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MPLS Introduction Training
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confidentialGBS-MKT-Global-10_001
Monaco, 2011-09-08
MPLS Introduction
Executive Training Session
Delivered to CW (M&I)
GBS-MKT-Global-10_001Global Business Solutions SAL
• Introduction
• Application
• Features
• Implementation
• Audit Service
Agenda
GBS-MKT-Global-10_001Global Business Solutions SAL
• Basic Concept
• Architecture
• Operation Modes
• LSR Architecture
• Forwarding
• Label & Stack
Introduction
GBS-MKT-Global-10_001Global Business Solutions SAL
• MPLS?
� Multi-Protocol Label Switching
� New forwarding mechanism based on labels• Destination IP networks (traditional routing)
• Source network, QoS, bandwidth, etc…
� Support other forwarding mechanism
Basic Concept
GBS-MKT-Global-10_001Global Business Solutions SAL
• Edge routers:� Lookup routes
� Assign labels
• Core routers:� Switch packets
� Swap labels
• All forwarding based
MPLS Example
GBS-MKT-Global-10_001Global Business Solutions SAL
10.1.1.110.1.1.1
Routing lookup and
label assignment10.0.0.0/8 ���� L=5
Label swappingL=5 ���� L=3
Label removal and
routing lookupL=3
MPLS Example (image)
GBS-MKT-Global-10_001Global Business Solutions SAL
• MPLS architecture is divided between 2 main components:
• Control plane:� Exchange L3 routing info and labels
• Routing: OSPF, EIGRP, BGP, IS-IS, etc…
• Labels: TDP, LDP, BGP, RSVP, etc…
� Maintain the label switching database• LFIB: label forwarding information base
• Data plane:� Simple forwarding engine
MPLS Architecture
GBS-MKT-Global-10_001Global Business Solutions SAL
Data plane
Control plane
OSPF: 10.0.0.0/8
LDP: 10.0.0.0/8
Label 17
OSPF
LDP
LFIB
LDP: 10.0.0.0/8
Label 4
OSPF: 10.0.0.0/8
4����17
Labeled packet
Label 4
Labeled packet
Label 17
MPLS Architecture (image)
GBS-MKT-Global-10_001Global Business Solutions SAL
• MPLS can be used everywhere regardless of L1/2 (media/protocol)
• MPLS have 2 modes of operations:� Frame mode: insert a 32b label field between L2 and L3
� Cell mode: use other layer header (MPLS over ATM)
• MPLS domain is the group of core and edge routers (LSR) that work together.
MPLS Operation Modes
GBS-MKT-Global-10_001Global Business Solutions SAL
MPLS DomainMPLS DomainMPLS DomainMPLS Domain
Edge Edge Edge Edge
LSRLSRLSRLSR
LSRLSRLSRLSR
10.1.1.110.1.1.110.1.1.110.1.1.1 L=L=L=L=3333 L=L=L=L=5555
L=L=L=L=43434343L=L=L=L=3131313120.1.1.120.1.1.120.1.1.120.1.1.1
10.1.1.110.1.1.110.1.1.110.1.1.1
20.1.1.120.1.1.120.1.1.120.1.1.1
MPLS Domain (image)
GBS-MKT-Global-10_001Global Business Solutions SAL
• LSR (Label Switch Router) types:� Core LSR: forward labeled packet (swap labels)
� Edge LSR: labels packets and send them to domain
• LSR functions:� Exchange routing info
� Exchange labels
� Forward packets or cell (data plane)
LSR Architecture
GBS-MKT-Global-10_001Global Business Solutions SAL
LSR
Control plane
Data plane
Routing protocol
Label distribution protocol
Label forwarding table
IP routing table
Exchange ofrouting information
Exchange oflabels
Incoming
labeled packets
Outgoing
labeled packets
LSR Architecture (image)
GBS-MKT-Global-10_001Global Business Solutions SAL
• FEC (Forwarding Equivalent Class):
� IP Packet classification
� Group having same forwarding manner• Over the same path
• Having the same treatment
FEC
GBS-MKT-Global-10_001Global Business Solutions SAL
• MPLS forwarding:� Assign a packet to a FEC (label)
� Determine the next-hop (routing)
• LSR perform the following functions:� Insert (impose) a label or a stack of labels on ingress.
� Swap a label with a next-hop label or a stack of labels in the core.
� Remove (pop) a label on egress.
MPLS Forwarding
GBS-MKT-Global-10_001Global Business Solutions SAL
MPLS Forwarding (image)
MPLS Domain
10.1.1.1
IP Lookup
10.0.0.0/8 ����
label 3
LFIB
10.1.1.1/8 ����label 3
IP Lookup
10.0.0.0/8 ����
label 5
LFIBlabel 3 ����label 5
IP Lookup
10.0.0.0/8 ����
next hop
LFIBlabel 5 ���� pop
10.1.1.13 10.1.1.15 10.1.1.1
GBS-MKT-Global-10_001Global Business Solutions SAL
• Label – 32b field between L2 & L3:� 20b: label (number)
� 3b: experimental (carry precedence value)
� 1b: bottom-of-stack (indicator if last label)
� 8b: TTL (prevent indefinite looping)
• Label Stack Scenarios:� MPLS/VPN (next router / VPN tunnel)
� Traffic Engineering (endpoint tunnel / destination)
� Combined MPLS/VPN & Traffic Engineering
Label & Stack
GBS-MKT-Global-10_001Global Business Solutions SAL
• Unicast IP routing
• Multicast IP routing
• Traffic Engineering
• QoS
• VPN
Applications differ only in the control plane
Applications
GBS-MKT-Global-10_001Global Business Solutions SAL
• IP routing protocol (OSPF, EIGRP, …)� Carry info about network reachability
• Label distribution protocol (LDP or TDP)� Bind labels to networks learned
• FEC = destination network� Stored in the routing table
Unicast IP routing
GBS-MKT-Global-10_001Global Business Solutions SAL
• No dedicated protocol is needed� Natively built into MPLS
� PIMv2 propagate routes and labels
• FEC = destination multicast address� Stored in the multicast table
Multicast IP routing
GBS-MKT-Global-10_001Global Business Solutions SAL
• IP routing protocol (OSPF or IS-IS)� Holds the entire routing topology
� IGP is an extension to MPLS/TE
• Establish tunnel (RSVP or CR-LDP)� Propagate labels
• IGP: internal gateway protocol
• RSVP: resource reservation protocol
• CR-LDP: constraint-based routed LDP
Traffic Engineering
GBS-MKT-Global-10_001Global Business Solutions SAL
• Extension to unicast� Differentiated services
� LDP/TDP extension
• FEC = destination network + service class
QoS
GBS-MKT-Global-10_001Global Business Solutions SAL
• Networks are learned via:� IGP from a customer
� BGP from internal routers
• Label propagate via multi-protocol BGP� 1st: points to the egress router (LDP or TDP)
� 2nd: points to a routing table or egress interface
• FEC=VPN site descriptor or routing table
VPN
GBS-MKT-Global-10_001Global Business Solutions SAL
Control plane
MulticastIP Routing
MPLS Traffic Engineering
QoS MPLS/VPNUnicast IP Routing
Data plane
Any IGP
LDP/TDP
Label forwarding table
Unicast IProuting table
PIM version 2
MulticastIP routing table
OSPF or IS-IS
LDP
Unicast IProuting table
RSVP
Any IGP
LDP/TDP
Unicast IProuting table
Any IGP
LDP
Unicast IProuting tables
BGP
Applications (image)
GBS-MKT-Global-10_001Global Business Solutions SAL
• AToM: Any Transport over MPLS� L2 frames: Ethernet, FR, ATM, PPP, HDLC
� Transport L2 traffic over IP/MPLS backbone
� Single, integrated, packet based infrastructure
� Higher availability, performance, scalability
• Examples:� Ethernet over MPLS, application: TLS and VPLS
� Frame-Relay over MPLS, carry: BECN, FECN, BE
� ATM over MPLS
AToM
GBS-MKT-Global-10_001Global Business Solutions SAL
• Neighbors Discovery
• Label Distribution
• Packet Propagation
• Convergence
Features
GBS-MKT-Global-10_001Global Business Solutions SAL
• LDP & TDP have similar process:� Send “Hello” message on the interface (UDP)
� Respond by establishing a session (TCP)
� LDP port number is 646
� UDP multicast address 224.0.0.2
• LSR establish one LDP session per label space� Combination of frame mode, cell mode or multi cell
mode results in multiple LDP sessions
Neighbours Discovery
GBS-MKT-Global-10_001Global Business Solutions SAL
1.0.0.1 1.0.0.3
1.0.0.4
MPLS_D
1.0.0.2
UDP: Hello
(1.0.0.1:1050 � 224.0.0.2:646)
UDP: Hello
(1.0.0.1:1050 � 224.0.0.2:646)
UDP: Hello
(1.0.0.4:1033 � 224.0.0.2:646)
UDP: Hello
(1.0.0.4:1033 � 224.0.0.2:646)
UDP: Hello
(1.0.0.2:1064 � 224.0.0.2:646)
UDP: Hello
(1.0.0.2:1064 � 224.0.0.2:646)
UDP: Hello
(1.0.0.1:1051 � 224.0.0.2:646)
UDP: Hello
(1.0.0.1:1051 � 224.0.0.2:646)
UDP: Hello
(1.0.0.4:1034 � 224.0.0.2:646)
UDP: Hello
(1.0.0.4:1034 � 224.0.0.2:646)
UDP: Hello
(1.0.0.2:1065 � 224.0.0.2:646)
UDP: Hello
(1.0.0.2:1065 � 224.0.0.2:646)
UDP: Hello
(1.0.0.1:1052 � 224.0.0.2:646)
UDP: Hello
(1.0.0.1:1052 � 224.0.0.2:646)
UDP: Hello
(1.0.0.4:1035 � 224.0.0.2:646)
UDP: Hello
(1.0.0.4:1035 � 224.0.0.2:646)
UDP: Hello
(1.0.0.2:1066 � 224.0.0.2:646)
UDP: Hello
(1.0.0.2:1066 � 224.0.0.2:646)MPLS_B
MPLS_A NO_MPLS_C
Neighbours Discovery (image)
GBS-MKT-Global-10_001Global Business Solutions SAL
• Frame mode:� New field is used for forwarding decisions
� Labels are advertised to reachable peers
• Packet mode:� Build routing table
� Each LSR assign label to every destination
� All LSR announce their labels
� Each LSR build its data structures (LIB, LFIB, FIB)• LIB: label table,
• FIB: forwarding table,
• LFIB: current label table
Label Distribution
GBS-MKT-Global-10_001Global Business Solutions SAL
LSR
Control Plane
Data Plane
OSPF:
RT:
LIB:
FIB:
LFIB:
OSPF: OSPF: 10.0.0.0/810.0.0.0/8 � 1.2.3.4
10.0.0.0/8 � 1.2.3.4
10.0.0.0/8 � 1.2.3.410.1.1.1
LDP: 3LDP: 10.0.0.0/8, L=3
L=5 10.1.1.1
10.0.0.0/8 � Next-hop L=3, Local L=5LDP: 5LDP: 10.0.0.0/8, L=5
L=3 10.1.1.1
L=3 10.1.1.1L=5 � L=3
, L=3
Label Distribution (image)
GBS-MKT-Global-10_001Global Business Solutions SAL
• IP routing table:� Tables are build based on the routing protocol (L3)
� FIB are build based on routing table with no labeling
• Allocating labels:� Each LSR allocates a label asynchronously (local
significance)
� LIB and LFIB setup, action “pop”
• Advertisement:� Each LSR advertise all its neighbors (up/down stream)
� ALL LSR store received label on LIB
� Edge LSR store label from their next-hop in FIB
� Every LSR insert outgoing labels in LFIB
Packet Propagation (1)
GBS-MKT-Global-10_001Global Business Solutions SAL
• Packet propagation:� IP lookup is done in FIB, packet labeled (ingress LSR)
� Labeled packet lookup is performed in LFIB, label switched
� Label lookup is performed on LFIB, label removed (egress LSR) if action is “pop”
• Advantages:� Liberal label retention improves convergence speed
Packet Propagation (2)
GBS-MKT-Global-10_001Global Business Solutions SAL
Building the IP Routing Table
– IP routing protocols are used to build IP routing tables on all LSRs.
– FIBs are built based on IP routing tables with no labeling information.
Network Next-hop
X B
Routing table of A
Network Next-hop
X C
Routing table of B
Network Next-hop
X D
Routing table of C
Network Next-hop
X C
Routing table of ENetwork Next hop Label
X B —
FIB on A
A B C D
E
Network X
Packet Propagation (image)
GBS-MKT-Global-10_001Global Business Solutions SAL
A B C D
E
Network X
Router B assigns label 25 to
destination X.
Packet Propagation (image)
Allocating Labels
– Every LSR allocates a label for every destination in the IP routing table.
– Labels have local significance.
– Label allocations are asynchronous.
Network Next-hop
X C
Routing table of B
GBS-MKT-Global-10_001Global Business Solutions SAL
A B C D
E
Network X
Router B assigns label 25 to
destination X.
Network LSR label
X local 25
LIB on BLocal label is stored in LIB.
Label Action Next hop
25 pop C
LFIB on B Outgoing action is pop, as B
has received no label for X
from C.
Packet Propagation (image)
LIB and LFIB Setup
– LIB and LFIB structures have to be initialized on the LSR allocating the label.
Network Next-hop
X C
Routing table of B
GBS-MKT-Global-10_001Global Business Solutions SAL
A B C D
E
Network X
Network LSR label
X local 25
LIB on B
X = 25X = 25
Packet Propagation (image)
Label Distribution
– The allocated label is advertised to all neighbor LSRs, regardless of whether the neighbors are upstream or downstream LSRs for the destination.
GBS-MKT-Global-10_001Global Business Solutions SAL
X = 25X = 25
Network LSR label
X B 25
LIB on ANetwork LSR label
X B 25
LIB on C
Network LSR label
X B 25
LIB on E
Network Next hop Label
X B 25
FIB on A
A B C D
E
Network X
Packet Propagation (image)
Receiving Label Advertisement
– Every LSR stores the received label in its LIB
– Edge LSRs that receive the label from their next-hop also store the label information in the FIB
GBS-MKT-Global-10_001Global Business Solutions SAL
IP: X Lab: 25 IP: X
Network Next hop Label
X B 25
FIB on A
IP lookup is performed in
FIB: packet is labeled.
Label Action Next hop
25 pop C
LFIB on B
Label lookup is performed
in LFIB: label is removed.
A B C
E
Packet Propagation (image)
Interim Packet Propagation
– Forwarded IP packets are labeled only on the path segments where the labels have already been assigned
GBS-MKT-Global-10_001Global Business Solutions SAL
Network LSR label
X B 25
local 47
LIB on C
Label Action Next hop
47 pop D
LFIB on C
A B C D
E
Network XRouter C assigns label
47 to destination X.
X = 47
Packet Propagation (image)
Further Label Allocation
– Every LSR will eventually assign a label for every destination
GBS-MKT-Global-10_001Global Business Solutions SAL
Network LSR label
X local 25
C 47
LIB on BNetwork Next hop Label
X C 47
FIB on B
Label Action Next hop
25 47 C
LFIB on B
A B C D
E
X = 47
Network X
Packet Propagation (image)
Populating LFIB
– Router B has already assigned a label to X and created an entry in the LFIB
– The outgoing label is inserted in the LFIB after the label is received from the next-hop LSR
GBS-MKT-Global-10_001Global Business Solutions SAL
IP: X IP: X
Ingress LSR Egress LSR
A B C
E
Lab: 25 Lab: 47
Network Next hop Label
X B 25
FIB on A
IP lookup is performed in
the FIB, packet is labeled.
Label Action Next hop
47 pop D
LFIB on C
Label lookup is performed
in the LFIB, label is removed.
Label Action Next hop
25 47 C
LFIB on B
Label lookup is performed
in the LFIB, label is switched.
Packet Propagation (image)
GBS-MKT-Global-10_001Global Business Solutions SAL
• Steady state: all LSR populated their LIB, LFIB and FIB
• Link failure:� entries are removed from data structure
� Rebuild the routing and forwarding tables
� LFIB & FIB rebuilt immediately from LIB
• Link recovery:� Routing protocols discovered
� IP routing tables rebuilt, as well FIB and LFIB
� Routing protocols optimize forwarding path
• Remarks:� End-to-end connectivity intermittently broken
� Traffic engineering (make-before-break) use
Convergence
GBS-MKT-Global-10_001Global Business Solutions SAL
Network Next-hop
X C
Routing table of BNetwork Next hop Label
X C 47
FIB on B
Network LSR label
X local 25
C 47
E 75
LIB on B
Label Action Next hop
25 47 C
LFIB on B
A B C D
E
Network X
Convergence (image)
Steady State Description
– After the LSRs have exchanged the labels, LIB, LFIB and FIB data structures are completely populated.
GBS-MKT-Global-10_001Global Business Solutions SAL
Network Next-hop
X C
Routing table of B
Network Next hop Label
X C 47
FIB on B
Network LSR label
X local 25
C 47
E 75
LIB on B
Label Action Next hop
25 47 C
LFIB on B
�A B C D
E
Network X
�
Convergence (image)
Link Failure Actions
– Routing protocol neighbors and LDP neighbors are lost after a link failure.
– Entries are removed from various data structures.
GBS-MKT-Global-10_001Global Business Solutions SAL
Network LSR label
X local 25
C 47
E 75
LIB on B
Label Action Next hop
25 47 C
LFIB on B
Network Next hop Label
X E —
FIB on BNetwork Next-hop
X E
Routing table of B
A B C D
E
Network X
�
Convergence (image)
Routing Protocol Convergence
– Routing protocols rebuild the IP routing table and the IP forwarding table.
GBS-MKT-Global-10_001Global Business Solutions SAL
Network LSR label
X local 25
C 47
E 75
LIB on B
Network Next-hop
X E
Routing table of B
Label Action Next hop
25 75 E
LFIB on B
Network Next hop Label
X E 75
FIB on B
A B C D
E
Network X
�
Convergence (image)
MPLS Convergence
– The LFIB and labeling information in the FIB are rebuilt immediately after the routing protocol convergence, based on labels stored in the LIB.
GBS-MKT-Global-10_001Global Business Solutions SAL
Network LSR label
X local 25
C 47
E 75
LIB on B
Network Next-hop
X E
Routing table of B
Label Action Next hop
25 75 E
LFIB on B
Network Next hop Label
X E 75
FIB on B
A B C D
E
Network X
Convergence (image)
Link Recovery Actions
– Routing protocol neighbors are discovered after link recovery.
GBS-MKT-Global-10_001Global Business Solutions SAL
Network LSR label
X local 25
C 47
E 75
LIB on B
Label Action Next hop
25 75 E
LFIB on B
Network Next hop Label
X E 75
FIB on BNetwork Next-hop
X E
Routing table of B
C C —
pop C
A B C D
E
Network X
Convergence (image)
IP Routing Convergence After Link Recovery
– IP routing protocols rebuild the IP routing table.
– The FIB and the LFIB are also rebuilt, but the label information might be lacking.
GBS-MKT-Global-10_001Global Business Solutions SAL
• Guidelines
• Examples
Implementation
GBS-MKT-Global-10_001Global Business Solutions SAL
• Implementation guidelines depends on:
� Size of the network
� Geographical distribution
� Service classification
� Projected level of availability
� Convergence speed requirements
Guidelines
GBS-MKT-Global-10_001Global Business Solutions SAL
CE
CE
P/PE
CE
P/PE
Example I
GBS-MKT-Global-10_001Global Business Solutions SAL
CECE
PE
CE
P/PE P/PE
Example II
GBS-MKT-Global-10_001Global Business Solutions SAL
CE CE
PE
CE
P P
CE CE
PEPE
Example III
GBS-MKT-Global-10_001Global Business Solutions SAL
L2/L3 MPLS Routing & Switching Audit
GBS-MKT-Global-10_001Global Business Solutions SAL
L2/L3 MPLS Audit
• Pre-Requisites & Deliverables
• Activities Description
• Case Studies
GBS-MKT-Global-10_001Global Business Solutions SAL
Pre-Requisites & Deliverables
• Pre-Requisites� Network Diagram: logical diagrams representing the physical and
logical connectivity of all IP based nodes in the transport layer
� Systems Configuration: collection of both high and low level data representing the running setup of all the nodes in question
� Logging information: only if quickly available, a history of 1 month would be fine, otherwise we will highlight major node to collect output from upon reception of the network diagram
• Deliverables� High level service delivery diagram
� End to end service availability, performance, security and capacity
� Nodes status, highlighting major issues and impact on the service
GBS-MKT-Global-10_001Global Business Solutions SAL
• Assessment� Facts findings (LLD collection)
� Running Configuration building simulation
� Availability, performance, security and capacity
• Recommendation� Quick wins solutions (low cost that induce big results)
� Pitfalls avoidance (potential issues or problems)
� Phased plan (with cost & time estimate)
Activities Description
GBS-MKT-Global-10_001Global Business Solutions SAL
• Availability� End to end service identifications
� Highlighting potential failure scenarios
� Convergence latency issues
• Performance� Per LSR analysis (utilization, log, etc…)
� End to end service classification analysis
� Convergence speed matching service requirements
Case Studies
GBS-MKT-Global-10_001Global Business Solutions SAL
A
C
B
Example
The MPLS domain carriers both voice and data traffic
– In this example, end users on B are communicating with peers/destination through A.
– If the link between A and B fails, all traffic will be routed through C.
– Even with proper dimensioning, both links B-C & C-A will be congested and the LSR C will be overloaded, thus performance issue.
– In order to remediate this issue, simply converge voice traffic quickly, delay data convergence until platform is stable, (possibly limit further voice and/or data calls) and prioritize important traffic.
Internet
Voice-2
Voice-1
Data-1
GBS-MKT-Global-10_001Global Business Solutions SAL
Thank You