DISCUSIÓN DE RESULTADOS

6.6.1 Overview

This section will describe the use of Multi-Protocol Label Switching (MPLS) for forwarding traffic within the VN2 IP Core network.

P P

ASBR

PE Single Hop RSVP RSVP Full

Mesh Between P routers

PE

POP A P P POP B

RSVP Signaled LSP LDP over RSVP

Figure 10: VN2 MPLS Topology 6.6.2 Usage

MPLS will be used in two fundamental ways in the VN2 network. The first is as the baseline forwarding scheme across the WAN portion of the network, providing traffic engineering and fault protection. And second tier of MPLS is used as a unified means of connectivity between edge routers, enabling end-user services like Layer3 VPNs, VPLS, and Pseudowires.

Two sets of protocols, participants, and topologies will be used for each, as follows:

Backbone MPLS:

• RSVP and LDP protocols

• Full mesh RSVP LSPs between P routers

• LDP will be enabled for full mesh topology to be dynamically created by default

• Statically configured dual mesh topology (A + B planes)

• Traffic Engineering (TE) capabilities

• Enhanced fault protection capabilities

Edge MPLS:

• LDP and RSVP protocols

• Single hop RSVP LSPs between P router and PE or ASBR

• T-LDP sessions between PEs and ASBRs will be tunnelled over RSVP tunnels (LDPoverRSVP)

• LDP will be enabled for full mesh topology to be dynamically created by default

• Follows IGP to determine paths, dependent for re-convergence

• Graceful restart and Non stop routing enabled for LDP

6.6.3 Backbone MPLS

The backbone MPLS scheme based on the Resource Reservation Protocol (RSVP) protocol provides a highly configurable framework for forwarding traffic across the core of the network. As RSVP LSPs must be explicitly configured at the origin for each source-destination pair, its use of full mesh is generally confined to the network core, in order to limit the size of the N squared full mesh of LSPs among participating PE routers. In the VN2 network, the full mesh RSVP LSPs will be limited to the P routers.

6.6.4 RSVP Signalled LSP Topology

The following grids give a complete list of the unidirectional RSVP signaled LSPs to be configured among the P routers. Check marks indicate an LSP which corresponds to a direct physical link. Check-plus indicates an LSP with an intermediate hop.

Plane A From:

To:

P1 - HPY P1 - HNI P1 - DNG P1 - HCM P1 - CTO

P1 - HPY 9 9 9+ 9+

P1 - HNI 9 9 9 9+

P1 - DNG 9 9 9 9

P1 - HCM 9+ 9 9 9

P1 - CTO 9+ 9+ 9 9

Plane B From:

To:

P2 - HPY P2 - HNI P2 - DNG P2 - HCM P2 - CTO

P2 - HPY 9 9 9+ 9+

P2 - HNI 9 9 9 9+

P2 - DNG 9 9 9 9

P2 - HCM 9+ 9 9 9

P2 - CTO 9+ 9+ 9 9

Interlinks

From: To:

P1 - HPY P2 - HPY

P1 - HNI P2 - HNI

P1 - DNG P2 - DNG

P1 - HCM P2 - HCM

P1 - CTO P2 - CTO

6.6.5 Traffic Engineering

RSVP provides a number of features for fine grained control over the path selection for each LSP, collectively providing the Traffic Engineering (TE) capabilities. Those

parameters include a subscribed bandwidth per LSP, admin groups (or „colors‟) per link for inclusion or exclusion, a link metric scheme for TE, and the hop count. Also, RSVP paths can be explicitly defined on a per-hop basis, or allowed to follow the same IGP metric based path selection.

As the traffic levels are expected to be low on the VN2 network on day one, but are

otherwise unknown, it is proposed to use a course bandwidth allocation scheme, well below the actual available link bandwidth. This scheme may be used for

future true bandwidth subscription based TE, or as a means to load share paths across future parallel links.

Otherwise, the largely single-hop LSP topology, and the implied primary/backup paths given by the physical circuit topology, largely negate the need for other types of TE configuration. Only the LSP marked with a check-plus in the above grid

have any intermediate hop which might be subject to a policy based path decision, and these would be expected to be among the lowest bandwidth consumption

paths. As such, no other TE configuration is recommended, and the use of the IGP cost scheme to determine LSP paths should be sufficient.

6.6.6 Edge MPLS

The edge MPLS scheme leverages the multiprotocol capabilities of MPLS to support converged service offerings. Single hop RSVP LSPs will be used to connect the PE and P routers. The RSVP full mesh is only within the P routers. Source PE routers will use LDP over RSVP tunnels to reach the destination PE routers. With properly placed redundant links between the PE routers, this

provides MPLS FRR capability between PE and P routers without the need of a full mesh end to end RSVP tunnels between the PE routers.

As a backup to RSVP, LDP can be used to build a full mesh of LSPs among the PE, ASBR and RR routers.

LDP must be enabled on all of the following:

• Links from PE to P routers

• Links from ASBR to P routers

• Links from RR to P routers

• Links connecting two PE routers at the same POP

• Links connecting two P routers at the same POP

• Via tunnelling over all RSVP LSPs connecting to P routers

LDP uses the IGP to determine the path used, and also counts on the convergence of the IGP in the event of a failure. In the event of a failure on a PE/ASBR/RR to P router link the recovery of the LSP will be dependent on the IGP convergence around the failure.