1.The MPLS labels are advertised between routers so that they can build a label-to-label mapping.
The label switching technique is not new. Frame Relay and ATM use it to move frames or cells
throughout a network
Benefits of MPLS
■ The use of one unified network infrastructure
■ Better IP over ATM integration
■ Border Gateway Protocol (BGP)-free core
■ The peer-to-peer model for MPLS VPN
■ Optimal traffic flow
■ Traffic engineering
The Use of One Unified Network Infrastructure
With MPLS, the idea is to label ingress packets based on their destination address or other
preconfigured criteria and switch all the traffic over a common infrastructure. This is the great
advantage of MPLS
By using MPLS with IP, you can extend the possibilities of what you can transport. Adding labels
to the packet enables you to carry other protocols than just IP over an MPLS-enabled Layer 3 IP
backbone, similarly to what was previously possible only with Frame Relay or ATM Layer 2
networks. MPLS can transport IPv4, IPv6, Ethernet, High-Level Data Link Control (HDLC), PPP,
and other Layer 2 technologies.
The feature whereby any Layer 2 frame is carried across the MPLS backbone is called Any
Transport over MPLS (AToM).
BGP-Free Core
MPLS, enables the forwarding of packets based on a label lookup rather than a lookup
of the IP addresses. MPLS enables a label to be associated with an egress router rather than with
the destination IP address of the packet. The label is the information attached to the packet that
tells every intermediate router to which egress edge router it must be forwarded. The core routers
no longer need to have the information to forward the packets based on the destination IP address.
Thus, the core routers in the service provider network no longer need to run BGP.
"The label that is associated with an IP packet is the label that is associated with this
BGP next-hop IP address."
An Internet service provider (ISP) that has 200 routers in its core network needs to have BGP
running on all 200 routers. If MPLS is implemented on the network, only the edge routers—which
might be 50 or so routers—need to run BGP
Peer-to-Peer VPN Model
In the peer-to-peer VPN model, the service provider routers carry the customer data across the
network, but they also participate in the customer routing. In other words, the service provider
routers peer directly with the customer routers at Layer 3
Before MPLS existed, the peer-to-peer VPN model could be achieved by creating the IP routing
peering between the customer and service provider routers. The VPN model also requires
privateness or isolation between the different customers.ACL can be used for privateness.
Before MPLS came into being, the overlay VPN model was deployed much more commonly than
the peer-to-peer VPN model
MPLS VPN is one application of MPLS that made the peer-to-peer VPN model much easier to implement.The privateness in MPLS VPN networks is achieved by using the concept of virtual routing/ forwarding (VRF)
Traffic Engineering
The basic idea behind traffic engineering is to optimally use the network infrastructure, including
links that are underutilized, because they do not lie on the preferred path , With traffic engineering
implemented in the MPLS network, you could have the traffic that is destined for a particular
prefix or with a particular quality of service flow from point A to point B along a path that is
different from the least-cost path.
History of MPLS in Cisco IOS
Cisco Systems started off with putting labels on top of IP packets in what was then called tag
switching. The first implementation was released in Cisco IOS 11.1(17)CT in 1998. A tag was the name for what is now known as a label. This implementation could assign tags to networks from the routing table and put those tags on top of the packet that was destined for that network
IETF standardized tag switching into MPLS. The IETF released the first RFC on
MPLS—RFC 2547, “BGP/MPLS VPNs”—in 1999.
The label switching technique is not new. Frame Relay and ATM use it to move frames or cells
throughout a network
Benefits of MPLS
■ The use of one unified network infrastructure
■ Better IP over ATM integration
■ Border Gateway Protocol (BGP)-free core
■ The peer-to-peer model for MPLS VPN
■ Optimal traffic flow
■ Traffic engineering
The Use of One Unified Network Infrastructure
With MPLS, the idea is to label ingress packets based on their destination address or other
preconfigured criteria and switch all the traffic over a common infrastructure. This is the great
advantage of MPLS
By using MPLS with IP, you can extend the possibilities of what you can transport. Adding labels
to the packet enables you to carry other protocols than just IP over an MPLS-enabled Layer 3 IP
backbone, similarly to what was previously possible only with Frame Relay or ATM Layer 2
networks. MPLS can transport IPv4, IPv6, Ethernet, High-Level Data Link Control (HDLC), PPP,
and other Layer 2 technologies.
The feature whereby any Layer 2 frame is carried across the MPLS backbone is called Any
Transport over MPLS (AToM).
BGP-Free Core
MPLS, enables the forwarding of packets based on a label lookup rather than a lookup
of the IP addresses. MPLS enables a label to be associated with an egress router rather than with
the destination IP address of the packet. The label is the information attached to the packet that
tells every intermediate router to which egress edge router it must be forwarded. The core routers
no longer need to have the information to forward the packets based on the destination IP address.
Thus, the core routers in the service provider network no longer need to run BGP.
"The label that is associated with an IP packet is the label that is associated with this
BGP next-hop IP address."
An Internet service provider (ISP) that has 200 routers in its core network needs to have BGP
running on all 200 routers. If MPLS is implemented on the network, only the edge routers—which
might be 50 or so routers—need to run BGP
Peer-to-Peer VPN Model
In the peer-to-peer VPN model, the service provider routers carry the customer data across the
network, but they also participate in the customer routing. In other words, the service provider
routers peer directly with the customer routers at Layer 3
Before MPLS existed, the peer-to-peer VPN model could be achieved by creating the IP routing
peering between the customer and service provider routers. The VPN model also requires
privateness or isolation between the different customers.ACL can be used for privateness.
Before MPLS came into being, the overlay VPN model was deployed much more commonly than
the peer-to-peer VPN model
MPLS VPN is one application of MPLS that made the peer-to-peer VPN model much easier to implement.The privateness in MPLS VPN networks is achieved by using the concept of virtual routing/ forwarding (VRF)
Traffic Engineering
The basic idea behind traffic engineering is to optimally use the network infrastructure, including
links that are underutilized, because they do not lie on the preferred path , With traffic engineering
implemented in the MPLS network, you could have the traffic that is destined for a particular
prefix or with a particular quality of service flow from point A to point B along a path that is
different from the least-cost path.
History of MPLS in Cisco IOS
Cisco Systems started off with putting labels on top of IP packets in what was then called tag
switching. The first implementation was released in Cisco IOS 11.1(17)CT in 1998. A tag was the name for what is now known as a label. This implementation could assign tags to networks from the routing table and put those tags on top of the packet that was destined for that network
IETF standardized tag switching into MPLS. The IETF released the first RFC on
MPLS—RFC 2547, “BGP/MPLS VPNs”—in 1999.
OLD
Terminology
|
New Terminology
|
Tag
Switching
|
MPLS
|
Tag
|
Label
|
TDP(Tag
Distribution Protocol)
|
LDP
(Label Distr. Pro.)
|
TFIB(Tag
forwarding Information base)
|
LFIB(
Label FIB)
|
TSR
( Tag switching router)
|
LSR
( Label Switching Router)
|
TSP ( Tag switched Path)
|
LSP ( Label Switched Path)
|
TSC(Tag switch controller)
|
LSC ( Label switch controller)
|
TDP was used as the basis for LDP. LDP has the same functionality as TDP, but they are different protocols.
Architectural Blocks of MPLS
MPLS functionality on Cisco devices is divided into two main architectural blocks:
Control plane— Performs functions related to identifying reachability to destination prefixes. Therefore, the control plane contains all the Layer 3 routing information, as well as the processes within, to exchange reachability information for a specific Layer 3 prefix. Common examples of control plane functions are routing protocol information exchange like in OSPF and BGP. . In addition, all protocol functions that are responsible for the exchange of labels between neighboring routers function in the control plane as in label distribution protocols
Data plane— Performs the functions relating to forwarding data packets. These packets can be either Layer 3 IP packets or labeled IP packets. i.e FIB/LFIB
Architectural Blocks of MPLS
MPLS functionality on Cisco devices is divided into two main architectural blocks:
Control plane— Performs functions related to identifying reachability to destination prefixes. Therefore, the control plane contains all the Layer 3 routing information, as well as the processes within, to exchange reachability information for a specific Layer 3 prefix. Common examples of control plane functions are routing protocol information exchange like in OSPF and BGP. . In addition, all protocol functions that are responsible for the exchange of labels between neighboring routers function in the control plane as in label distribution protocols
Data plane— Performs the functions relating to forwarding data packets. These packets can be either Layer 3 IP packets or labeled IP packets. i.e FIB/LFIB
MPLS Applications
1.MPLS VPN
2.MPLS TE(Traffic Engineering)
3.AToM( Any Transport over MPLS):-
Layer 2 encapsulation types that can be carried over an AToM network today are Frame Relay, ATM, PPP, HDLC, Ethernet, and 802.1Q.
4.Virtual Private LAN Service.
VPLS is the Layer 2 service that emulates a LAN across an MPLS-enabled network
No comments:
Post a Comment