The MPLS-OPS Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] Re: Congested TCP/LDP - How to confirm that the labelactually made it to the (targeted) peer!
Thanks Wanglei for your response. It was my bad. Actually, I put out the question incorrectly. My doubt is more relevant to the L2VPN (maritini). For an L2VPN, I am dealing with a requirement that a VC between two LERs should be bi-directional. That is, data-flow from A-to-B should be activated only iff B-to-A is also activated. So my first question is - is this a legitimate and reasonable requirement? I think it isn't - given that VC from A-to-B can come up as soon as label advertised by B reaches (and is installed) by A. A should not have to wait for it's label to reach B. Now my earlier question - if it is a reasonable requirement. how one can built such a system? Properietary solutions usin vendor specific pdu's won't survive the inter-op. regards - manish wanglei wrote: >in LDP specs, there is no confirm when LSR-B receives label mapping from LSR-A. >in fact ,if the A hasn't receive the label mapping from B, the packet from A won't >be sent to B with label, it is just sent out as ip packet. >so ,when A has sent the label mapping , it can't indicate that the LSP is established. >you can see one of the L2VPN protocols (martini), it explains the problem more clearly. > > >----- Original Message ----- >From: "Manish Gupta" <manish@xebeo.com> >To: <mpls-ops@mplsrc.com> >Sent: Thursday, February 20, 2003 4:46 AM >Subject: [MPLS-OPS]: Congested TCP/LDP - How to confirm that the label actually made it to the (targeted) peer! > > > > >>Hello >> >> I have one doubt which I am not being able to resolve by reading >> LDP specs. Hoping that somebody on the list will be able to help >> me out. >> >> Here is the scenario: >> >> [LSR-A] ----- <targeted ldp session> ----- [LSR-B] >> >> note.1: LSR-A and LSR-B are *NOT* connected directly. >> >> Time-1: <A> and <B> establish a targeted ldp session. >> >> Time-2: <A> sends a label map to <B>. >> >> Time-3: <B> receives label map from <A> >> >> In the above scenario, <A> has no means to detect when did >> <B> actually received its label. Once <A> puts the packet on >> the wire, it assumes (thanks to reliable TCP) that label will >> reach <B>. The difference between Time-3 and Time-2 >> could be significant if network connecting <A> and <B> is >> congested. The packet may end up sitting in TCP queues >> for sometime. >> >> If I am not mistaken, <A> has no means to detect this time >> difference and may (incorrectly) start sending out labeled >> packets to <B> and if data packets reach <B> before label >> could be installed, they will get dropped (data packet >> does not have to take the same path as the label pdu). >> >> Can anybody explain how one can handle this? Build some >> sort of end-to-end LDP level reliability. >> >> thanks >> manish >> >>------- >>The MPLS-OPS Mailing List >>Subscribe/Unsubscribe: http://www.mplsrc.com/mplsops.shtml >>Archive: http://www.mplsrc.com/mpls-ops_archive.shtml >> >> >> ------- The MPLS-OPS Mailing List Subscribe/Unsubscribe: http://www.mplsrc.com/mplsops.shtml Archive: http://www.mplsrc.com/mpls-ops_archive.shtml
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