The MPLS WG Archive

["wu min" <made_in__china@hotmail.com>]

Hi,

In my opinion LFIB and LIB mean the same. LFIB/LIB contains information
as what Johannes listed. However I think I have encountered a reference 
which did not treat them as the same. In my opinion the reference refers LIB 
as a pool of labels that an LSR may use for label binding. The pool may 
contain several sets of valid label range.

I might be wrong here, but I think they are used inconsistently. Here are 
some references that you might want to see for yourself the usage of the 
terms LFIB and LIB:
1. http://students.cs.byu.edu/~cs460ta/cs560/slides/mpls-osbourne.ppt
2. http://flower.ce.cnu.ac.kr/~fog1/mns/mns1.0/MNS_v1.0_arch.pdf

Another term that is commonly used is FIB. IMHO, FIB is the normal L3 
routing table.

Other documents use ILM(Incoming Label Mapping), FTN(FEC-to-NHLFE), and 
NHLFE(Next Hop Label Forwarding Entry) to mean somewhat finer detail of 
LFIB/LIB.

Ignore this message if am incorrect at all.

-Tze Ven


>Roger Williams wrote:
>Johannes, it is my understanding that the LFIB contains what is
>actually being used to forward packets via label swapping, whereas the
>LIB contains all possible routes (generated by the underlying routing
>Link State Protocol) with labels already assigned (assuming frame mode
>MPLS). The LFIB is the outcome of an OS decision as to which route
>really is the Shortest Path. LFIB has only labels and interface
>information, with no IP information. The LIB has IP information, label
>and interface information, but no indication of which is the shortest
>path to the given destination.

>Any route in the LFIB will also be in the LIB, but not the other way
>around. The LFIB is a subset of the LIB, based on SPF algorithm
>calculation.

>Johannes wrote:
>I have found out that Label Forwarding Information Base (LFIB) is a
>subset of Label Information Base (LIB). I have not been able to find
>out exactly what information these two information bases contain.
>
>So far I found out LFIB contains:
>    -          Incoming Label
>    -          Outgoing Label
>    -          Next Hop
>    -          Outgoing Interface
>
>1. Is this correct and are there any other fields?
>
>I have not found any content specification for LIB.  RFC 3036, LDP
>Specification, explain that this information base contains, among
>other things, address prefix.
>
>2. What is address prefix?
>
>I assume this address is from the Forwarding Equivalence Class (FEC).
>3. Is this prefix also in the LFIB?
>4. What other parameters are in the LIB in addition to Incoming
>label, outgoing label and Interface?
>
>These should be explained in detail in RFC's but I've not found any
>information at IETF on this subject at all.

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• From: Roger Clark Williams <rogerw@nordlink.com>
• Date: Wed, 17 Apr 2002 10:18:34 -0400
• Resent-Date: Thu, 18 Apr 2002 07:49:50 -0400

Johannes, it is my understanding that the LFIB contains what is actually being used to forward packets via label swapping, whereas the LIB contains all possible routes (generated by the underlying routing Link State Protocol) with labels already assigned (assuming frame mode MPLS). The LFIB is the outcome of an OS decision as to which route really is the Shortest Path. LFIB has only labels and interface information, with no IP information. The LIB has IP information, label and interface information, but no indication of which is the shortest path to the given destination.

Any route in the LFIB will also be in the LIB, but not the other way around. The LFIB is a subset of the LIB, based on SPF algorithm calculation.

Roger Williams


At 03:02 PM 4/17/2002, you wrote:

Hi,
 
I have found out that Label Forwarding Information Base (LFIB) is a subset of Label Information Base (LIB). I have not been able to find out exactly what information these two information bases contain.
 
So far I found out LFIB contains:
    -          Incoming Label
    -          Outgoing Label
    -          Next Hop
    -          Outgoing Interface
 
1. Is this correct and are there any other fields?
 
I have not found any content specification for LIB.  RFC 3036, LDP Specification, explain that this information base contains, among other things, address prefix.
2. What is address prefix?
 
I assume this address is from the Forwarding Equivalence Class (FEC).
3. Is this prefix also in the LFIB?
4. What other parameters are in the LIB in addition to Incoming label, outgoing label and Interface?
 
These should be explained in detail in RFC's but I've not found any information at IETF on this subject at all.
 
 
 
Any answers will be appreciated. The questions have been enumerated.
 
Best regards,
 
Johannes Vea
Hallstein Lohne
Agder University College, Norway

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