MPLS MultiProtocol Label Switching. Overview Drawbacks of Traditional IP Routing Basic MPLS Concepts MPLS Labels Traffic Engineering with MPLS.
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MPLSMPLS
MultiProtocol Label Switching
OverviewOverview
Drawbacks of Traditional IP Routing
Basic MPLS Concepts
MPLS Labels
Traffic Engineering with MPLS
MPLS Architecture
Routing protocols are used to distribute Layer 3 routing information.
Forwarding is based on the destination address only.
Routing lookups are performed on every hop.
Drawbacks of Traditional IP Drawbacks of Traditional IP ForwardingForwarding
Drawbacks of Traditional IP Forwarding Drawbacks of Traditional IP Forwarding (Cont.)(Cont.)Traditional IP ForwardingTraditional IP Forwarding
Every router may need full Internet routing information (more than 100,000 routes).
Drawbacks of Traditional IP Forwarding Drawbacks of Traditional IP Forwarding (Cont.)(Cont.)Traditional IP ForwardingTraditional IP Forwarding
Every router may need full Internet routing information (more than 100,000 routes).
Destination-based routing lookup is needed on every hop.
Most traffic goes between large sites A and B, and uses only the primary link.
Destination-based routing does not provide any mechanism for load balancing across unequal paths.
Drawbacks of Traditional IP Forwarding Drawbacks of Traditional IP Forwarding (Cont.) (Cont.) Traffic EngineeringTraffic Engineering
Basic MPLS ConceptsBasic MPLS Concepts
MPLS is a new forwarding mechanism in which packets are forwarded based on labels.
Labels usually correspond to IP destination networks (equal to traditional IP forwarding).
Labels can also correspond to other parameters, such as QoS or source address.
MPLS was designed to support forwarding of other protocols as well.
Basic MPLS Concepts (Cont.)Basic MPLS Concepts (Cont.) ExampleExample
Basic MPLS Concepts (Cont.)Basic MPLS Concepts (Cont.) ExampleExample
• Only edge routers must perform a routing lookup.
Basic MPLS Concepts (Cont.)Basic MPLS Concepts (Cont.) ExampleExample
• Only edge routers must perform a routing lookup.
• Core routers switch packets based on simple label lookups and swap labels.
Traffic Engineering with MPLSTraffic Engineering with MPLS
Traffic can be forwarded based on other parameters (QoS, source, ...).
Load sharing across unequal paths can be achieved.
SHIM LayerSHIM Layer
N
D
P
3
2
1
MPLS
MPLS LabelsMPLS Labels
MPLS technology is intended to be used anywhere regardless of Layer 1 media and Layer 2 protocol.
MPLS uses a 32-bit label field that is inserted between Layer 2 and Layer 3 headers
MPLS Labels (Cont.) MPLS Labels (Cont.) Label FormatLabel Format
MPLS uses a 32-bit label field that contains the following information: 20-bit label 3-bit experimental field 1-bit bottom-of-stack indicator 8-bit TTL field
MPLS Label StackMPLS Label Stack
Protocol identifier in a Layer 2 header specifies that the payload starts with a label (labels) and is followed by an IP header.
Bottom-of-stack bit indicates whether the next header is another label or a Layer 3 header.
If s=0, then label stack implementation is in use.
If s=1, then last label
Receiving router uses the top label only.
MPLS Label StackMPLS Label Stack (Cont.) (Cont.)
Usually only one label is assigned to a packet.
The following scenarios may produce more than one label: MPLS VPNs (two labels: The top label points to the
egress router and the second label identifies the VPN.)
MPLS TE (two or more labels: The top label points to the endpoint of the traffic engineering tunnel and the second label points to the destination.)
MPLS VPNs combined with MPLS TE (three or more labels.)
MPLS Labels (Cont.)MPLS Labels (Cont.)
MPLS Labels (Cont.)MPLS Labels (Cont.)
Some MPLS Terms...Some MPLS Terms...
FEC - Forward Equivalence Class LER - Label Edge Router LSR - Label Switch Router Label – 20 bit value Label Stack - Multiple labels containing
information on how a packet is forwarded. Label Switch Path - path that a packet
follows for a specific FEC LDP - Label Distribution Protocol, used to
distribute Label information between MPLS-aware network devices
•A packet can be mapped to a particular FEC based on the following criteria:
- Destination IP address- Source IP address
- TCP/UDP port- Class of service,- Application used etc…
Any combination of the previous criteria.
FEC
Label Switch RoutersLabel Switch Routers
LSR primarily forwards labeled packets (label swapping).
Edge LSR primarily labels IP packets and forwards them into the MPLS domain, or removes labels and forwards IP packets out of the MPLS domain.
Label Switch Routers (Cont.) Label Switch Routers (Cont.) Architecture of LSRsArchitecture of LSRs
LSRs, regardless of the type, perform these functions:
Exchange routing information
Exchange labels
Forward packets
The first two functions are part of the control plane.
The last function is part of the data plane.
LSPLSP
Label-Switched Path Simplex L2 tunnel across a network Concatenation of one or more label switched hops Analogous to an ATM PVC
New DelhiNew Delhi
MumbaiMumbai
LSPLSP
LSRLSR
MPLS enabled router is called label Switching Router Forwards MPLS packets using label-switching Executes one or more IP routing protocols Participates in MPLS control protocols
New DelhiNew Delhi
MumbaiMumbai
LSPLSP
LSRLSR
LSRLSR
LSRLSRLSRLSR
MPLS TerminologyMPLS Terminology
SanSanFranciscoFrancisco
New New YorkYork
LSPLSP
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
IngressIngressLSRLSR TransitTransit
LSRLSR TransitTransitLSRLSR
EgressEgressLSRLSR
MPLS Label Assignment/BindingMPLS Label Assignment/Binding
Assign labelLabel
assignedDataData
Control
Data
Control
Upstream Node
Downstream Node
Label Request for FEC10.0.0.0
MPLS Label Assignment/BindingMPLS Label Assignment/Binding
UpstreamUpstreamLDP peerLDP peer
DownstreamDownstreamLDP peerLDP peerLSRLSR
325413
Net: 10.0.0.0 Net: 10.0.0.0 Label: 52Label: 52
(3, 29)
Net: Net: 10.0.0.0 10.0.0.0 Label: 29Label: 29
MPLS TableMPLS TableIn Out
(2, 52)
MPLS TableMPLS TableIn Out
(1, 17)
MPLS TableMPLS TableIn Out
(5, 52)
ReceiveReceiveoutgoingoutgoing
labellabel(4, 17)
Net: 10.0.0.0 Net: 10.0.0.0
Label: 17Label: 17
AdvertiseAdvertiseincomingincoming
labellabel(3, 35)
Label OperationsLabel Operations
Label PushingLabel Pushing
S0
S1
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2
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Routing Information Base
Receive Logic Transmit Logic
Input port Output port
Forwarding Information Base
MPLS
Ingress Node
DH4H3H2 T2
DH4H3
101001001 11S
DH4H3H2 T2S
DH4H3S
101001001 11
DH4H3
Label SwappingLabel Swapping
S0
S1
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3
2
1
Routing Information Base
Receive Logic Transmit Logic
Input port Output port
Forwarding Information Base
MPLS
Transit Node
101001001 11S
DH4H3S
101001001 11S
DH4H3H2 T2S
DH4H3S
DH4H3H2 T2S
Label PoppingLabel Popping
S0
S1
N
D
P
3
2
1
Routing Information Base
Receive Logic Transmit Logic
Input port Output port
Forwarding Information Base
MPLS
Egress Node
DH4H3H2 T2S
101001001 11
DH4H3H2 T2
101001001 11S
DH4H3
DH4H3S
DH4H3
Label databasesLabel databases
LSR OperationLSR Operation
Each LSR maintains a connection table
Port 1
Port 3
Port 2
Port 4
Connection TableConnection TableIn
(port, label)Out
(port, label)
(1, 22)
(1, 24)
(1, 25)
(2, 23)
(2, 17)
(3, 17)
(4, 19)
(3, 12)
LabelOperation
Swap
Swap
Swap
Swap
25IP
19IP
1 2Ingress Routing TableIngress Routing TableDestination Next Hop
134.5/16
200.3.2/24
(2, 84)
(3, 99)
MPLS TableMPLS TableIn Out
(2, 84) (6, 0)
MPLS TableMPLS TableIn Out
(1, 99) (2, 56)
MPLS TableMPLS TableIn Out
(3, 56) (5, 0)
3 5
2
3
2 6134.5.1.5134.5.1.5
200.3.2.7200.3.2.7200.3.2.1200.3.2.1
134.5.6.1134.5.6.1
DestinationEgress Routing TableEgress Routing Table
Next Hop
134.5/16
200.3.2/24
134.5.6.1
200.3.2.1
200.3.2.7
MPLS Forwarding Example MPLS Forwarding Example
200.3.2.7
9999200.3.2.7 00200.3.2.7
200.3.2.75656200.3.2.7
MPLS ArchitectureMPLS Architecture
MPLS has two major components: Control plane: Exchanges Layer 3 routing
information and labels
Data plane: Forwards packets based on labels
Control plane contains complex mechanisms to exchange routing information, such as OSPF, EIGRP, IS-IS, and BGP, and to exchange labels, such as TDP, LDP, BGP, and RSVP.
Data plane has a simple forwarding engine.
MPLS Architecture (Cont.)MPLS Architecture (Cont.)
Router functionality is divided into two major parts: control plane and data plane
MPLS Architecture (Cont.)MPLS Architecture (Cont.)
Router functionality is divided into two major parts: control plane and data plane
MPLS Architecture (Cont.)MPLS Architecture (Cont.)
Router functionality is divided into two major parts: control plane and data plane
MPLS Architecture (Cont.)MPLS Architecture (Cont.)
Router functionality is divided into two major parts: control plane and data plane
MPLS Architecture (Cont.)MPLS Architecture (Cont.)
Router functionality is divided into two major parts: control plane and data plane
Network Architecture of Project 1Network Architecture of Project 1
Depending on the traffic expectations, the locations are divided into two categories, A & B.
A locations are provided with core routers.
B locations are provided with only edge routers.
Location ALocation A
A is further divided into four categories viz A1, A2, A3, A4
All A nodes are provided with Cisco routers.
BSNL NIB-II CORE ROUTER A1,A2,A3 &A4 CONNECTIVITY DIAGRAM
STM-16 LINK
STM-1 LINK
SiSi
CISCO ROUTER
JUNIPER ROUTER(Existing with BSNL)
LEGENDS
Jullundar
Jaipur
Pune
Ahmedabad
Indore
Lucknow
Patna
Noida
Kolkata
ChennaiBanglore
Mumbai
Ernakulam
Hyderabad
SiSi
Chandigarh
SiSi
Manglore
SiSi
Nagpur
SiSi
Vijaywada
SiSi
Raipur
SiSi
Coimbtore
SiSi
Bhubneshwar
SiSi
Ranchi
SiSi
Guwahati
SiSi
Allahabad
A1 Nodes - 5
A2+A3 Nodes - 9
A4 Nodes - 10
B NodesB Nodes
B locations are divided into B1 & B2 categories.
Provided with only edge routers Cisco 7613
B1 & B2 are dual homed to nearest A node on STM-1 link.
NIB-II A1,A2,A3,A4,B1& B2 ROUTER CONNECTIVITY DIAGRAM
A1 Nodes - 5
A2+A3 Nodes - 9
A4 Nodes - 10
B1 + B2 Nodes - 47
Jullundar
Jaipur
Pune
Ahmedabad
Indore
Lucknow
Patna
Noida
Kolkata
ChennaiBanglore
Mumbai
Ernakulam
Hyderabad
Chandigarh
Manglore
SiSi
Bhubneshwar
SiSi
Ranchi
Allahabad
SiSi
Coimbtore
Madurai
Trichy
Palghat
TrivandrumTrichur
Kalikat
SiSi
Vijaywada
Rajmundary
Vizag
Tirupati
Durgapur
Siliguri
DimapurSiSi
Guwahati
Kalyan
Panjim
Aurangabad
Kolhapur
Nashik
SiSi
Nagpur
Bhopal
Gwalior
Mehsana
Ambala Faridabad Gurgaon
Meerut
Agra
Dehradun
Ludhiana
Ferozpur
Shimla
Amritsar
SiSi
SiSi
Ajmer Jodhpur
MysoreHubli
Jamshedpur
Surat
Vadodara
Rajkot
Jabalpur
Shilong
Ghaziabad Noida
Varanasi Kanpur
Pondicherry
Belgaum
SiSi
Raipur
SiSi
Chennai
Ernakulam
Hyderabad
Pune
Indore
Ahmedabad
Jaipur Jallandar Lucknow
Patna
Kolkata
Noida
Mumbai
Bangalore
1
3
NIB - II Core Router
IXP Router Route Reflector
IDC Router
IGW Router
Routers ConnectivityRouters Connectivity
51
ReviewReview
Drawbacks of Traditional IP Routing
Basic MPLS Concepts
MPLS Labels
MPLS Architecture
Label Switch Routers
Label database
Label operations
Thank YouThank You
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