Juniper SYSTEM BASICS - CONFIGURATION GUIDE V 11.1.X

layered on top of physical (copper or optical) interfaces. The router supports a number
of access protocols (PPP/POS, Frame Relay, ATM) that allow service providers to
offer a number of access methods and line speeds to their subscribers. The router
is optimized to handle IP connections regardless of the access protocol used. The
router also supports a number of protocols that are specific to the B-RAS application.
These are shown in Figure 3 on page 7, and include IP/PPP/ATM and
IP/PPP/Ethernet/ATM.
Figure 3: Network Configuration Using a Bottom-Up Approach
Layer 2 (data link) defines how the data is packaged and sent to an IP data connection
point in layer 3 (IP interfaces). In layer 3, you define the global attributes for IP
services that serve as a platform from which you add routing information.
Line Modules, I/O Modules, and IOAs
A range of line modules, I/O modules, and I/O adapters (IOAs) are available for the
router. On the ERX14xx models, ERX7xx models, and the ERX310 router, most line
modules pair with a corresponding I/O module. On the E120 and E320 routers, a
single line module pairs with all available IOAs.
I/O modules and IOAs provide the input and output connections from the network
to the router. Line modules connect to their corresponding I/O modules or IOAs
through a passive midplane. A line module receives packets through its I/O module
or IOA and processes those packets. The router then routes the packets out to the
network through the designated I/O module or IOA.
Each line module, I/O module, and IOA has a label on its faceplate. In this
documentation, these modules are identified by that label. For example, the
high-density Gigabit Ethernet line module has two ports, and is called the GE-HDE
line module. Its corresponding I/O modules are the GE-HDE I/O module and the GE-2
SFP I/O module.
When we refer to a related set of line modules, I/O modules, or IOAs, the generic
information from the module labels is used in this documentation. For example, the
term “ OCx/STMx line modules” refers to both the OCx/STMx ATM and the OCx/STMx
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Chapter 1: Planning Your Network