The Illustrated Network- P20:In this chapter, you will learn about the protocol stack used on the global public Internet and how these protocols have been evolving in today’s world. We’ll review some key basic defi nitions and see the network used to illustrate all of the examples in this book, as well as the packet content, the role that hosts and routers play on the network, and how graphic user and command line interfaces (GUI and CLI, respectively) both are used to interact with devices. | CHAPTER 5 Address Resolution Protocol 159 Reply to InARP message 2 My IP address is in the ARP reply . use this in the routing table. FIGURE Inverse ARP InARP exchange over a frame relay network. In this case the hardware address DLCI is known and the sender needs to determine the IP address. of logical connection at the frame frame relay or cell ATM level instead of MAC addresses. The issue in frame relay and ATM both called non-broadcast multiaccess NBMA link networks is to find the virtual circuit number such as the Data Link Connection Identifier DLCI in frame relay associated with a particular IP address. InARP Inverse ARP was developed for use on frame relay networks. Instead of using ARP to determine MAC-layer LAN addresses TCP IP networks linked by frame relay networks use InARP to determine the IP address at the other end of a frame relay DLCI number to use when sending IP packets. InARP is used as soon as frame relay DLCI are created. The replies are used to build the routing table in the frame relay access device router . The InARP process is shown in Figure . InARP is essentially an adaptation of the reverse ARP RARP process used on LANs. ATMARP is a similar method used to find the ATM virtual path identifier VPI and or virtual channel identifier VCI over an ATM network. ARP AND IPv6 IPv6 really has no need for a separate ARP function. Instead the Neighbor Discovery protocol ND sometimes NDP described in RFC 2461 performs the functions of the IPv4 ARP in IPv6. ND is really a superset of most of the functions of IPv4 s ARP ICMP Redirect and ICMP Router Discovery features. This section will discuss some of the features of NDP but most of this will be covered in the chapter on ICMP. 160 PART II Core Protocols Neighbor Discovery Protocol The Neighbor Discovery protocol is the way that IPv6 hosts and routers find things out about their immediate neighborhood typically the LAN segment. A lot of effort was expended in IPv4 to find out configuration .
