The MPLS WG Archive

["Subodh Mathur" <subodh@dtix.com>]

By using loose hop problem mentioned below can be solved.
Suppose second LSP is to terminate at LER10 which is topologically adjacent
to LSR6.

        LER2----->LSR5----->LSR7----->LSR4----->LSR6----->LER10

So if LER2 construct a ER TLV with  ER-Hops <LSR5, LSR7, LER10> where LER10
is a loose ER-Hop. LSR7 will determine using some routing algo. that LSR4 is
the next hop. So it will modify the ER TLV as <LSR4, LER10>.  Now LSR4 can
use its knowledge of existing LSP ID for tunneling and ER TLV will be
<LSPID, LER10>.
Subodh

> One more issue that crops up at this point is that how is this type of LSP
> to be setup. The initial scenario that we discussed was
>
>                 LER1 ------> LSR2-------->LSR3------>LSR4
>
>                 LER2-------->LSR5
>
> Now suppose the scenario were like
>
>                 LER1 ------> LSR2-------->LSR3------>LSR4------>LSR6
>
>                 LER2-------->LSR5------->LSR7
>
> and LSR7 was supposed to connect to LSR4. How is the new LSP to be setup?
> The  global (or, supra-local) entity will inform only LER2 which will be
> sending message to LSR5 which would in turn send the request to LSR7. Is
> there any standard draft on how this is to be handled?
>
> Santosh Gupta
>