MPLS
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... Frame Relay switching, along with other
labels, if the packet is multiply labeled, are carried in the generic
MPLS encapsulation defined in [STACK].
...
... label switching based traffic. The DLCIs would be used as MPLS
Labels and the Frame Relay switches would become Frame Relay ...
... switches would become Frame Relay Label
Switching Routers, while the MPLS traffic would be encapsulated
...
... Frame Relay, ATM, Generic) of a packet that determines the
packet's MPLS forwarding, or the network layer encapsulation ...
...
The Input TTL is the MPLS TTL of the top of the stack when a
labeled packet is received on an LSR ...
...
The Output TTL is the MPLS TTL of the top of the stack when a
labeled packet is transmitted on an LSR ...
... n | . |
/ . /
/ MPLS packet /
| . |
+-----------------------+-----------------------+
...
... With the exception of this configured value, the DLCI values used for
MPLS in the two directions of the link may be treated as belonging to
two independent spaces, i.e., VCs ...
... encoding when transmitting a packet P
to LSR3. In general, the MPLS architecture supports LSPs with
different label stack encodings ...
... LSRs, and other LSRs, which operate
using other MPLS encapsulations, such as the Generic (MPLS shim
...
... interfaces as well as MPLS Generic
("MPLS Shim") interfaces. This is one example of an LSR with
...
... Frame Relay encoded label on an incoming
interface and replace it with a label encoded into a Generic MPLS
(MPLS shim) header ...
... interface and replace it with a label encoded into a Generic MPLS
(MPLS shim) header on the outgoing interface.
...
...
The initial value of the MPLS TTL is loaded into a newly pushed label
stack entry from the previous TTL value ...
... FR-LSR switching same level labeled packets does not decrement the
MPLS TTL. A sequence of such FR-LSR ...
... When an ingress FR-LSR determines upon decrementing the MPLS TTL that
a particular packet's TTL ...
... Frame Relay |
+----------------+-----------------+-----------------+-----------------+
| 1 | any | Generic MPLS | Generic MPLS |
+----------------+-----------------+-----------------+-----------------+
...
... +----------------+-----------------+-----------------+-----------------+
| 1 | any | Generic MPLS | Generic MPLS |
+----------------+-----------------+-----------------+-----------------+
| number of hops | | Generic MPLS ...
... MPLS |
+----------------+-----------------+-----------------+-----------------+
| number of hops | | Generic MPLS | |
| of | any | or | Frame Relay |
...
... Frame Relay |
+----------------+-----------------+-----------------+-----------------+
| | | Generic MPLS | |
| 1 | any | or | Frame Relay |
...
... layer)| |
+----------------+-----------------+-----------------+-----------------+
| number of hops | | Generic MPLS | |
| of | Frame Relay | or | any |
...
... MPLS, and "F" for Frame Relay
MPLS, referring to an LSR interface with the abbreviation "i" if the
...
... input or output encapsulation is IP and no MPLS encapsulation, "g"
when the input or output MPLS ...
... MPLS encapsulation, "g"
when the input or output MPLS encapsulation is Generic MPLS, "f" when
...
... when the input or output MPLS encapsulation is Generic MPLS, "f" when
it is Frame Relay, "a" when it is ATM ...
... LSP; it calculates: mpls_ttl=n-1
"gGf" is "egress LSR" from Generic MPLS segment, and
"ingress LSR ...
... segment and calculates: mpls_ttl=n-9
"gGf" is "egress LSR" from Generic MPLS segment, and
"ingress LSR ...
... segment, and
ingress LSR" in Generic MPLS segment and calculates: mpls_ttl=n-14
"gIi" is "egress LSR ...
... layer forwarding operations with the exception that
the outgoing encapsulation will include an MPLS label stack [STACK]
with at least one entry. The frame relay ...
...
For unicast packets, the MPLS TTL SHOULD be decremented with the
number of hops of the Frame Relay ...
... DLCI. The Frame Relay
frame carrying the MPLS encapsulated packet is forwarded onto the
Frame Relay ...
... In a FR-LSR, the current (top) MPLS label is carried in the DLCI
field of the Frame Relay data link layer ...
... If the label popped is not the last label, the previous top level
MPLS TTL is propagated to the new top label stack entry.
...
... segment is not the end of
the LSP, the MPLS packet will be processed for forwarding onto the
next segment of the LSP ...
... ARCH]. The output label is set to
the value from the NHLFE, and the MPLS TTL is decremented by the
appropriate value depending the type of the output interface ...
... appropriate value depending the type of the output interface and the
type of transmit operation (see section 6.3). Further, the MPLS
packet is forwarded according to the MPLS specifications for the
particular link ...
... interface and the
type of transmit operation (see section 6.3). Further, the MPLS
packet is forwarded according to the MPLS specifications for the
particular link of the next segment ...
... Control and state information for the circuits based on MPLS MAY be
communicated through LDP.
...
... PVCs and/or
SVCs when both are running on the same interface as MPLS, as
discussed in the next section.
...
... TTL calculation. Once this is done, the LSR may
use MPLS forwarding to transmit packets in that FEC.
...
...
The MPLS protocol has no mechanisms of its own to protect against
misdirection of packets or the impersonation of an LSR ...
... Rosen, E., Rehter, Y., Tappan, D., Farinacci, D., Fedorkow, G., Li, T. and A. Conta, "MPLS Label Stack Encoding", RFC 3032prop, January 2001. ...