[j-nsp] Confusing terminology for LSPs in Junos

[Ben Dale]

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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