3com S7906E 설치 설명서

 

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with MPLS echo replies. If the ping initiator receives the replies, the LSP is considered perfect for 
forwarding data. 

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MPLS LSP traceroute is a tool for locating LSP errors. By sending MPLS echo requests to the 
control plane of each transit LSR, it can determine whether the LSR is really a transit node on the 
LSP. 

 

The destination address in the IP header of an MPLS echo request is set to an address on 127.0.0.0/8 
(a loopback address of the LSR) and the TTL is set to 1, so as to prevent further forwarding of the 
request when the request reaches the egress. 

 

The LDP protocol dictates the messages to be used in label distribution and the related processes. 

Using LDP, LSRs can map network layer routing information to data link layer switching paths directly 
and further establish LSPs. LSPs can be established between both neighboring LSRs and LSRs that 
are not directly connected, making label switching possible at all transit nodes on the network. 

 

For detailed description about LDP, refer to RFC 3036 “LDP Specification”. 

 

Two LSRs with an LDP session established between them and using LDP to exchange label bindings 
are called LDP peers, each of which obtains the label bindings of its peer over the LDP session between 
them.  

LDP sessions are used to exchange messages for label binding and releasing.  

LDP sessions come in two categories: 

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Local LDP session: Established between two directly connected LSRs. 

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Remote LDP session: Established between two indirectly connected LSRs. 

There are four types of LDP messages: 

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Discovery message: Used to declare and maintain the presence of LSRs on a network. 

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Session message: Used to establish, maintain, and terminate sessions between LDP peers.