ADDRESS MASKS
To identify receiver, network apply address mask to receiver address and calculate to network address in routing table. It can use Boolean 'and' to calculate the ith entry in the table.
i.e. if ((Mask[i] & D) == Dest[i] ) forward to NextHop[i]
FORWARDING, DESTINATION ADDRESS AND NEXT-HOP:
Receiver address in IP datagram is usually ultimate destination. Router looks up next-hop address and transfer datagram. Network interface layer operates on two parameters:
- IP datagram
- Next-hop address
Next-hop address never sees in IP datagram.
BEST-EFFORT DELIVERY:
IP gives service equivalent to LAN. It does not guarantee to save duplicate packets, out-of-order delivery or delayed, corruption of datagram loss and data. Transport layer gives reliable delivery. Network layer - IP - can checked and report errors without actually solving them. It focuses on packet delivery. Application layer is not interested in differentiating among delivery causes at intermediate routers.