VMware, Inc.
47
Chapter 5 Discovery
Choosing a Method of Dependency Discovery
Table 5
‐
3
outlines
the
differences
in
the
information
that
are
discovered
through
either
Passive
Discovery
(PD)
or
Detail
Discovery
(DD)
to
help
you
determine
which
type
to
use
in
your
environment.
Note
the
following
when
you
are
using
Passive
or
Detail
Discovery
for
discovering
dependencies:
If
the
same
connection
is
discovered
through
both
Passive
and
Detail
Discovery,
the
connection
is
reconciled
to
appear
as
a
single
connection;
for
example,
if
Passive
Discovery
discovers
the
protocol,
activity
and
the
server
‐
side
service,
and
Detail
Discovery
discovers
the
client
‐
side
service,
the
two
discoveries
would
be
reconciled
to
include
all
the
information
collected
by
both
discovery
types,
without
redundancy.
The
process
of
reconciling
hosts
might
take
some
time.
ADM
uses
the
same
Passive
Discovery
scope
IP
filters
to
filter
remote
hosts
(hosts
connected
to
the
interrogated
host)
discovered
during
Detail
Discovery.
This
feature
avoids
the
problem
of
Detail
Discovery
overriding
the
IP
ranges
that
were
excluded
as
part
of
the
Passive
Discovery
scope.
By
default,
Detail
Discovery
policies
do
not
discover
network
dependencies
due
to
issues
surrounding
performance.
The
discovery
of
network
dependencies
substantially
increases
the
amount
of
time
it
takes
to
reconcile
the
discovered
results,
and
since
the
default
deployment
of
ADM
includes
Passive
Discovery,
this
default
configuration
still
provides
a
full
view
of
the
network,
including
network
dependencies.
vCollector
support
Passive
Discovery
only.
Discover
the
open
ports
that
the
services
running
on
the
interrogated
host
are
using
to
listen
for
incoming
connections
(“service
endpoints”).
Both
netstat
and
SNMP
tables
expose
listening
ports
that
is
used
to
create
a
service
endpoint
with
that
port.
An
example
of
this
is
discovering
that
an
Apache
service
is
listening
on
ports
80
and
8080,
even
if
no
active
connection
exists
at
the
time
of
the
discovery.
Guess
the
top
‐
level
protocol
used
by
those
connections.
To
avoid
false
positives,
it
is
done
only
on
low
ports:
<512.
Table 5-2.
Dependency Discovering Methodology (Continued)
What
How
Table 5-3.
Comparison of Passive and Detail Discovery Information
Difference
Advantage
PD
DD
Detailed
discovered
dependencies
do
not
include
activity,
whereas
passively
discovered
dependencies
do.
Protocol
identification
is
by
far
more
accurate
with
Passive
Discovery.
This
of
course,
results
from
Passive
Discovery
ʹ
s
specialization
in
protocol
analysis.
Passive
Discovery
is
weak
in
discovering
the
source
of
a
connection
for
reasons
explained
in
“ADM
Dependency
Discovery
Methods”
on
page 46.
Passive
Discovery
cannot
discover
the
ports
on
which
a
service
is
listening
unless
a
client
sent
a
packet
to
it.
Detail
Discovery
discovers
connections
that
are
active
at
the
time
of
discovery,
whereas
Passive
Discovery
samples
all
communication
traffic
on
the
network.
This
means
that
ephemeral
connections
have
less
of
a
chance
to
be
discovered
through
Detail
Discovery.
Note:
However
the
connections
that
are
active
and
representing
an
interaction
with
a
live
business
application
are
not
likely
to
be
ephemeral.
Only
Detail
Discovery
discovers
documented
dependencies
that
are
dependencies
discovered
by
looking
at
the
configuration
of
service,
such
as
in
the
files
and
registry.
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