPNsL2TP and PPTP
V.x modem
L2TP tunnel
Dial Access Provider
Service Provider or VPN
PPP dial-up
PPTP tunnel

• Application Dial access for remote users
• Layer 2 Tunneling Protocol (L2TP)
• RFC 2661
• Combination of L2F and PPTP
• Point-to-Point Tunneling Protocol (PPTP)
• Bundled with Windows/Windows NT
• Both support IPSec for encryption
• Authentication encryptionat tunnel endpoints

61
End to End VPNs The IP Security Protocol (IPSec)

• Defines the IETFs layer 3 security architecture
• Applications
• Strong security requirements
• Extend a VPN across multiple service providers
• Security services include
• Access control
• Data origin authentication
• Replay protection
• Data integrity
• Data privacy (encryption)
• Key management

62
End to End VPNs IPSec Example
Public Internet
CPE
CPE
IPSec ESP Tunnel Mode

• Routing must be performed at CPE
• Tunnels terminate on subscriber premise
• Only CPE equipment needs to support IPSec
• Modifications to shared resources are not
  required
• ESP tunnel mode
• Authentication insures integrity from CPE to CPE
• Encrypts original header/payload across internet
• Supports private address space

63
Layer 2 VPNs CCC/MPLS
LSPs
PE
PE
DLCI 600
DLCI 506
CPE
CPE
LSP 5
PE
ATM (or Frame Relay)
ATM (or Frame Relay)
LSP 2
LSP 6
DLCI 610
DLCI 408
(MPLS core)

• Benefits
• Reduces provider configuration complexity
• MPLS traffic engineered core
• Subscriber can run any Layer 3 protocol
• User Nets do not know there is a cloud in the
  middle
• Limitations
• Circuit type (ATM/FR) must be like to like

64
CCC Example Abilene and ISP Service on one link
Big I Internet Traffic ATM VC1 terminated, IP
packets delivered to Qwest ISP
Qwest ISP
Abilene
M40
University X
Abilene Traffic ATM VC2 mapped to port facing
Abilene
ATM Access
An M20/40/160 can both terminate ATM PVCs (layer
3 lookup) and support CCC pass-through on the
same port.
65
vBNS used CCC and MPLS to tunnel IPv6 across
their backbone for SC2000
vBNS/vBNS IPv4
CCC
CCC
Chicago
LSP
SC2000 in Dallas
ATM
ATM
IPv6
66
Layer 3 VPNsRFC 2547 - MPLS/BGP VPNs

• MPLS (Multiprotocol Label Switching) is used for
  forwarding packets over the backbone
• BGP (Border Gateway Protocol) is used for
  distributing routes over the backbone
• Multiple Forwarding Tables (FT) on some edge
  routers, one for each VPN

67
Questions?
68
Thank You

• jjamison_at_juniper.net
• http//www.juniper.net