Problem 6
1.
The routing function attempts to find the least-cost route through the network, with
cost based on
number of hops, expected delay, or other metrics
2.
Adaptive routing algorithms typically rely on the
exchange of information about
traffic conditions among nodes.
3.
Routing
decisions
are
made
on
the
basis
of
some
performance
criterion.Two
key
characteristics of the decision are the
time and place that the decision is made.
4.
Decision time
is determined by whether the routing decision is made on a packet
or
virtual
circuit
basis.
When
the
internal
operation of
the
network
is datagram,
a
routing
decision is made
individually for each packet. For internal virtual circuit operation, a routing
decision is made at the time
the virtual circuit is established.
5.
The
term
decision
place
refers
to
which
node
or
nodes
in
the
network
are
responsible for the routing decision. For
distributed routing
, in which each node has the
responsibility of selecting an output link for routing packets as they arrive. For
centralized
routing
, the decision is made by some designated node,such as a network control center.
6.
The
routing algorithm
is that part of the network layer software responsible
for deciding which output line an incoming packet should be transmitted on.
7.
A router has two processes inside it. One of them handles each packet as it arrives,
looking up the outgoing line to use for it in the routing tables. This process is
forwarding
.
The other process is responsible for
filling in and updating the routing tables. That is where
the routing algorithm comes into play.
8.
Nonadaptive algorithms
do not base their routing decisions on measurements
or
estimates
of
the
current
traffic
and
topology.
Instead,
the
choice
of
the
route
to
use
is
computed
in
advance,
off-line,
and
downloaded
to
the
routers
when
the
network
is
booted.
This procedure is sometimes called
static routing
.
9.
Adaptive
algorithms
,
change
their
routing
decisions
to
reflect
changes
in
the
topology, and usually the traffic as well.
10.
Flooding
is
the
technique
requires
no
network
information
whatsoever
and
works as follows. A packet is sent by a source node to every one of its neighbors. At each
node, an incoming packet is retransmitted on all outgoing links except for the link on which it
arrived.
11.
Dijkstra's
algorithm
is
a
graph
search
algorithm
that
solves
the
single-source
shortest path problem for a graph with non-negative edge path costs, producing a shortest path
tree. The shortest path algorithm
is widely used in network routing protocols, most
notably
IS-IS
and
OSPF (Open Shortest Path First).
12.
The Bellman-Ford algorithm
can be stated as follows: Find the shortest paths
from a given source node subject to the constraint that the paths contain at most one link, then
find the shortest paths with a constraint of paths of at most two links, and so on.
13.
The
routers
in
an
internet
are
responsible
for
receiving
and
forwarding
packets
through
the
interconnected
set
of
networks.
Each
router
makes
routing
decision
based
on
knowledge of the topology and traffic/delay conditions of the internet.
14.
Routing
information
is
Information
about
the
topology
and
delays
of
the
internet.
Routing algorithm
is The algorithm used to make a routing decision for a particular
datagram, based on current routing information.