tcp timestamp
Description
Protocol suite: TCP/IP.
Protocol type: Transport layer protocol.
Option length: 10 bytes.
The TCP Timestamp option obsoletes the TCP Echo request and Echo reply options.
RFC 1323:
The timestamps are used for two distinct mechanisms: RTTM (Round Trip Time Measurement) and PAWS (Protected Against Wrapped Squences).
结构图
Kind. 8 bits. Set to 8.
Length. 8 bits. Set to 10.
Timestamp Value (TSval). 32 bits.
This field contains the current value of the timestamp clock of the TCP sending the option.
TImestamp Echo Reply (TSecr). 32 bits.
This field only valid if the ACK bit is set in the TCP header. If it is valid, it echos a timestamp value that was sent by the remote TCP in the TSval field of a Timestamps option. When TSecr is not valid, its value must be zero. The TSecr value will generally be from the most recent Timestamp option that was received; however, there are exceptions that are explained below. A TCP may send the Timestamp option in an initial SYN segment(i.e., segment containing a SYN bit and no ACK bit), and may send a TSopt in other segments only if it received a TSopt in the initial SYN segment for the connection.
Linux内核中的使用
如果支持Timestamp选项,那么可以用此选项来计算RTT。
static void tcp_ack_saw_tstamp(struct sock *sk , int flag)
{
/* RTTM Rule: A TSecr value received in a segment is used to
* update the averaged RTT measurement only if the segment
* acknowledges some new data, i.e., only if it advances the
* left edge of the send window.
*
* Changed: reset backoff as soon as we see the first valid
* sample. If we do not, we get strongly overestimated rto.
* With timestamps samples are accepted even from very
* old segments: f.e., when rtt=1 increases to 8, we retransmit
* 5 times and after 8 seconds delayed answer arrives rto
* becomes 120 seconds!
*/
struct tcp_sock *tp = tcp_sk(sk);
tcp_valid_rtt_meas(sk, tcp_time_stamp - tp->rx_opt.rcv_tsecr);
}
rtt即等于现在的时间tcp_time_stamp减去Timestamp Echo Reply,即tp->rx_opt.rcv_tsecr。
TCP timestamp option的作用:
1)allow more accurate round-trip time measurements for deriving the retransmission timeout estimator.
2)protect against old segments from the previous incarnations of the TCP connection.
3)allow detection of unnecessary retransmissions.
tcp_tw_recycle/tcp_timestamps都开启的条件下,60s内同一源ip主机的socket connect请求中的timestamp必须是递增的。
原文
http://blog.csdn.net/zhangskd/article/details/7195795
tcp_tw_recycle和tcp_timestamps导致connect失败问题
http://blog.sina.com.cn/s/blog_781b0c850100znjd.html
tcp timestamp的更多相关文章
- TCP连接建立系列 — 客户端的端口选取和重用
主要内容:connect()时的端口选取和端口重用. 内核版本:3.15.2 我的博客:http://blog.csdn.net/zhangskd 端口选取 connect()时本地端口是如何选取的呢 ...
- TCP 、UDP、IP包的最大长度
1.概述 首先要看TCP/IP协议,涉及到四层:链路层,网络层,传输层,应用层. 其中以太网(Ethernet)的数据帧在链路层 IP包在网络层 TCP或UDP包在传输层 TCP或UDP中的数据(Da ...
- Multipath TCP and load balancers
Load balancers play a very important role in today’s Internet. Most Internet services are provided b ...
- TCP中RTT的测量和RTO的计算
https://blog.csdn.net/zhangskd/article/details/7196707 tcp传输往返时间是指:发送方发送tcp断开时, 到发送方接收到改段立即响应的所耗费的时间 ...
- tcp timewait 问题 转载
TIME WAIT 带来的问题 先引用一个名言: The TIME_WAIT state is our friend and is there to help us (i.e., to let old ...
- 【Azure 应用服务】Azure Web App的服务(基于Windows 操作系统部署)在被安全漏洞扫描时发现了TCP timestamps漏洞
问题背景 什么是TCP timestamps(TCP 时间戳)? The remote host implements TCP Timestamps, as defined by RFC1323 (h ...
- TCP服务端收到syn但是不回复syn ack问题分析
文章转载自:https://blog.csdn.net/jueshengtianya/article/details/52130667 最近在分析客户的一个问题时遇到了一种奇怪的情况,客户在服务端开启 ...
- 【lwip】12-一文解决TCP原理
目录 前言 12.1 TCP协议简介 12.2 TCP相关的一些概念词 12.2.1 MSL 12.2.2 MSS 12.3 TCP工作特性 12.3.1 面向连接 12.3.2 全双工通信 12.3 ...
- hping原理、安装、使用详解介绍
[原理基础] Hping是一个命令行下使用的TCP/IP数据包组装/分析工具,其命令模式很像Unix下的ping命令,但是它不是只能发送ICMP回应请求,它还可以支持TCP.UDP.ICMP和RAW ...
随机推荐
- bug_ _java.lang.IllegalArgumentException: View not attached to window manager 2
今天遇到一个很奇特的问题,当用户设置了PIN码,在锁屏界面正常解锁PIN码后,进入Launcher时显示com.android.phone 已停止运行.一开始猜想会不会是解锁PIN码的时候处理导致了P ...
- Bridge桥接模式
当我们的功能要在多个维度进行扩展时,各个维度之间可以交叉组合,就可以考虑使用桥接模式. 将抽象部分与实现部分分离,使它们都可以独立的变化. ...
- C++学习47 文件的概念 文件流类与文件流对象 文件的打开与关闭
迄今为止,我们讨论的输入输出是以系统指定的标准设备(输入设备为键盘,输出设备为显示器)为对象的.在实际应用中,常以磁盘文件作为对象.即从磁盘文件读取数据,将数据输出到磁盘文件.磁盘是计算机的外部存储器 ...
- js监听浏览器关闭事件
html : <HTML> <HEAD> <title>test</title> </HEAD> <body onbefore ...
- AngularJs编写指令
<!DOCTYPE html> <html ng-app="app"> <head lang="en"> <meta ...
- java类总结
1.java类与类之间存在六种关系:继承,实现,依赖,关联,聚合组成 2.一个类可以继承另外一个类,并在此基础上添加自己的特有的功能. 3.一个类的方法中操作另外一个类的对象,这种情况称为第一个类依赖 ...
- ubuntu实用技巧
添加alias ~/.bash_alias文件: alias go="python /Users/xhat/Downloads/goagent/local/proxy.py" ~/ ...
- XBox360-双光盘游戏自制GOD
一直在找极限竞速4(Forza4),虽然这个版本比较老,但因为带体感.终于下到了,可惜是2个ISO.试着自己做GOD.用到两个软件:Iso2God和Xbox Backup Creator(俗称XBC) ...
- 05-UIKit绘图演练
*:first-child { margin-top: 0 !important; } body > *:last-child { margin-bottom: 0 !important; } ...
- jdk线程常见面试题
请编写一个多线程程序,实现两个线程,其中一个线程完成对某个对象int成员变量的增加操作,即每次加1,另一个线程完成对该对象成员变量的减操作,即每次减1,同时要保证该变量的值不会小于0,不会大于1,该变 ...