第四章IPv6 v2.ppt

新一代互联网网络层协议IPv6 徐恪 清华大学计算机系 Outline Protocol Background Technology Highlights Enhanced Capabilities Transition Issues Next Steps 新一代互联网的定义和主要特征 目前还没有统一的严格定义，新一代互联网将是一个渐进的发展过程 目前已取得共识的主要特征 更大：IPv6的地址空间，网络的规模更大，接入网络的终端种类和数量更多，网络应用更广泛 更快：100Mbps以上的端到端高性能通信 更安全可信：对象识别，身份认证和访问授权，数据加密和完整性，基于真实IPv6源地址的可信任网络 更及时：组播服务，服务质量（QoS），大规模实时交互应用 更方便：基于移动和无线通信的丰富应用 更可管理：有序的管理、有效的运营、及时的维护 更有效：有盈利模型，获得重大社会效益和经济效益 Why a New IP? 1991 – ALE WG studied projections about address consumption rate showed exhaustion by 2008 Bake-off in mid-1994 selected approach of a new protocol over multiple layers of encapsulation What Ever Happened to IPv5? 0 IP March 1977 version (deprecated) 1 IP January 1978 version (deprecated) 2 IP February 1978 version A (deprecated) 3 IP February 1978 version B (deprecated) 4 IPv4 September 1981 version (current widespread) 5 ST Stream Transport (not a new IP, little use) 6 IPv6 December 1998 version (formerly SIP, SIPP) 7 CATNIP IPng evaluation (formerly TP/IX; deprecated) 8 Pip IPng evaluation (deprecated) 9 TUBA IPng evaluation (deprecated) 10-15 unassigned Technologies efforts to slow the consumption rate Dial-access / PPP / DHCP Provides temporary allocation aligned with actual endpoint use Strict allocation policies Reduced allocation rates by policy of “current-need” vs. previous policy based on “projected-maximum-size” CIDR Aligns routing table size with needs-based address allocation policy. Additional enforced aggregation actually lowered routing table growth rate to linear for a few years NAT Hides many nodes behind limited set of public addresses Would increased use of NATs be adequate? NO! NAT enforces a “client-server” application model where the server has topological constraints They won’t work for peer-to-peer or devices that are “called” by others (e.g., IP phones) They inhibit deployment of new applicatio