Cisco 7000 Series Hardware Installation And Maintenance page 77

Network Connections
Preparing
NRZ
and NRZI Formats
All data
inverted
signals
during
signal
and the absence
than
determining
All interface
IBM
Redundancy Checks
Cyclic
All data
support
detect
predetermined
frame
the
divisible
predetermined
assumes
The
designators
FCS
the
Thirty-two
32-bit
retransmits
less
Sixteen-bit
used
extensively
point-to-point
LANs
instructions
Modes
and
Signal Timing
Data communications
the clock
DCE
In
router
must
use
speed
DTE
In
remote
modem
as
DCE
cables
remote
Occasionally
transmission
can cause
shift
clock
Cisco 7010 Hardware
2-26 Installation
communications
interfaces
NRZI formats Both
formats
maintain
constant
voltage
and decoded
bit interval
are
but the presence
levels
interprets
of data
no
transition
as
absolute
values
NRZI
also
types support
environments See
Configuring
CRCs
communications
interfaces
CRC
CRC
32-bit
an
is
The
in transmitted data
errors
number
calculate
to
the sender
the
appends
number
by the
predetermined
number
the sender
that
eior
transmission
that
16 and
32 indicate
CRC
which
Sixteen-bit
CRC
which
transmits
bit
CRC
transmits streams
longer
Both and
the sender
CRC
most
the
is
widely
with wide-area networks
transmission standards
See
32-Bit
Configuring
Cyclic
ports operate
the port
that
uses
signal
mode
the port supplies
its
DTE
PC
device such
to as
DCE
cable and
adapter
which
mode
the most commonly
is
or external You
device
normally
CSUIDSU DTE
Most
or
To
device
provides set
up
When
the port recognizes
DCE
device
with long cables
systems
speeds Slight variances
the clock and data
signals
FSIP
an
If
port reporting
is
with the invert-transmit-clock
and Maintenance
both nonreturn
support to
two
use
different voltage
no
with
levels transitions
signal
using absolute values
of data the beginning
at
NRZI
uses
differential
NRZ
default
the on
factory
which
format commonly
is
NRZI Format
in Chapter
use
16-bit cyclic
redundancy
that
error-checking
technique
frame
sender of data divides
remainder check
orfraine
FCS
value
to the
message so
The
receiver divides the
FCS
used calculate the
to
and
occurred sends
request
number check
of
the
digits
transmits streams of
8-bit
characters
streams of
16-bit
characters
at faster rates
it
provides
the receiver must use the
method
used the United
throughout
WANs
IEEE-802
an
it as
specify option It
CRC
Check
Redundancy
DCE DTE mode
in either
or
and the mode
remote
of the device
own
You
clock
signal normally
host To
or another router
use the clockrate
configuration
mode
used port uses
the
DTE
when
use
connecting
an external
interfaces require
DTE
you need
port as interface
DTE
the cable
it automatically
high error
may
experience
in
cable
construction
temperature
to shift
out of phase
Inverting
number
of
error packets
high
command
NRZ
and nonreturn
zero to
NRZ
for transmission
levels
no
return
to
zero voltage
NRZI
and uses the
same
of
bit interval signal transition
as
decode
to
encoding signals
common
most
interface
all types is
RS-232
used with connections
for configuration instructions
CRC
check
default
by
numeric
calculated value
uses
frame
the the
bits in
message
FCS
Before
it
sequence
frame
that the
contents are exactly
frame
by the
same
contents
receiver
If the result is not the
the sender resend
the
to to
frame
are used
that calculate
to
per
FCS
16-bit
generates
FCS
32-bit
generates
better detection
ongoing error
same
setting
and
Europe
States
CRC
32-bit
some
and
specifies
SMDS
often used on networks
is
for configuration
in
Chapter
mode
the of source
depends the
which connected
the port
to
is
DCE
when
use
connecting
DCE
set up port as interface
command
the
to set internal
clock
signal supplied
DCE
router device
the to
which
clock the remote
signal
DTE
connect
only adapter
from
uses the clock
signal
when
the higher
rates at
operating
and network
configuration
clock can often correct
the
and invert
shift
phase
suspect
zero
level
constant
rather
in
but also
to
by
sends
frame
Because
with
and
it is
and
of
the
you
clock
by
such
the
this
the