Up to now in this section, we've mostly looked at the network layer's forwarding function. We studied that when a packet arrives to a router, the router indexes a forwarding table and determines the link interface to which the packet is to be directed. We also studied that routing
"Internet Control Message Protocol (ICMP)" covered IPv4 in some detail, containing the services it provides and how those services are implemented. While reading through that section, you may have noticed that there was no mention of any security services. In fact, IPv4 was
As we have seen the technical details of IPv6 let us look at a very practical matter: How will the public Internet, which is based on IPv4, be transitioned to IPv6? The problem is that while new IPv6-capable systems can be made backward-compatible, that is, can send, route, and
In the early 1990s, the Internet Engineering Task Force began an effort to develop a successor to the IPv4 protocol. A prime motivation for this effort was the realization that the 32-bit IP address space was beginning to be used up, with new subnets and IP nodes being attached to
Remember that the network layer of the Internet has three main components: the IP protocol, discussed in the previous section; the Internet routing protocols (including RIP, OSPF. and BGP), which are covered in Routing in the Internet and ICMP, which is the subject of this section.
After studying Internet addresses and the IPv4 datagram format, we're now well aware that every IP-capable device requires an IP address. With the proliferation of small office, home office (SOHO) subnets, this would seem to imply that whenever a SOHO wants to install a LAN to
In order to get a block of IP addresses for use within an organization's subnet, a network administrator might first contact its ISP. which would provide addresses from a larger block of addresses that had already been assigned to the ISP. For instance, the ISP may itself have been
We’ll now concentrate on IPv4 addressing. Though you may be thinking that addressing must be a straightforward topic, hopefully by the end of this section you'll be convinced that Internet addressing is not only a juicy, subtle, and interesting topic but also one that is of central
Well study in "The Link Layer and Local Area Networks" that not all link-layer protocols can carry network-layer packets of the same size. Some protocols can carry big datagrams, whereas other protocols can carry only little packets. For instance, Ethernet frames can carry up to
Our discussion of network-layer addressing and forwarding thus far has been without reference to any particular computer network. In this section, we'll turn our attention to how addressing and forwarding are done in the Internet. We'll see that Internet addressing and forwarding