Downstream on demand - MPLS device do not signal a FEC to label binding unless it is requested by an upstream device
Downstream unsolicited - MPLS device will signal FEC to label bindings without waiting for a request from upstream
Liberal label retention mode - maintains the binding between a label and a FEC which are received from LSRs which are not its next hop for that FEC eg:- LDP
Conservative label retention mode - discards such bindings
Ordered control - LSR will not signal FEC to label binding to its peer unless it is the egress of the LSP or until it has received a label from the peer
Independent control - LSR will signal FEC to label bindings independent of the other routers
- Downstream on demand, ordered control with RSVP-TE
- Downstream unsolicited, independent control or ordered control with LDP(ordered control is default)
BGP accepts only downstream unsolicited, ordered control.
How does a router distinguish between a normal IP packet and an MPLS packet?
By using the ethertype/length field of the ethernet header.(13 and 14 octects after preamble) A value of 0x0800 indicates IP packet whereas 0x8847 indicated MPLS unicast packet.
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