Information Technology Reference
In-Depth Information
used to guarantee bandwidth. MPLS can run on many L2 technologies, including ATM,
Frame Relay, PPP, Packet over SONET (POS), and Ethernet.
MPLS is an economical solution that can be easily integrated over any existing infrastruc-
ture offering flexibility because MPLS is independent of access technologies. SPs can of-
fer intelligent net work s er v ice s to their c u stomer s over a s ingle infrast r uc t ure. E ach of the
SP's customers can have one or more VPNs within the overall MPLS network, called vir-
tual routing and forwarding (VRF) instances.
MPLS Layer 3 Design Overview
MPLS Layer 3 VPNs have the following characteristics:
The MPLS network distributes labels to each VPN.
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Only labels for other VPN members are distributed.
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Each VPN is automatically provisioned by IP routing.
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Each MPLS network is as secure as Frame Relay connections.
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Encryption can be added to the VPN to provide privacy.
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Only one label for both for QoS and VPN is needed.
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MPLS Layer 3 VPNs represent the most popular deployed MPLS technology. MPLS Layer
3 VPNs leverage Border Gateway Protocol (BGP) to distribution VPN-related information.
The SP typically manages the BGP routing domain within the MPLS cloud. This can sig-
nificantly reduce the operational costs and complexities for enterprise environments.
Inside the MPLS cloud, network routes are learned with a dynamic Interior Gateway Pro-
tocol (IGP) routing protocol such as Open Shortest Path First (OSFP) Protocol, Enhanced
Interior Gateway Routing Protocol (EIGRP), Border Gateway Protocol (BGP), or with
static routes that are manually configured.
MPLS VPNs use labels to specify the VRF and the corresponding VPN destination net-
works, which prevent the overlapping of addresses between VPNs. With MPLS Layer 3
VPNs, other valued-added services can be layered on such as QoS and traffic engineering.
These services might offer enhanced network services such as voice, video, and data, for
example. In addition, MPLS TE and Fast Reroute (FRR) features can be used to provide
“tight service level agreements (SLA),” including up to five levels of QoS SLAs.
VPN Benefits
The major benefits of using VPNs are flexibility, cost, and scalability. VPNs are easy to set
up and deploy over existing infrastructure in most cases. VPNs enable network access to
remote users, remote sites, and extranet business partners. VPNs lower the cost of owner-
ship by reducing the WAN recurring monthly charges and standardizing VPN security
policies. The geographic coverage of VPNs is nearly everywhere Internet access is avail-
cause they can be deployed in a secure consistent manner.
