[j-nsp] Confusing terminology for LSPs in Junos

[John Neiberger]

Got it. I tend to always think of commands as being from the perspective of
the router. In this case, the perspective is the LSP itself, which has an
ingress side and an egress side. That makes perfect sense. I knew they were
unidirectional but I still thought from a router's perspective, the ingress
LSP would be the one that had traffic arriving, when it is actually the
egress LSP because that is where the traffic leaves the LSP.

Thanks!
John


On Sat, May 10, 2014 at 5:11 AM, Ben Dale <bdale at comlinx.com.au> wrote:

>
> On 10 May 2014, at 2:28 pm, Tyler Christiansen <tyler.christiansen at adap.tv>
> wrote:
>
> > Look at it from the perspective of where the traffic is entering the LSP,
> > not the perspective of the router.
> >
> > When the traffic is encapsulated (enters the LSP), that's the ingress
> LSP.
> > When a packet leaves an LSP, that is the egress LSP.  The fact that it
> > enters or exits the router (and where it does so) is inconsequential in
> the
> > context of discussing the direction of an LSP.
>
> Following on from Tyler's points, think also on the fact that an LSP is
> uni-directional - ingress for the head-end where the LSP is signalled from
> and where traffic enters and egress for the termination point where traffic
> exits.
>
> > On Fri, May 9, 2014 at 8:23 PM, John Neiberger <jneiberger at gmail.com>
> wrote:
> >
> >> I just took a Juniper MPLS and VPNs course and I have a question about
> the
> >> ingress and egress types of LSPs. The terminology makes zero sense to
> me.
> >> The LSP that is used to send traffic is called the ingress LSP, and the
> LSP
> >> used to receive traffic is an egress LSP. How in the heck does that make
> >> any sense? It seems exactly backwards. From the perspective of the
> router,
> >> why would egress traffic leave on the ingress LSP and vice versa?
> >>
> >> This seems really odd, but I presume there must be a really good reason
> for
> >> it.
> >>
> >> John
> >> _______________________________________________
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