Re: RSVP and LDP

The order of labels will be VPN label exchanged and the RSVP TE label man.

PE1-------------P3------------------P4----------------P5--------------P6-----
------------P7------------------------PE4

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|

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|

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PE2
PE3

So in this scenario PE1 ,PE2 to P connections run LDP. From P3 to P7
there will be RSVP....From P3 to P7 there will be Targeted LDP established
to exchange the label for corresponding PE . lets see the thought process

Here P7 will form a targeted LDP with P3 and exchange labels for PE3 and
PE1 respectively.

Now P3 will update PE1 about PE3 via its local label.. and now LSP from PE
1 to PE3 will be the LDP label given by P3 and when it reaches P3, it
uses the Targeted LDP label recevied from P7 and to reach P7 it uses RSVP
label given by P7 when forming the TE tunnel.

So P4, P5 and P6 have no idea about PE1 and PE3

So Over RSVP there will be LDP and this way it works

LDP over RSVP solves the problem of creating many LSPs . For example u have
to create as many LSPs as number of PE's
Lets assume ur POP has 5 PE routers connected to 2 P routers connected to
each other in each site. Think there are 7 sites. So totally 35 PE routers
and 14 P .. So for each PE to PE there will be LSPs created. so in this
case 35 PE's so 35*34 LSPs has to be formed

When u use LDP over RSVP, there will be only 14*13 LSPs created

So it basically avoids number of LSPs

2012/2/2 Mustafa Yadav <mustafa.yadav_at_gmail.com>

> This makes sense and. I have found ldp over rsvp is used and there are
> 3 labels are used.vpn rsvp and ldp label
>
> 2012/2/2, CCIE KID <eliteccie_at_gmail.com>:
> > Good explanation Hemanth
> >
> > TE is used to engineer the traffic as u want to go through with the
> > prioritized traffic in need of B.W. There many be different LSP's and
> you
> > assign different treatment for each LSP.
> > And also u can do LDP over RSVP where u can do RSVP TE Tunnel from one P
> to
> > another P . So from PE to P u run LDP and have a targeted LDP over ur
> RSVP
> > So its basically hierarchical LDP over ur RSVP .
> >
> > On Thu, Feb 2, 2012 at 6:13 PM, HEMANTH RAJ <hemanthrj_at_gmail.com> wrote:
> >
> >> Hi Mustafa
> >>
> >> LDP has been designed for distributing labels exclusively, But RSVP has
> >> been a Host based protocol to inform the transit routers that to reserve
> >> the bandwidth what the application needs.
> >> So here in MPLS TE , RSVP is used as a signalling protocol to establish
> a
> >> BANDWIDTH DEFINED LSP from head end router to your Tail End Router
> >>
> >> In ur normal LDP , For each prefix u build a particular LSP . These
> >> prefixes are distributed by ur CORE IGP. SO basically ur LDP is relying
> on
> >> ur IGP info for setting up a LSP for that prefix
> >>
> >> But in MPLS TE, RSVP will build a LSP with the Tail End Router with some
> >> constraints. So basically it is a Tunnel where ur Head End Router is
> >> trying
> >> to form with the Tail End and to switch packets on the Tunnel. It is a
> >> unidirectional Tunnel.
> >>
> >> TE also uses ur CORE IGP to check whether the requirements to form a
> >> tunnel are met. For example , If the TE Tunnel requires 500Kb of
> bandwidth
> >> ie ur Head End's routers requirement is 500Kbs of B.W end to end (
> Assume
> >> that there are some users sitting behind Head End Router which requires
> a
> >> 500kb feed from the server which is present behind ur Tail End Router )
> So
> >> now ur Head End has to know the end to end B.W capacity of each transit
> >> router . This information is fed by our CORE IGP which can be ISIS or
> OSPF
> >> . ( These r the two protocol in use currently which has the capability
> to
> >> carry MPLS TE extended attributes . OSPF uses Opaque LSA and ISIS uses
> >> extended TLVS for it )
> >>
> >> So TE Tunnel will be up only when it is met with these requirements and
> >> after that it signals the RSVP Path and Tail End will send Reserve
> >> Messages
> >> to assign Labels ..
> >> This is also same as ur LDP where ur Downstream router starts assigning
> >> labels to the prefixes.
> >>
> >> So basically LDP is a prefix driven label assignment protocol but RSVP
> is
> >> all about how ur Head End wants the Constraint driven LSP with ur Tail
> >> End
> >> router and ( so u must know ur network and u know there is greedy hosts
> >> which wants a feed and u configure the TE Tunnel accordingly )
> >>
> >> Without LDP also, RSVP will work .For RSVP u just need ur CORE IGP to be
> >> converged and has the capabilities to carry TE extended information ( So
> >> no
> >> RIP and EIGRP as of now ) RSVP Head End just sends Path message to ur
> >> Tail
> >> End router to signal each and every transit router that this is the
> >> requirement
> >>
> >> Do not confuse between LDP and RSVP. LDP is always Prefix Driven From
> IGP
> >> .. RSVP is basically manually configured Constraint Driven LSP ( knowing
> >> ur
> >> network end to end )
> >>
> >> Hope this helps :)
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >>
> >> On Thu, Feb 2, 2012 at 5:43 PM, GAURAV MADAN <gauravmadan1177_at_gmail.com
> >> >wrote:
> >>
> >> > I think things are being mixed up here .
> >> >
> >> > When RSVP is used with TE .. RSVP will do the label distribution .
> >> > Hence role of LDP as a protocol for label distibution is eliminated as
> >> you
> >> > are doing same thing using RSVP .
> >> >
> >> > And also ; i believe that in MPLS L3 VPN scenario as well ; running
> only
> >> > RSVP and no LDP anywhere in core can achieve your goal .
> >> >
> >> > Regards
> >> > Gaurav Madan
> >> > CCIE
> >> >
> >> > On Thu, Feb 2, 2012 at 5:14 PM, Mustafa Yadav <
> mustafa.yadav_at_gmail.com
> >> > >wrote:
> >> >
> >> > > so when ldp is going down all te tunnles are going to be down?
> >> > >
> >> > > but in one of my case ldp goes down but te tunnels did not.
> >> > >
> >> > > Also I seee ldp neigbor is up for 4 hours but mpls te tunnel up for
> 8
> >> > > hours.and 4 hours ago ldp went down.
> >> > >
> >> > > On Thu, Feb 2, 2012 at 1:18 PM, sundeep sadhwani <
> >> > > sundeep.sadhwani_at_gmail.com
> >> > > > wrote:
> >> > >
> >> > > > Hi Mustafa,
> >> > > >
> >> > > > RSVP is used for reservation of bandwidth in TE environment( i am
> >> > giving
> >> > > u
> >> > > > a very high level view). However plain MPLS-TE is not used in
> >> > production
> >> > > > scenario as SPs have MPLS-VPN as well. for that purpose we require
> >> LDP
> >> > as
> >> > > > well to distribute IGP labels that will be required for PE to PE
> >> > > > communication in case of MPLS-VPN.
> >> > > >
> >> > > > Regards
> >> > > > Sundeep
> >> > > >
> >> > > > On Thu, Feb 2, 2012 at 4:41 PM, Mustafa Yadav <
> >> mustafa.yadav_at_gmail.com
> >> > > >wrote:
> >> > > >
> >> > > >> HD0,
> >> > > >>
> >> > > >>
> >> > > >> In a cisco network I have seen mpls traffic engineneering tunnels
> >> are
> >> > > >> being
> >> > > >> used .So as far as I know rsvp must be configured .But I alos see
> >> that
> >> > > ldp
> >> > > >> is configured in all boxes.why is that?Is not rsvp enough for
> >> > > distrbuting
> >> > > >> labels?
> >> > > >>
> >> > > >>
> >> > > >> Blogs and organic groups at http://www.ccie.net
> >> > > >>
> >> > > >>
> >> >
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> >> >
> >> >
> >> >
> >> >
> >> >
> >> >
> >> >
> >>
> >>
> >> --
> >> Problems arise because we talk,problems are not solved because we don't
> >> talk So good or bad talk to your affectionate one's freely.
> >>
> >> Yours Friendly,
> >> H P HEMANTH RAJ
> >> CCIE#28593 (R&S)
> >> Cisco Systems
> >>
> >>
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> >>
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> >
> >
> > --
> > With Warmest Regards,
> >
> > CCIE KID
> > CCIE#29992 (Security)
> >
>
> --
> Mobil cihaz}mdan gvnderildi
>

--
With Warmest Regards,
CCIE KID
CCIE#29992 (Security)
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