Question

Routing table is consulted to decide

Answer 1

2) Routing tables....

A routing table, or routing information base (RIB), is an electronic file or database-type object that is stored in a router or a networked computer, holding the routes (and in some cases, metrics associated with those routes) to particular network destinations. This information contains the topology of the network close to it. Construction of these tables is the primary task of routing protocols and static routes. They are generally not used directly for packet forwarding in modern router architectures; instead, they are used to generate the information for a smaller forwarding table which contains only the routes which are chosen by the routing algorithm as preferred routes for packet forwarding, often in a compressed or pre-compiled format that is optimized for hardware storage and lookup.

An example routing table is given in Figure 11.6. In part A, the first row of the table states that network 10.0.10.0 is on interface “Eth0” and the “C” in the “Learned” column means the information was learned through a direct connection; in other words, the network is local to the router. The last row states that network 10.0.21.0 is on interface “S0” and the “R” in the “Learned” column means the information was learned through a routing protocol; in this case, the network is not local to the router..

Routing Table in each Host

The information in Routing table is used for the host to verify when it helps transferring a packet to the destination of the packet. While receiving a packet, the host verifies the identifier of the destination host. When a record in the routing table has the same destination, the host gets the identifier of next host and the delay constraint in the field and dc field of the routing path, respectively. Thus the host knows the receiver of this packet and the constraint of delay transferring. To guarantee the delay constraint of a packet, the delay time of each transmission should be limited in a certificated duration, namely, delay constraint of the transmission. As we have mentioned, a host can have the total delay time and the delay constraint of the transmission from the source to the destination in DU field of RREP and DC field of RREQ, respectively. The delay time of the host to its next neighbor is obtained according to the dt field of RREP. Therefore we calculate the delay constraint if a host receives an RREP and is the source of the RREP packet. It also records the routing Map of the routing path in SL field. After the double of the packets' DC, the source host reorganizes all the routing paths that are illustrated in the next section.....

#ANONYMOUS

.. $$$