What is PLR, Point of Local Repair in MPLS Traffic Engineering ?
MPLS Traffic Engineering Fast Reroute Link Protection – I will explain it in plain English and the most important point of MPLS TE FRR Link Protection among other Fast Reroute mechanisms.
MPLS Traffic Engineering is a mechanism that provides cost savings in an MPLS networks.
How cost saving can be achieved ? How traffic is steered to the paths which wouldn’t be used in normal circumstances ? I will explain in this post.
If I input MPLS traffic engineering on any search engines, I will find about 100 articles on the internet providing the same explanations about MPLS traffic engineering.
But unfortunately, nobody ask these questions: do I really need it? What are the reasons behind the implementation of MPLS Traffic Engineering?
Would it worth the time and energy to deploy and learn such a complex technology if there are many easier, resource-friendly alternatives.
In this article, I will explain all the answers to these questions. Undoubtedly, MPLS traffic engineering has many used cases and it helps to solve numerous problems in an MPLS enabled networks.
You need OSPF or IS-IS to distribute link information such as reserved, unreserved and used bandwidth, metric, link colouring information.These informations are used by CSPT ( Constraint based shortest path first ) algorithm.
For those who are familiar with MPLS-Traffic Engineering, path is calculated either at each and every device or with the offline computation tools such as NMS from the central place.
For the distributed computation, CSPF which is one of the flavour of Shortest Path First (SPF) algorithm is used.
CSPF computes a dynamic unidirectional MPLS TE LSP ( Label Switch Path ) by reaching the Traffic Engineering Database (TED).
TED database has different attributes than regular link state database which is created such as reserved , used , unreserved bandwidth on the interfaces, link colouring attributes and so on.Link colouring information is used to avoid SRLG ( Shared Risk Link Group ) path at the transport network.
These information can only be provided by the link state protocols. Thus if you want to calculate the MPLS TE LSP without helping the NMS ( Network Management System ) but on each and every LSR as distributed, you need to use link state routing protocols which are OSPF and IS-IS currently.