I’m currently doing a study about Traffic Engineering over MPLS
MPLS traffic engineering sets up LSP along links with available resources, thus ensuring that bandwidth is always available for a particular flow.The path computation is performed by the headend router, which is the source of the TE tunnel. The Headend routeur uses CSPF calculation which result with an ordered set of IP address that map to next-hop IP addresses of routers forming the LSP.
This path computation uses links related information resource availability including bandwidth per priority (0-7). These informations are flooded by IGP such as OSPF-TE and IS-IS-TE. Then, RSVP with TE extensions reserves appropriate resources on each LSR in the path defined by the headend router and assigns labels mapping to the TE tunnel LSP. Extensions added to RSVP (RSVP-TE) and link state protocols OSPF (OSPF-TE) and IS-IS (IS-IS-TE) enable the setting up of pre-emption. The available bandwidths on links are configured on priority basis. When setting up TE LSP path, if the requested bandwidth is in use by a lower priority session, the lower priority session can be pre-empted (RSVP send PATHERR and RESVERR messages to close the current connexion)
Here is, globally, what I understood about theoretical aspect.
What I would like to know, is, how pre-emption is applied in practice ?
How, starting from a query coming from a distant station, can it be established a new LSP which will preempt, if necessary, the LSP in place?
How is it possible to manage, dynamically, the creation of new LSP?
What I could see on the cisco routers configuration, specify command are used to create LSP (It is what I could call, static way, the domain administrator has in charge to write these command to configure his MPLS domain )
ip unnumbered Loopback0
tunnel destination 10.10.10.103
tunnel mode mpls traffic-eng
tunnel mpls traffic-eng autoroute announce
tunnel mpls traffic-eng priority 1 1
tunnel mpls traffic-eng path-option 1 dynamic
tunnel MPLS traffic-eng bandwidth 100
How the establishment of a new LSP, enable the dynamic reconfiguration of all the LSR present in the LSP?