Part 3: MPLS Forwarding Operations With Labels

MPLS Forwarding Operations With Labels

In our earlier articles, we talked about MPLS labels, Special Labels and now we will go through the MPLS Forwarding Operations using labels in the core.

Labels are being used to establish end to end connectivity and for that purpose we use three kind of operations with Labels and these are 

  • Label imposition
  • Label Swapping
  • Label disposition
Fig 1.1- MPLS Labels

Label imposition : As name suggested, Label imposition where we add the label to the MPLS packet and do the push operation with the MPLS network. The label us imposed by ingress PE router and it classify. As we enabled FEC (Forwarding Equivalence Class), the packet is pushed to the next hop with the label assigned by PE.

Note ⭐ : Label imposition always called as Push operation in MPLS network.

Label Swapping : Now the packet is in the core, so all routers are P routers. So they checked the label on that packet and swap the label with the new one. Once label swapped the packet with the new label pushed to next hop ( there might be multiple P routers, so every time packet reached to new Hop, the label will be swapped with the new one).

Label disposition : Once the packet reached to the egress PE router, the label is removed from the packet and forward the original packet to the destination CE router.

Note ⭐ : Label disposition always called as Pop operation in MPLS network.

Note ⭐ : In this article, we only talked about the Labels, MPLS forwarding operation is depending upon LDP/RSVP protocols as well.

No comments