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RSVP static LSP questions

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  • 1.  RSVP static LSP questions

    Posted 06-01-2020 10:39

    Hi everybody,

    Please consider the following questions:

    1) Let say we have a statically defined RSVP based  LSP with static BW 10M ( LSP is signalled for 10M) between two routers A and B.
    What is the default behavior if A starts sending 11M on that LSP? Is the traffic policed or allowed to pass through LSP?

    2) MXA-f1-10M-f1-MX2
           f2-5M--f3
    SPF path is top path i.e f1 between MX1 and MX2
    Assume we have LSP1A->B with allocated BW 9M having set up priority 7 hold priority 7
    Let say we want to establish another RVSP based  LSP2A->B with BW 9M , having set up prioirty 0 hold priority 0
    What will happen next ?
    Will MX1 move LSP1 to f2 and place LSP2 on f1 or will it put LSP2 on f2 and leave LSP1 on f1?

    3) Let say we have a static LSP as shown below
    set protocols mpls label-switched-path LSP1 to 2.2.2.2

    Above no BW is defined for LSP, what BW will RSVP signal as none is defined? if RSVP signales LSP without BW contraint, then what is the max BW this LSP can carry?

    Thanks and have a good day!!



  • 2.  RE: RSVP static LSP questions
    Best Answer

    Posted 06-01-2020 20:01

    Hello

    First things first - JUNOS supports "static LSP" where no signalling is used AT ALL , they are defined under [edit protocols mpls static-label-switched-path ]

    https://www.juniper.net/documentation/en_US/junos/topics/topic-map/primary-secondary-static-lsp-configuration.html

    _AND_
    JUNOS also supports RSVP-signalled LSP which are defined under  [edit protocols mpls label-switched-path ] AND RSVP protocol needs to be enabled under [protocols rsvp interface BLAH]

    My guess is that You are interested in RSVP-signalled LSPs, not static ones.

    Hence I will continue with RSVP-signalled LSPs only.

    I also strongly recommend to read JNCIE Study Guide by Harry Reynolds chapter 2 :  https://forums.juniper.net/jnet/attachments/jnet/JNCIPJNCIE/23/1/JNCIE_studyguide.pdf

     

     


    @sarahr202 wrote:

    Hi everybody,

    Please consider the following questions:

    1) Let say we have a statically defined RSVP based  LSP with static BW 10M ( LSP is signalled for 10M) between two routers A and B.
    What is the default behavior if A starts sending 11M on that LSP? Is the traffic policed or allowed to pass through LSP?

     

     

    By default, all traffic mapped to this LSP passes, if You want this traffic to be policed, You need to enable LSP auto-policing

    https://www.juniper.net/documentation/en_US/junos/topics/reference/configuration-statement/auto-policing-edit-protocols-mpls.html

     

     


    @sarahr202 wrote:

     

    2) MXA-f1-10M-f1-MX2
           f2-5M--f3
    SPF path is top path i.e f1 between MX1 and MX2
    Assume we have LSP1A->B with allocated BW 9M having set up priority 7 hold priority 7
    Let say we want to establish another RVSP based  LSP2A->B with BW 9M , having set up prioirty 0 hold priority 0
    What will happen next ?
    Will MX1 move LSP1 to f2 and place LSP2 on f1 or will it put LSP2 on f2 and leave LSP1 on f1?

     

     

    f2-5M-f3 BW is not enough to accomodate LSP1 or -2 with 9Mbps TSpec, so by default the LSP1 will be preempted, and then LSP1 will be always Down because it won't find 9Mbps of free BW.

    If You want both LSPs to establish, use "adaptive" knob so Your f1-10M-f1 link BW will be shared https://www.juniper.net/documentation/en_US/junos/topics/usage-guidelines/mpls-configuring-adaptive-lsps.html

     

     


    @sarahr202 wrote:

     

    3) Let say we have a static LSP as shown below
    set protocols mpls label-switched-path LSP1 to 2.2.2.2

    Above no BW is defined for LSP, what BW will RSVP signal as none is defined? if RSVP signales LSP without BW contraint, then what is the max BW this LSP can carry?


    LSP1 will be signalled with Tspec 0 bps, and can carry as much traffic as there is free BW along its path, up to the smallest link' available BW.

     

    HTH

    Thx

    Alex