As IP (and especially Internet) traffic grew exponentially
in the mid-1990s, it became an ever greater consumer of the SDH/SONET or ATM infrastructure,
but with routers using general-purpose microprocessors to forward traffic,
there was still a speed gap between the fastest IP interface and that of the long-haul
transport systems. However, by the late 1990s, routers became available with ASICbased
forwarding able to fill the 2.5 Gbps and 10 Gbps links provided by transport
systems, making it possible to bypass the ATM and SDH layers.
New entrant carriers with ???all-IP??? networks now faced a challenge in offering ATM
and Frame Relay services over their networks because IP networks supported connectionless
Layer 3 service rather than connection-orientated Layer 2 service. However
MPLS, with its mix of connectionless and connection-orientated characteristics, was
increasingly being used both to offer IP VPN services and to enable traffic engineering
for IP core networks and could easily be extended to offer Layer 2 services.
One early solution to offering Layer 2 services over MPLS was Juniper??™s Circuit
Cross Connect (CCC). With CCC, an LSR associated a pair of RSVP-TE signalled LSPs
(one for which it was ingress and one for which it was egress) with an attachment circuit
(either a physical interface or a logical interface such as a port and VLAN).
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