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The LightSand S-2500B Gateway extends LAN connectivity over SONET via its Gigabit
Ethernet (GbE) port with the same quality of service as used for FC. Data is never dropped due
to congestion, and therefore never needs to be retransmitted. The IP over SONET feature turns
the network backbone into an Ethernet segment of unequaled reliability for attached servers
and clients.
Overview of the S-2500B Gateway
One S-2500B Gateway connects all of the FC switches in one SAN island to another SAN
island. The physical interfaces are SONET (OC-48), Gigabit Ethernet (GbE) and/or Fibre
Channel (FC). Each LightSand S-2500B Gateway is shipped with a set of control software pre-
installed, including the CLI (Command Line Interface).
SONET Interface
The SONET interface for the S-2500B Gateway is an industry standard OC-48 signal. This
provides a protected bandwidth allocated between the two point-to-point gateways. The
gateway maps the FC/GbE signals to STS-48c using end-to-end flow control that has been
optimized to provide full FC throughput at OC-48 rates over distances of thousands of
kilometers. A single encapsulation method, FC/POS, is all that is required for transferring data.
FC/POS
The S-2500B Gateway supports direct mapping of FC frames onto SONET, with no
intermediate mapping of FC onto IP. Because all FC frames are directly coupled onto SONET,
the S-2500B is directly connected via SONET to another S-2500B with no intervening IP
routers.
Flow Control
The S-2500B Gateway supports industry standard FC flow control on the FC ports as defined
in NCITS FC-SW-2 and FC-FS.
IP Routing
The S-2500B Gateway provides encapsulation of IP to route native IP traffic. In its function as
an IP router (actually a layer 3 switch), the S-2500B Gateway supports RIPv2.
The S-2500B Gateway has the ability to react to back pressure created by a PAUSE command
issued to the GbE port. The gateway, in turn, creates back pressure across the WAN/SONET
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S-2500B Gateway
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