Alcatel 1660SM Technical Handbook page 251

Main functional aspects of the ISA–PR:
1660SM when equipped with ISA–PR sub–system will allow point–to–point and multipoint–to–multipoint
Metro Ethernet connections between routers or switches through SDH, as depicted Figure 14.
The Packet Ring maps Ethernet over MPLS over POS and shares the bandwidth between hundreds of
Ethernet traffic flows according to the defined SLA.
The bandwidth in this Packet Ring may, and likely will, be oversubscribed; hence sophisticated traffic
management functions are provided to ensure the service SLAs are adhered to.
All the Ethernet access connectors are on the front panel of the 2GBA–PR and 16FEA–PR cards.
A full–blown configuration constitutes two or three cards.
An ISA–PR Port card and at least one of either an 2GBA–PR and/or 16FEA–PR Access card, which
provide various combinations of 10/100 and GbE interfaces.
ISA–PR "Overlay" Packet Ring provides:
•
Layer 1 – STM–4 (or dual STM–4)
•
Layer "1.5" – MPLS over PPP/HDLC Packet Ring multiplexed over VC–4–4v, VC–4–6v and
VC–4–8v
•
Ring protection is executed at the overlay L1.5 level
•
Ring operational modes: Uni–directional and [future] Bi–directional
The ISA–PR Ethernet Packet Ring bandwidth is constructed from a virtually concatenated SDH path in
the form VC–4–xv (where x=4, 6, 8). This Packet Ring provides sub–50ms protection by employing packet
wrapping to ensure restoration or traffic under ring or node failure conditions.
The ISA–PR board provides the operator with the flexibility to provision the mapping between the ISA–PR
port STM–4 interfaces and the SDH Ring; in this way the operator can choose the mapping which he thinks
more appropriate:
ISA–PR provides the following concatenation options over a single STM–4 interface:
•
VC–4–4c over a single STM–4 interface
•
VC–4–4v over a single STM–4 interface
ISA–PR provides the following concatenation options over dual STM–4 physical interfaces:
•
VC–4–6v over two STM–4 interfaces
•
VC–4–8v over two STM–4 interfaces
Ethernet frames arriving onto the ports of an 2GBA–PR and 16FEA–PR Access card are firstly classified
to determine priority and destination, placed in the appropriate priority queue and then mapped, according
to SLA rules, into the Packet Ring via the ISA–PR Port card – the mapping used is
Ethernet/MPLS/POS/SDH.
The output of the ISA–PR port card uses either two or four STM–4 optical outputs, which are connected
externally (via optical cable) into one or more 1660 SM STM–4 tributary cards toward the SDH matrix, then
through the back–Plane and finally out onto the physical SDH ring as an overlay embedded Packet Ring.
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