MPLS is a protocol for speeding up the forwarding of packets through a network. It does this by labelling the packets with short, fixed-length tags. The labels are used to identify the next hop that the packet should be forwarded to, and they are removed at each hop. This allows the network to quickly forward packets without having to do a routing lookup at each hop.
MPLS is most commonly used in networks that carry voice and video traffic, where the goal is to minimize delay and jitter. It can also be used in data networks, where the goal is to reduce congestion or improve performance.
Note: MPLS works between layer 2 and layer 3 of the OSI model.
The Working of MPLS Network
Here are the steps involved in how MPLS works:
1. A router receives a packet from a host on the network.
2. The router looks up the destination address in its forwarding table to find the next hop that the packet should be sent to.
3. The router encapsulates the packet in an MPLS header and forwards it to the next hop.
4. The next hop router looks up the MPLS label in its forwarding table and forwards the packet to the next hop.
5. This process repeats until the packet reaches its destination. At each hop, the router strips off the MPLS header and forwards the packet to the next hop.
MPLS is a protocol that can be used in both data and voice networks. In data networks, it can be used to improve performance or reduce congestion. In voice networks, it can be used to minimize delay and jitter.
How do Labels Forward in MPLS Network?
As mentioned above, in an MPLS network the data packets are forwarded with the help of short labels. There are three types of forwarding mechanisms used in MPLS:
Label Switch Path (LSP): In this type of forwarding mechanism, each LSR maintains a mapping between the label values and the next-hop LSR address. When a packet arrives at an LSR, the LSR looks up the label in its forwarding table and forwards the packet to the next-hop LSR specified by the table.
Label Switched Router (LSR): In this type of forwarding mechanism, each LSR maintains a routing table that is used to forward packets. When a packet arrives at an LSR, the LSR looks up the destination address in its routing table and forwards the packet to the next-hop LSR specified by the table.
Label Distribution Protocol (LDP): In this type of forwarding mechanism, each LSR maintains a label mapping database. When a packet arrives at an LSR, the LSR looks up the label in its mapping database and forwards the packet to the next-hop LSR specified by the database.
How Label Calculate in MPLS Network?
Each LSR in an MPLS network maintains a label forwarding table. This table is used to map labels to next-hop LSR addresses. When a packet arrives at an LSR, the LSR looks up the label in its forwarding table and forwards the packet to the next-hop LSR specified by the table.
The label forwarding table is populated using a label distribution protocol (LDP). LDP is a standard protocol that is used to distribute labels across an MPLS network.
What is MPLS VPN and What Types of MPLS VPN?
MPLS VPN is a type of VPN that uses MPLS labels to route traffic. There are two types of MPLS VPN:
Point-to-Point (P2P) VPN: In this type of VPN, each customer has a dedicated tunnel to the provider. The provider’s network is typically divided into multiple virtual routers, each of which is assigned a different MPLS label.
Multipoint VPN: In this type of VPN, each customer has a shared tunnel to the provider. The provider’s network is typically divided into multiple virtual switches, each of which is assigned a different MPLS label.
Importance of Cisco Express Forwarding CEF in MPLS Network?
Cisco Express Forwarding (CEF) is a Layer 3 switching technology that is used to forward packets through a network. CEF uses a forwarding table to map addresses to next-hop devices. When a packet arrives at a CEF-enabled device, the device looks up the destination address in its forwarding table and forwards the packet to the next-hop device specified by the table.
CEF is important in MPLS networks because it allows LSRs to quickly forward packets without having to perform a routing lookup at each hop. This reduces delay and improves performance.
What is Push and Pop in MPLS Network?
MPLS uses two operations to forward packets: push and pop.
Push: The push operation is used to add an MPLS label to a packet. When a packet arrives at an LSR, the LSR looks up the label in its forwarding table and pushes the label onto the packet. The packet is then forwarded to the next-hop LSR specified by the table.
Pop: The pop operation is used to remove an MPLS label from a packet. When a packet arrives at an LSR, the LSR looks up the label in its forwarding table and pops the label off of the packet. The packet is then forwarded to the next-hop LSR specified by the table.
What is MPLS L3 VPN?
MPLS L3 VPN is a type of VPN that uses MPLS labels to route traffic. An MPLS L3 VPN is typically composed of two types of devices:
- customer edge (CE) devices
- provider edge (PE) devices
CE devices are located at the customer’s site and are used to connect the customer’s network to the provider’s network.
PE devices are located in the provider’s network and are used to connect the customer’s CE devices to the provider’s backbone network.
MPLS L3 VPNs can be either point-to-point (P2P) or multipoint. In a P2P VPN, each customer has a dedicated tunnel to the provider. In a multipoint VPN, each customer has a shared tunnel to the provider.
Importance of VRF in MPLS Network
VRF is a technology that allows multiple virtual networks to coexist on a single physical infrastructure. VRF uses virtual routing and forwarding (VRF) tables to isolate traffic between different virtual networks.
VRF is important in MPLS networks because it allows LSRs to forward traffic for multiple VPNs using a single forwarding table. This reduces memory requirements and improves performance.