MPLS Guide MPLS and RSVP-TE
3HE 18686 AAAB TQZZA © 2022 Nokia.
Use subject to Terms available at: www.nokia.com
25
• A value of 1 represents the router alert label. This label value is legal anywhere
in the label stack except at the bottom. When a received packet contains this
label value at the top of the label stack, it is delivered to a local software module
for processing. The actual packet forwarding is determined by the label beneath
it in the stack. However, if the packet is further forwarded, the router alert label
should be pushed back onto the label stack before forwarding. The use of this
label is analogous to the use of the router alert option in IP packets. Since this
label cannot be at the bottom of the stack, it is not associated with a particular
network layer protocol.
• A value of 3 represents the Implicit NULL label. An LER advertises this when it
is requesting penultimate hop popping (PHP) and expecting unlabeled packets.
The label value 3 should never appear in the label stack.
• A value of 7 represents the entropy label indicator (ELI). The ELI is a special-
purpose MPLS label that indicates that the entropy label (EL) follows it in the
stack.
• Values 4 through 6 and 8 through 15 are reserved for future use.
Table 3 lists the label ranges available for use by ingress labels (pop labels).
Note:
1. In addition, users can define part of the dynamic label range from 18 432 to 131 071 to be the
range of labels for the segment routing global block (SRGB).
Table 3 Ingress Label Values (Pop Labels)
Label Values Description
16 through 31 Reserved for future use
32 through 1023 Available for static outer LSP tunnel label assignment
1024 through 2047 Reserved for future use
2048 through 18 431
1
Statically assigned for services (inner pseudowire label)
32 768 through 131 071 Dynamically assigned for both MPLS and services
131 072 through 1 048 575 Reserved for future use
To Next Page
Loading...
Need help?
General
