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© 2009 Cisco Systems, Inc. All rights reserved. Cisco PublicIntro to MPLSLuc De Ghein 1
Introduction to MPLS
Luc De [email protected]
Cisco Public 2© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Agenda
History of MPLS
Benefits of MPLS
MPLS Technology Introduction
MPLS Applications
Cisco Public 3© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Before MPLS
Several WAN protocols existed
•ATM, Frame-Relay
• They were cost-effective
• Lacked ease of deployment, provisioning, and management
• IP was winning the battle
• Ethernet was cheaper and easier than ATM
• People began to look for
•a good integration of IP over ATM
•an easy way to deploy virtual private networks over an IP backbone
Cisco Public 4© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
History of MPLS
1998 1999 2000 2001
Time
2002 2003 2004 2009+2005 2006 2007 2008
Cisco Public 5© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Benefits of MPLS
One unified network infrastructure
Better IP over ATM integration
BGP-free core
Peer-to-peer Virtual Private Network (VPN) model
Optimal traffic flow across provider network
Flexible way to do traffic engineering
economics
Cisco Public 6© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
One Unified Network Infrastructure MPLS = Multi Protocol Label Switching
An MPLS backbone is an enabler for multiservice
Carry all kinds of traffic across one MPLS enabled network :
–IPv4
–IPv6
–Layer 2 frames (Ethernet, ATM, Frame-Relay, HDLC, PPP)
–TDM
Adding labels to the packet enables the possibility to carry other protocols than just IP over an MPLS-enabled Layer 3 IP backbone, similarly to what was previously only possible with Frame Relay or ATM Layer 2 networks
Ethernet
ATM
IP VPN
Frame RelayPPP
IP/MPLS
Internet
VoIP
IPv6
PSTN
Cisco Public 7© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Better IP over ATM Integration
Before MPLS, there were three ways to implement MPLS:
–(RFC) 1483, “Multiprotocol Encapsulation over ATM Adaptation Layer 5,”•all ATM circuits had to be manually established and all mappings between IP next hops and ATM endpoints had to be manually configured on every ATM-attached router in the network
–LANE (LAN Emulation)•this technology never achieved the scalability or reliability requirements of large service provider networks
–MPOA (Multiprotocol over ATM )•the tightest integration of IP over ATM, but also the most complex solution
All these methods were cumbersome to implement and troubleshoot. A better solution for integrating IP over ATM was one of the driving reasons for the invention of MPLS.
The prerequisites for MPLS on ATM switches were that the ATM switches had to become more intelligent. The ATM switches had to run an IP routing protocol and implement a label distribution protocol.
Cisco Public 8© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
BGP sessions
edge MPLS router
edge MPLS router
edge MPLS router
BGP Route Reflector
(RR)
edge MPLS router
MPLS network
BGP-free core
BGP-Free Core
•MPLS labeling is done on edge routers – the label assigned is the one associated with the BGP next-hop address
•The BGP next-hop address is known in the network via the IGP
•Forwarding on core routers is done by looking at MPLS label – there is no IP lookup
•Core routers do not need to run BGP
Cisco Public 9© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
The Peer-to-Peer Model for MPLS VPN
A Virtual Private Network (VPN) is a network that emulates a private network over a common infrastructure.
In the overlay model:
–Examples are ATM and Frame-Relay
–The service provider provides a service of point-to-point links or virtual circuits across his network between the routers of the customer
–The customer routers form routing peering between them directly across the links or virtual circuits from the service provider
In the peer-to-peer VPN model:
–The service provider’s routers carry the customer’s data across the network, but they also participate in the customers’ routing
–Easier provisioning
•Adding one customer site means that on the PE router only the peering with the CE router must be added
•There is no hassle with creating many virtual circuits as with the overlay model or with configuring packet filters or route filters with the peer-to-peer VPN model over an IP network
Cisco Public 10© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
service providers’ Frame Relay or ATM network
The Overlay Model for VPN
In the overlay model:
–The service provider provides a service of point-to-point links or virtual circuits across his network between the routers of the customer
–The customer routers form routing peering between them directly across the links or virtual circuits from the service provider
VPN green customer routerVPN red
customer router
virtual circuit
Frame Relay or ATM switch
VPN red customer router
VPN red customer router
VPN green customer router
VPN green customer router
Cisco Public 11© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Peer-to-Peer Model for MPLS VPN
routing peering
routing peeringrouting peering
Provider Edge router
Provider Edge router
Provider Edge router
Customer Edge router
Customer Edge router
Customer Edge router
routing peering = iBGP
In the peer-to-peer model:
–One peering: between the CE router and the PE router
–Internal BGP takes care of the VPN routing in SP network
Cisco Public 12© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Optimal Traffic Flow
Frame Relay or ATM switch
VPN red CE
VPN red CE
VPN red CE
VPN red CE
VPN red CE
VPN red CE
overlay model peer-to-peer model
Layer 2 devices in the core: customer routers interconnect through them by means of virtual circuits (VC) created
In order for any router to send traffic directly to any other router at the edge, a virtual circuit must be created between them directly
–For optimal traffic flow in all cases: full mesh needed
–For n customer routers: (n-1) * n / 2 number of VCs needed
Peer-to-peer MPLS VPN model has optimal traffic flow in all cases
No VCs per customer
Frame Relay or ATM switch
VPN red CE
VPN red CE
VPN red CE
VPN red CE
VPN red CE
VPN red CE
Cisco Public 13© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Traffic Engineering – MPLS TE
If this network is an IP only network, you could never have router B send the traffic along the bottom path by configuring anything on router A. Router B’s decision to send traffic on the top or bottom path is solely its own decision.
If you enable MPLS traffic engineering in this network, you can have router A send the traffic towards router D along the bottom path. The MPLS TE forces router B to toward the traffic A-D onto the bottom path. This can be done in MPLS because of the label forwarding mechanism.
A B D
C
E F
traffic engineered path
least cost pathMPLS network with TE enabled
MPLS TE = optimally use the network
TE looks how much BW is free on any link
Use underutilized links
TE must provide the possibility to steer traffic through the network on paths different than the preferred path (least cost path)
IP IP
© 2009 Cisco Systems, Inc. All rights reserved. Cisco PublicIntro to MPLSLuc De Ghein 14
MPLS Technology Introduction
Cisco Public 15© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
MPLS Label and Label Encapsulation
LabelPPP Header Layer 2/L3 PacketPPP Header(Packet over SONET/SDH)
Label MAC Header Layer 2/L3 PacketLAN MAC Label Header
MPLS Label Encapsulation
COS/EXP = Class of Service: 3 Bits; S = Bottom of Stack; TTL = Time to Live
0 1 2 30 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
Label # – 20bits EXP S TTL-8bits
MPLS Label
Cisco Public 16© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Label Stacking
There may be more than one label in an MPLS packet
Each label at a different place in the label stack has its meaning•Example—there can be one label for routing the packet to an egress point and another that separates a customer A packet from customer B
•Inner labels can be used to designate services
•e.g. L3VPNs, L2VPN
Outer label used to route/switch the MPLS packets in the network
Last label in the stack is marked with EOS bit
Allows building services such as MPLS VPNs
Traffic engineering and fast reroute
VPNs over traffic engineered core
Any transport over MPLS
TE Label
LDP Label
VPN Label
Inner Label
Outer Label
IP Header
Cisco Public 17© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
MPLS Label
MPLS Label has local significance
One router assigns the MPLS label independently
There is no global assignment for the whole network
–No global authority
20 bits for the label gives label range of 0-1048575
–Default label range might be lower
–Label range is limited on some platforms
Normal MPLS labels are: 16-1048575
Reserved label range is: 0-15
–See later slides for some examples
Cisco Public 18© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
LDP Label Advertisment
P PPE PE
10.0.0.0/8 label L3
LDP label advertisement
10.0.0.0/8 label L2
LDP label advertisement
10.0.0.0/8 label L1
LDP label advertisement
10.0.0.0/8
Local/In label
Prefix Out Intf Remote/Out Label
L1 10.0.0.0/8 POS0/0/0 L2
LFIB
LDP = Label Distribution Protocol, defined in RFC 3035 and 3036
LDP advertises label bindings
Label binding = IP prefix + MPLS label
LDP is a superset of Tag Distribution Protocol
IGP LDP
Cisco Public 19© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Label Packet Forwarding
IGP LDP
IP Label L1IP Label L2IP Label L3IP IP
P PPE PE
Local/In label
Prefix Out Intf Remote/Out Label
L1 10.0.0.0/8 POS0/0/0 L2
swapping incoming label with outgoing label
Cisco Public 20© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Control and Forward Plane Separation
LFIB
Routing
Process
MPLS Process
RIB
LIB
FIB
control plane
Label BindingUpdates/
Adjacency
IP TrafficMPLS Traffic
control plane used to distribute labels and build label-switched paths (LSPs)
Route Updates/
Adjacency
forwarding plane
forwarding plane used to forward IP or labeled packets
Cisco Public 21© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
LIB Label Information Base holds the label bindings
–One local label (in label) allocated by the router per prefix
–One or more remote labels (out label) per prefix LIB stores all received label bindings
PE1#show mpls ldp binding
tib entry: 10.1.1.0/24, rev 3
local binding: tag: imp-null
remote binding: tsr: 10.100.1.3:0, tag: imp-null
remote binding: tsr: 10.100.1.6:0, tag: 16
tib entry: 10.1.5.0/24, rev 20
local binding: tag: imp-null
remote binding: tsr: 10.100.1.3:0, tag: 18
remote binding: tsr: 10.100.1.6:0, tag: imp-null
tib entry: 10.100.1.2/32, rev 4
local binding: tag: imp-null
remote binding: tsr: 10.100.1.3:0, tag: 16
remote binding: tsr: 10.100.1.6:0, tag: 19
tib entry: 10.100.1.4/32, rev 18
local binding: tag: 22
remote binding: tsr: 10.100.1.3:0, tag: 19
remote binding: tsr: 10.100.1.6:0, tag: 21
...
one LIB entry
Cisco Public 22© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
LFIB
Label Forwarding Information Base LFIB stores one local and one remote label per prefix LFIB is used to forward labeled incoming packet
–Outgoing packet can be labeled
–Outgoing packet can be unlabeled
PE1#show mpls forwarding-table
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
16 Pop tag 10.1.2.0/24 0 Et0/0 10.1.5.6
17 Pop tag 10.1.3.0/24 0 Se3/0 point2point
18 Pop tag 10.1.4.0/24 0 Se3/0 point2point
19 Pop tag 10.100.1.3/32 0 Se3/0 point2point
20 Pop tag 10.100.1.6/32 0 Et0/0 10.1.5.6
21 Aggregate 11.1.1.0/24[V] 0
22 19 10.100.1.4/32 0 Se3/0 point2point
23 Untagged 11.100.1.1/32[V] 0 Se2/0 point2point
Cisco Public 23© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Label Forwarding Operations
16
IPIP
34
SWAP
16
IPIP
34
55
PUSH
IPIP
16
POP
16
23
IPIP
UNTAG/ NO LABEL
16
23
Cisco Public 24© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Implicit Null Label -> PHP
P PPE PE
Label L1IP Label L2IPIP IP
penultimate hop router
Implicit null label (label 3) is used in a few cases–for example for connected routes
Purpose: avoid double lookup: first MPLS lookup, followed by IP lookup
Penultimate Hop Popping (PHP)
removing the MPLS label at the one-but-last MPLS router
P#show mpls forwarding-table 10.100.1.0 255.255.255.0Local Outgoing Prefix Bytes tag Outgoing Next Hop tag tag or VC or Tunnel Id switched interface 17 Pop tag 10.100.1.0/24 5948 Se3/0 point2point
P#show mpls ldp bindings 10.100.1.0 24 tib entry: 10.100.1.0/24, rev 14 local binding: tag: 17 remote binding: tsr: 10.100.1.6:0, tag: 19 remote binding: tsr: 10.100.1.1:0, tag: imp-null remote binding: tsr: 10.100.1.4:0, tag: 19
10.0.0.0/8 label 3
LDP label advertisement
10.100.1.0/24
POP is outgoing label in LFIB
(no label is added in the label stack)
Cisco Public 25© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Explicit Null Label Label 0 is advertised
Label 0 is put in the label stack
Double lookup needed
Label 0 does not entail a forwarding vector, but QOS information (EXP bits) is used of explicit null label
–The QOS information is retained till the last hop, whereas with PHP, the QOS information in the top label is lost, because the top label was popped
P PPE PE
Label L1IP Label L2IPIP
penultimate hop router
replacing label with explicit-null label
10.0.0.0/8 label 0
LDP label advertisement
10.100.1.0/24Label 0IP
!
mpls label protocol ldp
mpls ldp explicit-null
!
P#show mpls ldp bindings 10.100.1.0 24
tib entry: 10.100.1.0/24, rev 14
local binding: tag: 17
remote binding: tsr: 10.100.1.6:0, tag: 19
remote binding: tsr: 10.100.1.4:0, tag: 19
remote binding: tsr: 10.100.1.1:0, tag: exp-null
P#show mpls forwarding-table 10.100.1.0
Local Outgoing Prefix Bytes tag Outgoing Next Hop
tag tag or VC or Tunnel Id switched interface
17 0 10.100.1.0/24 0 Se3/0 point2point
Cisco Public 26© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Overview of MPLS Applications
MPLS Layer 3 VPNs
MPLS Layer 2 VPNs
•Point-to-point
•Point-to-multipoint
MPLS Traffic Engineering
Cisco Public 27© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
MPLS VPN – Control Plane
P PPE PE
red VPN
red VPN
eBGPIGP
eBGPIGP
iBGP exchanging vpnv4 prefixes + MPLS label
VRF interface
VRF interface
Route Distinguisher (RD): 8-byte field—unique value assigned by a provider to each VPN to make different VPN routes unique
VPNv4 address: RD+VPN IP prefix Route Target (RT): 8-byte field, unique value assigned by a provider to define the import/export rules for the routes from/to
each VPN MP-iBGP: facilitates advertisement of VPNv4* prefixes + labels between BGP peers Virtual Routing Forwarding Instance (VRF): contains VPN site routes; only on PE routers Multi-VRF CE (VRF-Lite): CE device supporting multiple VRFs w/o MP-iBGP & VPN labels
IGPLDP
IGPLDP
IGPLDP
CECE
Cisco Public 28© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
MPLS VPN – Data Forwarding
IGP LDP
P PPE PE
VPN Label IP Label L2 VPN Label IP Label L1 VPN Label IP IP
Penultimate Hop Popping (PHP)
Ingress PE router: lookup in VRF RIB, adds vpn label, add LDP label P routers: label swapping (top label only) Egress PE router: looks up vpn label in LFIB, forwards IP packet onto VRF interface
IP
red VPN
red VPN
CECE
Cisco Public 29© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
VPLSVirtual Private LAN Service
Point to Multipoint
VPLSVirtual Private LAN Service
Point to Multipoint
VPWSVirtual Private Wire Service
Point to Point
VPWSVirtual Private Wire Service
Point to Point
L2VPN ModelsL2VPN Models
L2VPN Options
AToMAToML2TPv3L2TPv3
IP CoreIP Core
Frame RelayFrame Relay
ATM (AAL5 and Cell)ATM (AAL5 and Cell)
EthernetEthernet
PPP and HDLCPPP and HDLC
MPLS CoreMPLS Core
Frame RelayFrame Relay
ATM (AAL5 and Cell)ATM (AAL5 and Cell)
EthernetEthernet
PPP and HDLCPPP and HDLC
MPLS CoreMPLS Core
EthernetEthernet
AToM = Any Transport over MPLS
Cisco Public 30© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Any Transport over MPLS ArchitectureIETF’s Pseudo-Wire Reference Model
PE PE
PSN Tunnel
pseudo wires
AC
AC
AC
AC
emulated services
IETF working group PWE3 ‘Pseudo wire emulation edge to edge’ requirements detailed in
draft-ietf-pwe3-requirements now RFC3916
draft-ietf-pwe3-architecture(framework) now RFC3985
• The pseudowire (PW) is a connection between 2 PE routers emulating an end-to-end service and connecting 2 Attachments Circuits (AC)
Cisco Public 31© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
IETF’s L2VPN Logical Context
An L2VPN is comprised of switched connections between subscriber endpoints over a shared network
Non-subscribers do not have access to those same endpoints
Ethernet
ATM
HDLCPPP
FR
Pseudo Wire
SP Network
SP InterconnectionProviderEdge
Many Subscriber Encapsulations Supportable
ProviderEdge
Cisco Public 32© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
AToM Building Blocks
Emulated VC encapsulation (control word) Information on enclosed Layer 2 PDU
4 bytes sitting in between the label stack and the MPLS payload
Control
Connection
Transport
Component
Tunneling
Component
Emulated L2
PDU
Targeted LDP (Label Distribution Protocol) SessionUsed for VC-label negotiation, withdrawal, error notification
Tunnel header (tunnel label)To get PDU from ingress to egress PE using MPLS LSP
Demultiplexer field (VC label)To identify individual circuits within a tunnel (VC label is a MPLS Label)
Cisco Public 33© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Any Transport over MPLS ControlPlane — How PWs Are Established
PE1 PE2
3. PE1 Allocates VC Label for new interface and binds to configured VC ID
4. PE1 sends label mapping message to PE2 over LDP session
5. PE2 Receives VC Type and VC Label that matches Local VCID
1. CE-PE: AC connection
PP
Note: PE2 Repeats Steps1–5 so that BidirectionalLabel/VCID MappingsAre Established
CECE
2. PE1 Starts Targeted LDP session with PE2 if one does not already exist
Cisco Public 34© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Any Transport over MPLS — How Traffic Is Forwarded on an Emulated Circuit
PE1 PE2PP CECE
VC Label L2 frame Label L1 VC Label L2 frameL2 frame L2 frame
VC label
LDP label
VC Label L2 frame Label L2
VC label is only looked up at egress PE Tunnel label (LDP/IGP label) is changed at every hop
Cisco Public 35© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Virtual Private LAN Service Overview
PE1 PE2
MPLS WAN
Site3CE
Site2CE
Site1CE
VPLS defines an architecture that delivers Ethernet Multipoint Services (EMS) over an MPLS network
VPLS operation emulates an IEEE Ethernet bridge. VPLS network acts like a virtual switch that emulates conventional L2 bridge.
•Forwarding of ethernet frames
•Forwarding of unicast frames with unknown destination MAC address
•Forwarding of multicast and broadcast frames
•Dynamic learning of MAC addresses
•MAC address aging
It supports communication between fully meshed L2 sites without the spanning tree complexities
Cisco Public 36© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Full mesh of PWs between VSIs
VPLS Components
Virtual Switching Instance: VSI or VFI (Virtual Forwarding Instance)
VPN ID: Unique value for each VPLS VPN
Attachment VCs are port mode or VLAN ID
Directed LDP session between participating PEs
n-PE n-PE
PW
PW
PW
CE
CE
CE
CE
CE
CE
CE
Tunnel LSP
Green VSIBlue VSIRed VSI
Green VSIBlue VSIRed VSI
Attachment Circuit
full mesh of Targeted-LDP sessions exchange VC labels
Tunnel LSP Tu
nnel
LS
P
Cisco Public 37© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
R2
R1
R8
IP/MPLS
R2
R1
R8
IP/MPLS
R2
R1
R8
IP/MPLS
R2
R1
R8
IP/MPLS
MPLS TE Deployment Models
Bandwidth OptimizationStrategic Tactical
Protection Point-to-Point SLA
move BW away from congested pointsdeploy TE everywhere; optimise BW everywhere
Virtual Leased Lines; QOS; BW guaranteesFast ReRouting (FRR)
Cisco Public 38© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
How MPLS TE Works
Link information Distribution
– ISIS-TE
– OSPF-TE
Path Calculation (CSPF)
Path Setup (RSVP-TE)
Forwarding Traffic down Tunnel
– Auto-route
– Static
– PBR
– CBTS
– Forwarding Adjacency
– Tunnel select
IP/MPLS
Head end
Mid-point Tail end
Cisco Public 39© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
TE Fundamentals
1. Information Distributionneed Link State protocol IS-IS or OSPF
2. Path selection/calculation
3. Path setup
4. Trunk admission control
5. Forwarding trafficon to tunnel
6. Path maintenance
RSVP/TE used to distribute labels, provide CAC, failure notification, etc.
Unidirectional Tunnel Upstream Downstream
headendtailend
midpoints
Path Calculation (PCALC/CSPF) — uses IGP advertisements to compute “constrained” paths
IGP (OSPF or ISIS) used to flood BW information
TE tunnel
Cisco Public 40© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Path Setup Example
headendtailend
TE tunnel
PATH
RESVRESV
RESV
PATH
PATH
PCALC calculates path on headend or explicit path configured
PATH messages are sent with requested bandwidth
RESV messages are sent with MPLS label for the TE tunnel
There is admission control at each hop to see if the bandwidth requirement can be met
Headend router has view of complete network topology
in TE database
thanks to link state topology on headend router
Cisco Public 41© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
MPLS TE Fast Re-Route (FRR)
Subsecond recovery against node/link failures
Fast because backup tunnel is pre-signaled
Scalable 1:N protection
Greater protection granularity
Cost-effective alternative to optical protection
Bandwidth protection
Primary TE LSP
Backup TE LSP
IP/MPLS
R2
R1
R8
Cisco Public 42© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Requires next-hop (NHOP) backup tunnel
Point of Local Repair (PLR) swaps label and pushes backup label
Backup terminates on Merge Point (MP) where traffic rejoins primary
Restoration time expected under ~50 ms
FRR Link Protection Operation
Primary TE LSP
Backup TE LSP
IP/MPLS
R1
2525
2222
1616 2222
2222
R2 R6 R7
R3
R5
Cisco Public 43© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
FRR Node Protection Operation
Primary TE LSP
Backup TE LSP
IP/MPLS
R1
2525
3636
1616 2222
3636
R2 R5 R6
R3
R4
Requires next-next-hop (NNHOP) backup tunnel
Point of Local Repair (PLR) swaps next-hop label and pushes backup label
Backup terminates on Merge Point (MP) where traffic rejoins primary
Restoration time depends on failure detection time
3636
R5
Cisco Public 44© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Path Protection Operation
Primary TE LSP
Backup TE LSP
IP/MPLS
R1 R2 R3 R4
R6R5 R7
No local repair
Requires second end-to-end signalled TE LSP
Point of Repair (PLR) is headend router
Restoration time expected under ~200 ms
© 2009 Cisco Systems, Inc. All rights reserved. Cisco PublicIntro to MPLSLuc De Ghein 45
Q&A
Cisco Public 46© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Terminology ReferenceTerminology Description
AC Attachment Circuit. An AC Is a Point-to-Point, Layer 2 Circuit Between a CE and a PE.
ECMP Equal Cost Multipath
IGP Interior Gateway Protocol
LAN Local Area Network
LDP Label Distribution Protocol, RFC 3036.
LER Label Edge Router. An Edge LSR Interconnects MPLS and non-MPLS Domains.
LFIB Labeled Forwarding Information Base
LIB Labeled Information Base
LSP Label Switched Path
LSR Label Switching Router
P Router An Interior LSR in the Service Provider's Autonomous System
PE RouterAn LER in the Service Provider Administrative Domain that Interconnects the Customer Network and the Backbone Network.
PSN Tunnel Packet Switching Tunnel
Cisco Public 47© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein
Terminology ReferenceTerminology Description
Pseudo-WireA Pseudo-Wire Is a Bidirectional “Tunnel" Between Two Features on a Switching Path.
PWE3 Pseudo-Wire End-to-End Emulation
RD Route Distinguisher
RIB Routing Information Base (Routing Table)
RR Route Reflector
RT Route Target
RSVP-TE Resource Reservation Protocol based Traffic Engineering
VPN Virtual Private Network
VFI Virtual Forwarding Instance
VPLS Virtual Private LAN Service
VPWS Virtual Private WAN Service
VRF Virtual Route Forwarding Instance
VSI Virtual Switching Instance
Cisco Public 48© 2009 Cisco Systems, Inc. All rights reserved.Intro to MPLSLuc De Ghein