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 label actually made it to the (targeted) peer!
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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