TCP IP Illustrated

Each entry in the routing table contains the

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: ess, as specified by the flag field (described below) for this entry. A host address has a nonzero host ID (Figure 1.5) and identifies one particular host, while a network address has a host ID of 0 and identifies all the hosts on that network (e.g., Ethernet, token ring). IP address of a next-hop router, or the IP address of a directly connected network. A nexthop router is one that is on a directly connected network to which we can send datagrams for delivery. The next-hop router is not the final destination, but it takes the datagrams we send it and forwards them to the final destination. Flags. One flag specifies whether the destination IP address is the address of a network or the address of a host. Another flag says whether the next-hop router field is really a nexthop router or a directly connected interface. (We describe each of these flags in Section 9.2.) Specification of which network interface the datagram should be passed to for transmission. IP routing is done on a hop-by-hop basis. As we can see from this routing table information, IP does not know the complete route to any destination (except, of course, those destinations that are directly connected to the sending host). All that IP routing provides is the IP address of the nexthop router to which the datagram is sent. It is assumed that the next-hop router is really "closer" to the destination than the sending host is, and that the next-hop router is directly connected to the sending host. IP routing performs the following actions: 1. Search the routing table for an entry that matches the complete destination IP address (matching network ID and host ID). If found, send the packet to the indicated next-hop router or to the directly connected interface (depending on the flags field). Point-to-point links are found here, for example, since the other end of such a link is the other host's file:///D|/Documents%20and%20Settings/bigini/Docum.../homenet2run/tcpip/tcp-ip-illustrated/ip_inter.htm (6 of 19) [12/09/2001 14.46.37] Chapter 3. IP: Internet Protocol complete IP address. 2. Search the rout...
View Full Document

Ask a homework question - tutors are online