Hi Jeffrey,
Ah ok, I see what you mean. The label column is basically based on this text in
section 3.1:
o The MPLS Label field is encoded as 3 octets, where the high-order
20 bits contain the label value. When sending, the label value
SHOULD be zero if recursive resolution based on overlay index is
used. If the received MPLS Label value is zero, the route MUST
contain an Overlay Index and the ingress NVE/PE MUST do recursive
resolution to find the egress NVE/PE. If the received Label value
is non-zero, the route will not be used for recursive resolution
unless a local policy says so.
We do care about the label value since, if it is zero we know for sure, there
must be an overlay index. In rows 1/2/3 we do not care, since the overlay index
indication is based on fields contained in the NLRI.
Thanks.
Jorge
On 10/17/17, 2:18 PM, "Jeffrey (Zhaohui) Zhang" <[email protected]> wrote:
Hi Jorge,
> >
+----------+----------+----------+------------+----------------+
> > | ESI | GW-IP | MAC* | Label | Overlay
Index |
> >
|--------------------------------------------------------------|
> > | Non-Zero | Zero | Zero | Don't Care | ESI
|
> > | Non-Zero | Zero | Non-Zero | Don't Care | ESI
|
> > | Zero | Non-Zero | Zero | Don't Care | GW-IP
|
> > | Zero | Zero | Non-Zero | Zero | MAC
|
> > | Zero | Zero | Non-Zero | Non-Zero | MAC or
None** |
> > | Zero | Zero | Zero | Non-Zero | None(IP
NVO)***|
> >
+----------+----------+----------+------------+----------------+
> >
> > The fifth row is like a variation of the fourth row; why isn't
there a
> > corresponding variation for each of the first three rows? The
following
> > paragraph mentioned earlier seems to apply to all situations.
> > [JORGE] in rows 4 and 5, the label value 0 or non-0 has a meaning.
In the
> first
> > three rows, the label doesn’t have any meaning.
>
> Can you elaborate on "the label does not have any meaning",
especially for
> row #2?
> [JORGE] since an overlay index is used, a recursive resolution is needed.
Hence
> the label is not used to forward packets. “Don’t Care” means a valid 0 or
non-
> zero label value should be ignored.
>
But Row 4/5 is the same - there is a MAC address as overlay index, so:
- either we "don’t care" the label for row 4/5 and just use overlay index,
or
- do the same with for rows 1/2/3 as with rows 4/5 and do label based
forwarding based on local policy
I'm just curious why there is a difference?
Thanks.
Jeffrey
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