tailieunhanh - The Illustrated Network- P18

The Illustrated Network- P18: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 4 IPv4 and IPv6 Addressing 139 The current policy is given at policy. An older policy is used in this chapter see policy and uses these prefixes at each step of the process 2001 16 is reserved for IANA. IANA hands out a 23 prefix to each registry. Registry hands out a 32 or shorter prefix to an IPv6 ISP. ISP allocates a 48 prefix for each customer site. Local administrators add 16 bits for each LAN on their network for a 64 prefix. This scheme is shown in Figure . When the LAN is included most IPv6 addresses have 64 network masks. This is the prefix length used on the Illustrated Network. IPv6 routers can perform the following tasks Route traffic to a particular ISP based on the first 32 bits of the IPv6 destination address. Route traffic to a particular site based on the first 48 bits of the IPv6 destination address. Route traffic to a particular LAN based on the first 64 bits of the IPv6 destination address. In practice IPv6 core routers can look at and build forwarding tables based on 32 or shorter prefixes routers inside a particular AS routing domain can look at 48 prefixes and site routers on the customer edge can look at 64 prefixes to get traffic right to the destination LAN. 128 bits One IPv6 Address Allocation Policy FIGURE IPv6 address allocation showing how various bits should be assigned by different entities. In some places mobile phone providers are heavy users of IPv6 addresses. 140 PART II Core Protocols Now we can better understand the IPv6 address assigned to CEO that we saw at the beginning of the chapter FC00 ffb3 d5 b 205 85ff fe88 ccdb or FC00 FFB3 00D5 000B 0205 75FF FE88 CCDB Let s break it down one element at a time and see where it all comes from Registry We use FC00 instead of 2001 to indicate a private ULA-local IPv6 address. ISP We add Best ISP s AS number of 65459 0xFFB3 for LAN 1 or Ace ISP s AS number 65127 0xFE67 for LAN2. Site We add telephony area code 213 0x00D5 for the .