Released
PMC-Sierra, Inc.
PM9311/2/3/5 ETT1™ CHIP SET
Data Sheet
PMC-2000164
ISSUE 3
ENHANCED TT1™ SWITCH FABRIC
1.1.2 The Switch Core Model
The ETT1 Chip Set is designed to provide a switch core, not a complete packet switch system. A complete
switch consists of one or more switch cores, together with a number of linecards. Each linecard connects
to one port in the core. The linecard includes a physical interface (fiber, co-axial cable) to a transmission
system such as SONET/SDH or Ethernet. The linecard analyzes incoming cells or packets and determines
the appropriate egress port and priority. The linecard contains any cell/packet queues that are needed to
allow for transient congestion through the switch.
The ETT1 switch core operates on fixed size cells. If the linecard transmission system uses variable length
packets, or cells of a size different from those used in the core, then the linecard is responsible for
performing any segmentation and reassembly that is needed. Figure 1 illustrates this generic
configuration.
Figure 1. The Basic Components of a Switch Built Around the ETT1 Chip Set.
ETT1 Switch Core
port 0
ETT1 Chip Set
Linecard 0
SONET/SDH
Ethernet....
Linecard 31
SONET/SDH
Ethernet....
port 0
OOB Bus
LCS Protocol
CPU
The ETT1 Chip Set has been designed to allow for up to 200 feet (70 meters) of physical separation
between the ETT1 core and the linecard. The LCSTM(Linecard to Switch) protocol is used between the
ETT1 core and the linecard to ensure lossless transfer of cells between the two entities. However, while
the LCS protocol must be implemented, the physical separation is not mandatory; the linecard could reside
on the same physical board as the ETT1 port devices.
The switch core has two main interfaces. One is the interface between the linecard and the core port,
described in the LCS Protocol section.
16
PROPRIETARY AND CONFIDENTIAL TO PMC-SIERRA, INC., AND FOR ITS CUSTOMERS’ INTERNAL USE
PMC [ PMC-SIERRA, INC ]
