TCP/IP 详解 卷1:协议(英文版)

本书特色

《TCP/IP详解.卷1:协议(英文版)》：图灵原版计算机科学系列

内容简介

本书是tcp/ip领域的经典之作！书中主要讲述tcp/ip协议，不仅仅讲述rfc的标准协议，而且结合大量实例讲述了tcp/ip协议族的定义原因，以及在各种不同的操作系统中的应用及工作方式，使读者可以轻松掌握tcp/ip的知识。本书内容详尽且具权威性，几乎每章都提供精选的习题，并提供了部分习题的答案。
　　本书适合任何希望理解tcp/ip协议如何实现的人阅读，更是tcp/ip领域研究人员和开发人员的权威参考书。无论是初学者还是功底深厚的网络领域高手，本书都是案头**。

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插图：The third and major reason is that the room allocated for options in the IP header isn't large enough today to handle most routes. There is room for only nine IP addresses in the IP header options field. In the old days of the ARPANET this was adequate, but it is far too small nowadays.Traceroute uses ICMP and the TTL field in the IP header. The TrL field （time-to-live） is an 8-bit field that the sender initializes to some value. The recommended initial value is specified in the Assigned Numbers RFC and is currently 64. Older systems would often initialize it to 15 or 32. We saw in some of the Ping examples in Chapter 7 that ICMP echo replies are often sent with the TrL set to its maximum value of 255.Each router that handles the datagram is required to decrement the TTL by either one or the number of seconds that the router holds onto the datagram. Since most routers hold a datagram for less than a second, the TrL field has effectively become a hop counter, decremented by one by each router.The purpose of the TTL field is to prevent datagrams from ending up in infinite loops, which can occur during routing transients. For example, when a router crashes or when the connection between two routers is lost, it can take the routing protocols some time （from seconds to a few minutes） to detect the lost route and work around it.During this time period it is possible for the datagram to end up in routing loops. The TTL field puts an upper limit on these looping datagrams.When a router gets an IP datagram whose TTL is either 0 or 1 it must not forward the datagram. （A destination host that receives a datagram like this can deliver it to the application, since the datagram does not have to be routed. Normally, however, no system should receive a datagram with a TTL of 0.） Instead the router throws away the datagram and sends back to the originating host an ICMP "time exceeded

作者简介

　　W. Richard Stevens 国际知名的UNIX和网络专家，备受赞誉的技术作家。他1951年2月5日出生于赞比亚，后随父母回到美国。中学时就读于弗吉尼亚菲什伯恩军事学校，1973年获得密歇根大学航空和航天工程学士学位。1975年至1982年，他在亚利桑那州图森市的基特峰国家天文台从事计算机编程工作，业余时间喜爱飞行运动，做过兼职飞行教练。这期间他分别在1978年和1982年获得亚利桑那大学系统工程硕士和博士学位。此后他去康涅狄格州纽黑文的健康系统国际公司任主管计算机服务的副总裁。1990年他回到图森，从事专业技术写作和咨询工作。写下了多种经典的传世之作，包括《TCP/IP详解》（三卷）、《UNIX环境高级编程》和《UNIX网络编程》（两卷）。Stevens于1999年9月1日去世，年仅48岁。2000年他被国际权威机构USENIX追授“终身成就奖”。