Re: RSVP and LDP

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

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