1. MPLS fundamentals Sherif Toulan, P. Eng. ,CCIE#4220 Sr
MPLS fundamentals Sherif Toulan, P.Eng.,CCIE#4220 Sr. Technical Leader, Cisco Systems Canada

2. Agenda Topics MPLS Technology Basics MPLS Traffic Engineering (TE)
MPLS Layer-2 Virtual Private Networks (L2 VPN)
MPLS Layer-3 Virtual Private Networks (L3 VPN)
Summary

3. MPLS Technology Basics

4. Agenda Evolution of MPLS MPLS Reference Architecture MPLS forwarding
Summary

5. Evolution of MPLS Technology Evolution and Main Growth Areas
Evolved in 1996 to full IETF standard, covering over 130 RFCs
Key application initially were Layer-3 VPNs, followed by Traffic Engineering (TE), and Layer-2 VPNs
Optimize MPLS for packet transport
Optimize MPLS for video
Complete base MPLS portfolio
Bring MPLS to Market
First L3VPNs Deployed
First L2VPN Deployments
Large Scale L2VPN
Deployments
Cisco ships MPLS
First MPLS TE Deployments
Large Scale L3VPN
Deployments
Large Scale MPLS TE
Deployments
First MPLS Transport Profile Deployments
- A Request for Comments (RFC) is a publication of the Internet Engineering Task Force (IETF) and the Internet Society, the principal technical development and standards-setting bodies for the Internet.

6. What Is MPLS? Multi Protocol Label Switching
It’s all about labels …
Use the best of both worlds
Layer-2 (ATM/FR): efficient forwarding and traffic engineering
Layer-3 (IP): flexible and scalable
MPLS forwarding plane
Use of labels for forwarding Layer-2/3 data traffic
Labeled packets are being switched instead of routed
Leverage layer-2 forwarding efficiency
MPLS control/signaling plane
Use of existing IP control protocols extensions + new protocols to exchange label information
Leverage layer-3 control protocol flexibility and scalability
Multi
Multi-Protocol: The ability to carry any payload.
Have:IPv4, IPv6, Ethernet, ATM, FR.
Could do IPX, AppleTalk, DECnet, etc etc.
Protocol
Label
Uses Labels to tell a node what to do with a packet; separates forwarding (hop by hop behavior) from routing (control plane)
Switching
Routing == IPv4 or IPv6 lookup.
Then forwarding is based on label Switching.
-Multiprotocol Label Switching (MPLS) is a mechanism in high-performance telecommunications networks that directs data from one network node to the next based on short path labels rather than long network addresses, avoiding complex lookups in a routing table. The labels identify virtual links (paths) between distant nodes rather than endpoints. MPLS can encapsulate packets of various network protocols. MPLS supports a range of access technologies, including ATM, Frame Relay, and DSL.
-Telecommunication networks:
-Routing table:
-ATM :
-Frame Relay :
-DSL :
-IPX protocol
-DECnet protocol
-Asynchronous Transfer Mode “ATM”:
-Frame Relay

7. MPLS Reference Architecture
Different Type of Nodes & their Roles in a MPLS Network
P (Provider) router
Label switching router (LSR)
Switches MPLS-labeled packets
PE (Provider Edge) router
Label Edge router (LER)
Imposes and removes MPLS labels
CE (Customer Edge) router
Connects customer network to MPLS network, no labels to be sent to CE nodes
MPLS enabled Domain CE
Label switched traffic P PE
MPLS core
- P, PE nodes usually belong to the Service Provider who is offering the end customer MPLS Services.
- CE (customer Edge) are customer devices sending traffic to PE nodes
- CE devices do not understand MPLS

8. Basic MPLS Forwarding Operations
How Labels Are Being Used to Establish End-to-end Connectivity
Label imposition (Push)
By ingress PE router; classify and label packets
Based on Forwarding Equivalence Class (FEC)
Label swapping
By P router; forward packets using labels; indicates service class & destination
Label disposition (Pop)
By egress PE router; remove label and forward original packet to destination CE
MPLS enabled Domain
Label Imposition (Push)
Label Disposition (PoP)
Label Swap
Label Swap P P CE PE PE CE L1 L2 L3
MPLS core CE CE PE P P PE
- MPLS tutorial:
A FEC is a group/flow of packets that are forwarded along the same path and treating with the same with regards to forwarding treatment. All packets belonging to the same FEC have the same label. However not all the packets that have the same label belonging to the same FEC because their forwarding treatment could be different and they could belong to the different FEC. The router which decides which packets belong to which FEC is Ingress LSR.
“FEC = Set of all packets that are going to be forwarded in exactly the same way”

9. MPLS Label Entry (4 bytes) MPLS Label Stack (1 label)
Label Definition and Encapsulation
Labels used for making forwarding decision
Multiple labels (4 bytes) can be used for MPLS packet encapsulation
Outer label always used for switching MPLS packets in network
Inner labels usually used for services (e.g. Layer 2/Layer 3 VPN)
MPLS Label Entry (4 bytes)
Label = 20 bits
EXP S
TTL
EXP = Experimental Bits for QoS : 3 Bits; S = Bottom of Stack; TTL = Time to Live
Layer 2 MAC Header
MPLS Label
4 bytes
Layer 3 Packet
MPLS Label Stack (1 label)
- MPLS label is a short, four-byte, fixed-length, locally-significant identifier which is used to identify a Forwarding Equivalence Class (FEC). The label which is put on a particular packet represents the FEC to which that packet is assigned.
Label—Label Value (Unstructured), 20 bits
Exp—Experimental Use, 3 bits; currently used as a Class of Service (CoS) field.
S—Bottom of Stack, 1 bit
-The label is imposed between the data link layer (Layer 2) header and network layer (Layer 3) header. The top of the label stack appears first in the packet, and the bottom appears last. The network layer packet immediately follows the last label in the label stack.
Ethernet data:
MAC frame
MAC address

10. MPLS Path (LSP) Setup Traffic ForwardingIP
MPLS
Forwarding
Destination address based
Forwarding table learned from control plane
TTL support
Label based
Forwarding table learned from control plane
Control Plane
OSPF, IS-IS, BGP
LDP, RSVP
Packet Encapsulation
IP Header
One or more MPLS labels
QoS
8 bit TOS field in IP header
3 bit Traffic Class field in label
OAM
IP ping, traceroute
MPLS OAM
Label Switched Path (LSP) signaling
Either Label Distribution Protocol (LDP*) or RSVP for TE (traffic engineering)
Leverages IP routing Forwarding Information Base (FIB) table
Exchange of labels
Label bindings to IP addresses
Downstream MPLS node advertises what label to use to send traffic to node
MPLS forwarding
MPLS Forwarding table
The predetermined paths that make MPLS work are called label-switched paths (LSPs). Routers in an MPLS network exchange MPLS information to set up these paths for various source-destination pairs.
RSVP is a signaling protocol that reserves resources, The protocol was extended in MPLS RSVP TE to enable RSVP to set up label switched paths (LSPs) that can be used for TE in MPLS networks.
Operation,Administration and Maintenance (OAM) used for managing & troubleshooting the network:
Time to live (TTL):
Quality of service (QoS) :
* Label Distribution Protocol “LDP signaling assumed for next the examples”

11. MPLS Path (LSP) Setup Signaling Options
LDP
RSVP
Forwarding path
LSP
TE Tunnel
Primary and, optionally, backup
Forwarding Calculation
Based on IP routing database
Shortest-Path based
Based on TE topology database
Shortest-path and/or other constraints (CSPF calculation)
Packet Encapsulation
Single label
One or two labels
Signaling
By each node independently
Uses existing routing protocols/information
Initiated by head-end node towards tail-end node
Uses routing protocol extensions/information
Supports bandwidth reservation
Supports link/node protection
Label Distribution Protocol (LDP) signaling
Leverages existing routing
Can use both protocols simultaneously
They work differently, they solve different problems
Dual-protocol deployments are very common
- MPLS networks must have LDP enabled
If Traffic Engineering is enabled then RSVP is used for signaling TE tunnels
LDP does not need to be enabled with MPLS TE
Cont.

12. IP Packet Forwarding Example
Basic IP Packet Forwarding
IP Forwarding Table
IP routing information exchanged between nodes
Via IGP (e.g., OSFP, IS-IS)
Packets being forwarded based on destination IP address
Lookup in routing table
IP Forwarding Table
IP Forwarding Table …
128.89
171.69
Address
I/F 1 …
128.89
171.69
Address
I/F 1 …
128.89
171.69
Address
I/F 1 1
Data
Data 1
Data
Data 1
I/F = Interface port
IGP : Interior Gateway Protocol, i.e. routing protocol enabled to forward IP packets like OSPF (Open Shortest Path first), or ISIS Intermediate System to Intermediate System
Routers send packets toward their destination, by looking at the routing table & finding next hop to reach destination.
Routing protocols like OSPF (Open Shortest Path first), ISIS Intermediate System to Intermediate System (IS-IS) are used in core networks
Both IS-IS and OSPF are link state protocols, and both use the same Dijkstra algorithm for computing the best path through the network
Dijkstra algorithm

13. MPLS Path (LSP) Setup with LDP enabled
Step 1: IP Routing (IGP) Convergence
Enable IGP Routing (OSPF or ISIS) & MPLS LDP on all core links, i.e. PE-P & P-P links
Exchange of IP routes in core via:
OSPF, IS-IS….,etc.
Establish IP reachability
MPLS Forwarding Table
MPLS Forwarding Table
MPLS Forwarding Table In
Label
Address
Prefix
Out
I’face
Out
Label In
Label
Address
Prefix
Out
I’face
Out
Label In
Label
Address
Prefix
Out
I’face
Out
Label
128.89 1
128.89
128.89
171.69 1
171.69 1 … … … … … …
128.89 1
You Can Reach Thru Me
You Can Reach and
Thru Me 1
You Can Reach Thru Me
Routing Updates (OSPF, ISIS, …)
171.69
- IGP Routing protocol has to be enabled, i.e. OSPF or ISIS
- LDP has to be also enabled on all core links for MPLS before labels are advertised between nodes. If LDP is not enabled MPLS labels will not be built/advertised between core nodes
- Verify that reachability is achieved via ping or other means to ensure all IP subnets are advertised.

14. MPLS Path (LSP) Setup with LDP enabled
Step 2: Assignment of MPLS Labels
Local label mapping are sent to connected nodes
Receiving nodes update MPLS forwarding table
LDP label advertisement
MPLS Forwarding Table
MPLS Forwarding Table
MPLS Forwarding Table ) In
Label
Address
Prefix
Out
I’face
Out
Label In
Label
Address
Prefix
Out
I’face
Out
Label In
Label
Address
Prefix
Out
I’face
Out
Label -
128.89 1 20 20
128.89 30 30
128.89 - -
171.69 1 21 21
171.69 1 36 … … … … … … … … … … … …
128.89 1
Use Label 30 for
Use Label 20 for and
Use Label 21 for 1 1
Use Label 36 for
Label Distribution Protocol (LDP)
171.69
4- Labels are assigned to IP subnets & advertised via Label Distribution Protocol (LDP)

15. MPLS Traffic Forwarding with LDP
Step 3: Hop-by-hop Traffic Forwarding Using Labels
Ingress PE node adds label to packet (push)
Via MPLS forwarding table
Downstream node use label for forwarding decision (swap)
Outgoing interface
Out MPLS label
Egress PE removes label and forwards original packet (pop)
MPLS Forwarding Table
MPLS Forwarding Table
MPLS Forwarding Table In
Label
Address
Prefix
Out
I’face
Out
Label In
Label
Address
Prefix
Out
I’face
Out
Label In
Label
Address
Prefix
Out
I’face
Out
Label -
128.89 1 20 20
128.89 30 30
128.89 - -
171.69 1 21 21
171.69 1 36 … … … … … … … … … … … …
128.89 1
Data
Data 30 1
Data 20
Data
Forwarding based on Label
171.69
- PE nodes remove labels before sending to CE devices since they do not understand MPLS, only IP

16. MPLS Traffic Forwarding with LDP
Summary
MPLS technology is widely deployed in Service Provider core networks, MPLS increases the performance by doing forwarding based on labels
The MPLS enabled routers (LSRs, LERs) use Label Distribution Protocol (LDP) to assign & distributes labels.
The MPLS enabled routers advertise their labels to other MPLS enabled routers, the labels advertise reachability across MPLS network
Data packets are forwarded using MPLS labels hence increasing speed & performance in the Service Provider network
MPLS label is 4 bytes!

17. MPLS Traffic Engineering

18. Agenda MPLS Traffic Engineering (TE) motivation
MPLS TE Path Selection - Constraint-Based Shortest Path First (CSPF)
MPLS TE signaling – LSP Setup – Resource Reservation Protocol (RSVP)
Summary

19. Link Utilization problem with IGP (OSPF or ISIS)
PE1
PE3 P2
Cost= 20
Cost= 20 P3
40M P1
DS3
DS3
MPLS core
40M
PE2
OC3
Cost=20
PE4
Cost=10
DS3 P5 P4
DS3
Cost=20
IP (Mostly) Uses Destination-Based Least-Cost Routing
Flows from PE1, PE2 Merge at P1 and Become Indistinguishable
Upper path is overutilized!!
SPF algorithm is explained in the above link
Alternate Path Under-Utilized!!
IGP = Interior Gateway Protocol (OSPF or ISIS)

20. What MPLS-TE Addresses?
P1 is the HEADEND & sees all links
P1 computes paths on properties other than just shortest cost
No oversubscription!
Tunnel 0, Tunnel 1 are multi-hop tunnels
Node
Next-Hop
PE3
Tunnel0
PE4
Tunnel1
MPLS core P2
PE3
Tunnel 0
Tunnel 0
40Mb P1
OC3
40Mb P3
DS3
DS3
PE4
40Mb
40Mb
Tunnel 1
Tunnel 1
OC3
OC3
Tunnel 1
DS3 P4 P5
-Traffic engineering refers to the process of selecting the paths that traffic will transit through the network. Traffic engineering can be used to accomplish a number of goals. For example, a network organization could traffic engineer their network to ensure that none of the links or routers in the network are over or under utilized. Alternatively, a network organization could use traffic engineering to control the path taken by voice packets in order to ensure appropriate levels of delay, jitter, and packet loss. 
MPLS supports traffic engineering thus allowing network organizations to associate a Label-Switched Path (LSP) with whatever physical path they choose. MPLS also supports constraint-based routing, which ensures that an LSP can meet specific performance requirements. In addition, tools that work on a per-LSP basis allow network organizations to identify usage levels and plan accordingly.
DS3

21. TE Terminology HEADEND MIDPOINT TAILEND Upstream Downstream
Constraint-Based Shortest Path First (CSPF) only run by Headend
MPLS-TE uses CSPF to create a shortest path based on a series of constraints:
Resource Availability
User constraints ( tunnel priority,link attributes,metric,….etc.)
Tunnels are UNI-DIRECTIONAL!
HEADEND
MIDPOINT
TAILEND
Tunnel Direction
Upstream
Downstream
In normal SPF calculation process, a router places itself at the root of the tree with shortest paths to each of the destinations, only taking into account least metric (cost) to the destination. The process that generates a path for a TE tunnel to take is different from the regular SPF process. CSPF uses more than link cost to identify the probable paths that can be used for TE LSP paths. CSPF determines the best path to only the tunnel tailend router, not to all routers. Further, instead of just a single cost for a link between two neighbors, there's also bandwidth, link attributes and administrative weight. The decision as to which path is chosen to set up a TE LSP is performed at the headend router after ruling out all links that do not meet the bandwidth requirements in addition to the cost of the link. The result of the CSPF calculation is an ordered list of IP addresses that maps to the next-hop addresses of routers that form the TE LSP. CSPF takes the input from, both, user-specified path constraints and the information in TE database, before initiating the path computation.

22. TE Fundamentals – “Building Blocks”
Step 2:
CSPF does Path Calculation on headend only – uses IGP advertisements to compute “constrained” paths
Step 1:
Information Distribution - IGP (OSPF or ISIS) extensions used to flood bandwidth information between routers
Tunnel Headend
node
MPLS core
Tail
Midpoint
Step 3:
Path Setup-
RSVP/TE used to distribute labels, provide LAC, failure notification, etc.
MPLS TE tutorial:
&
another Good MPLS Traffic Engineering tutorial is at:
-Link Admission Control (LAC): Link admission control performs a check at each hop in the desired LSP path to see if the resources requested are available prior to TE tunnel creation. The link admission control function is performed on a per hop basis with each router in the LSP path checking resource availability. If the requested resources are available, bandwidth is reserved and the router waits for the RESERVATION message to confirm this resource allocation. If, however, the resources requested are unavailable, the IGP in use sends messages stating resource unavailability. Link admission control then informs RSVP about lack of resources, and RSVP sends PATHERR messages to the headend requesting the resources and notifying a lack of resources.

23. Path Calculation “Constraint-Based Shortest Path First (CSPF)”
Find shortest path to R8 with 8Mbps
MPLS
Additional link characteristics advertised by OSPF, ISIS TE extensions
Interface address
Physical bandwidth
Maximum reservable bandwidth
Administrative group (attribute flags)
IS-IS or OSPF flood link information
TE nodes build a topology database
CSPF uses topology database to find best path for TE
User Constraints and topology database used by CSPF as input to path computation
Tunnel can be signaled via RSVP once a path is found R1
(Headend) R8
(Tailend) 15 3 5 10 10 10 8 10
TE Topology database
Constrained Shortest Path First (CSPF) is an extension of shortest path algorithms. The path computed using CSPF is a shortest path fulfilling a set of constraints. It simply means that it runs shortest path algorithm after pruning those links that violate a given set of constraints. A constraint could be minimum bandwidth required per link (also known as bandwidth guaranteed constraint), end-to-end delay, maximum number of links traversed, include/exclude nodes. CSPF is widely used in MPLS Traffic Engineering. The routing using CSPF is known as Constraint Based Routing (CBR).
The path computed using CSPF could be exactly same as that of computed from OSPF and IS-IS, or it could be completely different depending on the set of constraints to be met. n
Link with insufficient bandwidth n
Link with sufficient bandwidth

24. IP/MPLS TE Path Setup using Resource Reservation Protocol (RSVP)
Tunnel signaled with TE extensions to RSVP
4 main RSVP messages for TE
RSVP PATH message
RSVP RESV message
RSVP error message (PATHERR,RESVERR)
RSVP tear messages (PATHTEAT,RESVTEAR)
Forwarding Table is populated using RSVP labels allocated by RESV messages
IP/MPLS
Head end
Tail end
RSVP Label=16
RESV
Mid point
PATH
TE LSP
RSVP is a signaling protocol that reserves resources, such as for IP unicast and multicast flows, and requests quality-of-service (QoS) parameters for applications. The protocol was extended in MPLS RSVP TE to enable RSVP to set up label switched paths (LSPs) that can be used for TE in MPLS networks. Once CSPF is completed, the path needs to be signaled across the network to establish a TE LSP and to consume resources across that path. RSVP (protocol type 46) is used to reserve resource throughout the network. Extensions were made to RSVP to allow RSVP to carry MPLS labels and other TE specifics. RSVP tries to signal the TE tunnel along the path from headend to tailend LSR. RSVP needs to signal it to get the label information set up at each LSR. RSVP also reserves bandwidth along the path.

25. How to map Customer Traffic into TE tunnel?
Multiple traffic selection options:
Static routes
Policy Based Routing
Traffic enters tunnel at head end
Head end
Customer Traffic
IP/MPLS
TE LSP
In computer networking, policy-based routing (PBR) is a technique used to make routing decisions based on policies set by the network administrator.
When a router receives a packet it normally decides where to forward it based on the destination address in the packet, which is then used to look up an entry in a routing table. However, in some cases, there may be a need to forward the packet based on other criteria. For example, a network administrator might want to forward a packet based on the source address, not the destination address. This should not be confused with source routing.
Policy-based routing may also be based on the size of the packet, the protocol of the payload, or other information available in a packet header or payload. This permits routing of packets originating from different sources to different networks even when the destinations are the same and can be useful when interconnecting several private networks.
Link:

26. MPLS Traffic Engineering Summary
Traffic Engineering (TE) tunnels are used to manipulate the traffic across the Service provider core networks
Traffic Engineering (TE) tunnels provide efficient utilization of links based on available bandwidth & defined user constraints.
Traffic Engineering (TE) tunnels use CSPF to establish the path & RSVP for signaling the TE tunnels
Customer traffic can be mapped to TE tunnels to follow a specific path across the core network & as defined in Service Level Agreements between Service Provider & Customer.

27. MPLS Layer-2 Virtual Private Network (L2 VPN)
Cisco Live 2014
4/16/2017
MPLS Layer-2 Virtual Private Network (L2 VPN)

28. Agenda Layer-2 Virtual Private Network (VPN) Technology Options
Virtual Private Wire Service (VPWS) overview
Summary

29. Layer 2 VPN (L2 VPN) Services to Customers
Cisco Live 2014
4/16/2017
Layer 2 VPN (L2 VPN) Services to Customers
Service to Customers
Layer-2 VPN
Point to Point services or Virtual Private Wire Services (VPWS) over MPLS
Service Provider sells the L2 VPN services to the end Customers (banks, dealers,….etc.)
Layer-3 VPNs
Layer-2 VPNs
Transport in the core network
MPLS (LDP/RSVP-TE) 
MPLS Forwarding 

30. Layer-2 Virtual Private Networks (L2 VPN)
Cisco Live 2014
4/16/2017
Layer-2 Virtual Private Networks (L2 VPN)
Technology Options- MPLS core
Virtual Private Wire Service (VPWS)
MPLS is required in the core
Point-to-point
Referred to as Pseudowires (PWs)
Virtual Private LAN Service (VPLS)
Multipoint relies on flooding
xEVPN
Multipoint with optimized routes learning
Optimized for load balancing, redundancy & scale
MPLS Layer-2 VPNs
Point-to-Point
Layer-2 VPNs (VPWS)
with MPLS core
Multipoint
Layer-2 VPNs (MPLS core)
xEVPN
VPLS
PBB-EVPN
EVPN

31. Packet Switched Network
Layer-2 VPN Enabler
The Pseudo wire
Ethernet
ATM
TDM
PPP/HDLC FR
Pseudo wire
Provider Edge (PE)
Packet Switched Network
L2 VPNs are built with Pseudo wire (PW) technology over MPLS networks
PWs provide a transport to multiple types of network services over a Packet Switched Network (PSN)
PW technology provides Like-to-Like transport and also Interworking (IW)
No routing is involved with Customers
Customers can run their own routing,QoS,security,….etc.
-Pseudo Wire (PW) Definition:
 Pseudo Wire (PW) is a mechanism that emulates the essential attributes of a telecommunications service (such as an ATM ,Frame Relay,…..etc.) over a Packet Switched Network (PSN). PW is intended to provide only the minimum necessary functionality to emulate the wire with the required degree of faithfulness for the given service definition.
-L2VPN PW is a Technology for tunneling L2 “circuits” (e.g. Ethernet, FR, ATM) through a packet network. When using L2VPN over MPLS network, Cisco uses the term AToM: Any Transport over MPLS
- HDLC is a bit-oriented synchronous data link layer protocol that was originally developed by the International Organization for Standardization (ISO).
- Point-to-Point Protocol (PPP) is a data link protocol used to establish a direct connection between two nodes. It can provide connection authentication, transmission encryption (using ECP, RFC 1968), and compression.
PPP is used over many types of physical networks including serial cable, phone line, trunk line, cellular telephone, specialized radio links, and fiber optic links such as SONET. PPP is also used over Internet access connections. Internet service providers (ISPs) have used PPP for customer dial-up access to the Internet, since IP packets cannot be transmitted over a modem line on their own, without some data link protocol. Two derivatives of PPP, Point-to-Point Protocol over Ethernet (PPPoE) and Point-to-Point Protocol over ATM (PPPoA), are used most commonly by Internet Service Providers (ISPs) to establish a Digital Subscriber Line (DSL) Internet service connection with customers.

32. Virtual Private Wire Service (VPWS) Overview
Cisco Live 2014
4/16/2017
Virtual Private Wire Service (VPWS)
Overview

33. Pseudo wire (PW) Reference Model
An Attachment Circuit (AC) is the physical or virtual circuit attaching a CE to a PE
Customer Edge (CE) equipment perceives a PW as an unshared link or circuit
Provides a point2point service
Discovery: Label Distribution Protocol (LDP)
Signaling: Label Distribution Protocol (LDP)
Emulated services can be:
Virtual Local Area Network (VLAN)
ATM
Frame Relay
HDLC/PPP
Emulated Layer-2 Service
Pseudo wire (PW)
PSN Tunnel
PE2
PE1
CE3
CE1
CE4
CE2
PW2
PW1
Native Service
AC (Ethernet)
AC (ATM)
-PW is an emulated circuit over IP or MPLS core
-Virtual Circuit(VC) is created for every Attachment Circuit (AC)
Goal is to transport Native Services without loosing original encapsulation format
-RFC 3985: PWE3 Architecture, March 2005
From the perspective of Customer Edge Equipment (CE), the PW is characterized as an unshared link or circuit
-Attachment Circuit (AC)
The physical or virtual circuit attaching a CE to a PE. An AC can be a Frame Relay DLCI, an ATM VPI/VCI, an Ethernet port, a VLAN, a HDLC link, a PPP connection on a physical interface, a PPP session from an L2TP tunnel, an MPLS LSP, etc.
-Customer Edge (CE)
A device where one end of a service originates and/or terminates. The CE is not aware that it is using an emulated service rather than a native service.
-Packet Switched Network (PSN)
Within the context of PWE3, this is a network using IP or MPLS as the mechanism for packet forwarding.
-Provider Edge (PE)
A device that provides PWE3 to a CE.
-Pseudo Wire (PW)
A mechanism that carries the essential elements of an emulated circuit from one PE to another PE over a PSN.
-Pseudo Wire Emulation Edge to Edge (PWE3)
A mechanism that emulates the essential attributes of a service (such as a T1 leased line or Frame Relay) over a PSN.
-PSN Tunnel
A tunnel across a PSN inside which one or more PWs can be carried.
Ref: RFC Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture

34. VPWS data forwarding Processing
Tunnel Label =45
VC Label= 28
Data traffic
Swap
Tunnel label swapping through MPLS cloud
Push tunnel label
Push data traffic label
Tunnel Label= 34
VC Label= 28
Data traffic
VC and Tunnel label imposition
Data traffic
Pop
VC label disposition
VC Label= 28
Data traffic
Data traffic
MPLS
CE-2
CE-1 P1 P2
PE1
PE2
Data Traffic direction
-PE nodes will push 2 labels, top label to switch data via MPLS & lower label corresponds to customer data.
-Last hop PE will pop customer data label & send traffic to customer without labels

35. Cisco Live 2014
4/16/2017
Summary
Layer-2 VPN enables transport of any traffic over MPLS network by a Service Provider core network
Layer-2 VPN is simple & Service Provider has no control or visibility in customer data
Label Distribution Protocol (LDP) is used for signaling & discovery between Provider Edge (PE) nodes
Typical applications of L2 VPN are layer-2 business VPN services & Data Center Interconnect
Customer Layer 2 traffic can be mapped onto a Traffic Engineering (TE) tunnel inside the Service Provider core network

36. MPLS Layer-3 Virtual Private Network (L3 VPN)
Cisco Live 2014
4/16/2017
MPLS Layer-3 Virtual Private Network (L3 VPN)

37. Agenda MPLS Layer-3 VPN (L3 VPN) fundamentals Summary Cisco Live 2014
4/16/2017
Agenda
MPLS Layer-3 VPN (L3 VPN) fundamentals
Summary

38. Layer-3 VPN vs. Layer-2 VPN
Customer end points peer with providers’ routers at Layer 3, i.e. there is routing protocol between Customer & Service Provider
Provider network responsible for distributing routing information to VPN sites
Don’t have to manually fully mesh customer endpoints to support any-to-any connectivity
Layer 2 VPNs
Customer endpoints connected via Layer 2 such as Frame Relay, ATM, Ethernet,….etc. connection
Provider network is not responsible for distributing site routers as routing relationship is between the customer endpoints
Provider will need to manually fully mesh end points if any-to-any connectivity is required

39. MPLS Layer-3 VPN Control Plane Basics
CE3
iBGP—VPNv4
Label Exchange
CE4
VRF1
VRF1 P1 P2
PE3
PE1
VRF2
LDP
LDP
VRF2
LDP
PE2
CE1
CE2
VPN service is enabled on PEs (VRFs are created and applied to VPN site interface)
VPN site’s CE1 connects to a VRF enabled interface on a PE1
VPN site routing by CE1 is distributed to MP-iBGP on PE1
PE1 allocates VPN label for each prefix, sets itself as a next hop and relays VPN site routes to PE3
PE3 distributes CE1’s routes to CE2 (Similar happens from CE2 side…)

40. MPLS Layer-3 VPN Packet Forwarding
Cisco Live 2014
4/16/2017
MPLS Layer-3 VPN Packet Forwarding
Lookup of destination IP address in VRF table
VPN label pushed
MPLS label pushed 2
IP packet
VPN label
Pop MPLS
top label 5
IP packet
VPN label
MPLS label
Labeled packet forwarded 3
Lookup of VPN
label in VRF table 6
IP packet
Packet forwarded as IP packet 7
IP packet
IP packet enters PE on VRF interface 1
Bank of Amercia
Bank of Amercia CE CE
VRF interface
VRF interface PE P PE
P swaps MPLS label 4
Site A
Site B
MPLS VPN Service Provider Network

41. The Full MPLS integrated Network: Layer-3 VPN, Layer-2 VPN, Traffic Engineering technologies
Traffic Engineering for Bandwidth protection and restoration
Layer 3 Routing protocols available on PE-CE – Static, RIPv2, OSPF, EIGRP, eBGP
Layer 3 Routing protocols available on PE-CE – Static OSPF,BGP
Internet CE
Internet
Gateway
MPLS Backbone CE PE PE CE CE
Layer 2 Circuits available – Ethernet, ATM, Frame Relay, PPP, HDLC
Layer 2 Circuits available – Ethernet, ATM, Frame Relay, PPP, HDLC
Legend
Virtual Leased Line,
SP deploy once and deliver many services
Enterprise – a set of equipment and many services
Layer 3 VPN
Layer 2 VPN
Traffic Engineering

42. MPLS session Key Takeaways
Cisco Live 2014
4/16/2017
MPLS session
Key Takeaways
MPLS networks consist of PE routers at ingress/egress and P routers in the core
MPLS forwarding operations is based on MPLS labels, hence it speeds up the performance
Label Distribution Protocol (LDP) is used for MPLS signaling
Routing protocols (OSPF or ISIS ) enabled in the core network has to be working properly for proper MPLS forwarding operation
Traffic Engineering manipulates that path of traffic to better utilize bandwidth & meet Service Level agreements between Service Provider & Customer
RSVP is used for TE signaling
Layer 3 VPN requires routing between Customer sites & Service Provider
Layer 2 VPN does not require routing between Customer sites & Service Provider
MPLS & its associated technologies are widely deployed across both Service Provider & Enterprise networks

43. Cisco Live 2014
4/16/2017

44. Acronyms Cisco Live 2014 4/16/2017 Acronym Description Acronym
MPLS
Multi Protocol label switching TE
Traffic Engineering
VPN
Virtual Private Network
ATM
Asynchronous transfer mode FR
Frame relay IP
Internet protocol
FEC
Forwarding equivalence class
LDP
Label distribution protocol
LSP
Label switched path
TOS
Type of service
RSVP
Resource reservation protocol
OAM
Operation, administration, maintenance
BGP
Border gateway protocol
TTL
Time to live
QoS
Quality of service
IGP
Interior gateway protocol
OSPF
Open shortest path first
MAC
Media Access Control
LAC
Link Admission Control
Acronym
Description
ISIS
Intermediate system to intermediate system
LSR
Label switch router
LER
Label edge router
CSPF
Constraint-based shortest path first
PBR
Policy based routing PW
Pseudowire
VPLS
Virtual private LAN service
VPWS
Virtual private wire service
EVPN
Ethernet Virtual Private Network
PBB-EVPN
Provider backbone bridging Ethernet Virtual Private Network
PSN
Packet Switched network
VLAN
Virtual local area network
HDLC
High-level data link control
PPP
Point-to-point protocol
IGP
Interior gateway protocol
RIPv2
Routing information protocol version 2
EIGRP
Enhanced Interior Gateway Routing Protocol
OAM
Operation, Administration & Maintenance