在TCP协议中,确认号(Acknowledgment Number)表示接收方期望收到的下一个字节的序列号。例如,若确认号为N,则说明接收方已正确接收N-1及之前的所有字节,并期望发送方接下来发送序列号为N的字节。因此:- **A) first**:错误。确认号不直接对应第一个字节,而是下一个期望的字节。- **B) last**:错误。确认号并...
tcpprobe显示的是TCP栈那里的情景,而tcpdump抓取的确实网卡边界的情景,中间隔了一个“qdisc”逻辑,即队列管理。也就是说TCP确实将732个数据段发出去了,因此它会认为其已经in flight了,但是这些数据并没有到达网上,而是到达了qdisc队列里面,考虑到是千兆网络同一网段的模拟,基本可以忽略传输延迟,因此tcpdump抓取的所谓...
我们学过TCP协议,知道TCP三次握手中的第一次生成的seq是随机生成的,接下来的数据的seq都是在首seq的基础上递增的,但是我们在收到数据后进行逻辑处理的时候,为了方便后续开发,我们引出了三个概念:初始序列号(initial sequence number)、相对序列号(relative sequence number)绝对序列号(absolute sequence number) 初始...
当anti-replay不生效的是,sender不再关心seq number,就一直加加加,然后溢出就变成0. 二 于是,这里有了一个新的问题, seq number满了就要重协商。看包我们发现这个字段是uint32的,所以,在高速网络中,每2^32个包就要重协商一次。 为了解决这个问题,现在引入一个新的概念,叫做:Extended Sequence Number(ESN) 见...
How to Do TCP Sequence Number Analysis May10 19 But more importantly, WHY you should do TCP sequence number analysis. Well, you know all those black and red packets in Wireshark? Sure, you’ve seen them, right? Scary, huh? What if someone says there’s a problem and you see a bunch...
—In this paper, we report a newly discovered "off- path TCP sequence number inference" attack enabled by firewall middleboxes. It allows an off-path (i.e., not man-in- the-middle) attacker to hijack a TCP connection and inject malicious content, effectively granting the attacker write-...
Making a trace of the Microsoft-Windows-TCPIP ETW provider when performing your tests might be helpful - the events reported by the TCP/IP stack in the trace might give some insight into the retransmission decisions. There are a number of features of the trace that seem interesting: MS...
Here’s a zoomed in screencap with some annotations: The x-axis is time. So this shows seconds e.g. 2.35 seconds. The y-axis is TCP sequence numbers. Sequence numbers are representative of bytes sent. The sequence number increases by 1 for every 1 byte of TCP data sent. Ideally you’...
The server responds to the client with a sequence number of zero, as this is its first packet in this TCP session, and a relative acknowledgment number of 1. The acknowledgment number is set to 1 to indicate the receipt of the client's SYN flag in packet #1. ...
In this study, we discover a new class of unknown side channels —“sequence-number-dependent” host packet counters — that exist in Linux/Android and BSD/Mac OS to enable TCP sequence number inference attacks. It allows a piece of unprivileged on-device malw...