This is analogous
to the inter-provider IP-VPN ???option A,??? as defined in RFC 4364, and although
simple and secure, the two providers must agree on VLANs at the inter-connect and
provision a new VLAN for each new service. This method also presents a single point
of failure at the interconnect, though this can be alleviated somewhat by using pairs of
GigE ports running 802.3ad link bundling over redundant fibre paths.
The MEF is working on a standardised Ethernet NNI to address the lack of standards
support for inter-provider Ethernet services, but in the interim many providers are looking
to use MPLS-derived mechanisms for interconnects. MS-PWs may be used, with
the border routers between two providers??™ networks both acting as S-PEs. The pseudowire
segment between the two border routers may be provisioned either statically or
using LDP. BGP may be used by the border routers to discover which pseudowires to
signal across the interconnect. See Figure 14.7 and the section below on dynamic multisegment
pseudowires for more discussion on the use of BGP for establishing MS-PWs.
Figure 14.7 Inter-provider Ethernet service using multi-segment pseudowire
Segment 1 Segment 2 Segment 3
Provider A network Provider B network
MPLS 455
For VPLS, the same mechanisms used for BGP autodiscovery may be extended to enable
service to be offered across two providers??™ networks in an analogous fashion to the interprovider
IP-VPN ???option B??? defined in RFC4364.
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