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MPLS Label Distribution: LDP Part3

So far so good, we have finished two parts of LDP and in this post we are going to explore another function of the four major functions of LDP. After an LDP session is initialized, LDP peers start to exchange label mappings according to the pre-negotiated parameters. In this post I will assume that LDP is using the most common label distribution modes for as follows: MPLS Label Space: Per platform label space. MPLS label retention mode: Liberal label retention. MPLS Label distribution mode: unsolicited downstream. MPLS Label control mode: Independent label distribution.

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MPLS Label Distribution – LDP Part2

In my previous post I listed the main four functions of the label distribution protocol LDP and explained some concepts. In this post lets start dealing with the first two functions: Automatically discover LDP Peers in the same network segment. Establish and maintain LDP sessions with those peers. But I am not going to reinvent the wheel because I have already covered the two functions in older posts please have a look at them: LDP neighbor discovery, session establishment and maintenance. What is LDP extended discovery? We will soon do the next part, see you then.

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MPLS Label Distribution – LDP Part1

MPLS Label distribution protocol (LDP) as its name implies was defined to automatically create and maintain Label switched paths (LSP) in an MPLS network via label distribution. LDP specifications are defined in RFC 5036. In brief LDP assigns local label bindings to all IGP routes in the routing table and forms neighbor relationships with other LDP peers to exchange those local bindings. I will explain this further below. Label distribution Protocol (LDP) has four major functions as listed below: Automatically discover LDP Peers in the same network segment. Establish and maintain LDP sessions with those peers. Exchange and advertise label …

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The Role of BGP in MPLS networks

In almost every book you will read about MPLS, the author will state that one of the MPLS benefits is having a BGP free core network; sometimes they explain it sometimes not. However, to really understand this statement I encourage you to imagine removing MPLS from your core network and see what adjustments you need to do in order to get the transit traffic to its destination. Do thisĀ  just in your mind’s eye please If you are not willing to do this I will try in this post to bring the picture closer to you. Lets first examine the …

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MPLS Label Operations

In my previous post I explained what MPLS is and how it works from a high level perspective. In this post I will explain MPLS label operations and how labeled packets are processed in MPLS networks. When a labeled packet is received the label value at the top of the stack is examined to determine two things: The next hop and the exit interface to which the packet is to be forwarded. The operation to be performed by the LSR on the label stack before forwarding the packet. Listed below are the operations performed by the LSR on the MPLS …

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What is MPLS?

What is MPLS? MPLS stands for Multi-protocol Label Switching. MPLS is a packet forwarding technology that is capable of carrying any L3 protocol and here comes the word multi-protocol. MPLS is capable of tunneling L3 packets inside the MPLS network usingĀ  MPLS labels. The MPLS label is pushed into the packet between the layer two header and the layer three header of the packet at the ingress router and is used to switch the packets across the network to its destination. What is the MPLS Label and How is it used? The MPLS label is a fixed 4 byte identifier …

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