EBK COMPUTER NETWORKING
7th Edition
ISBN: 8220102955479
Author: Ross
Publisher: PEARSON
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Question
Chapter 3, Problem P55P
a)
Program Plan Intro
Given scenario:
A server receives the request and responds a request within UDP packet. If a client with IP address “X” with address “Y”.
b)
Program Plan Intro
Given scenario:
The server receives a “SYN” with IP address “Y” and receives an acknowledgement “ACK” with IP address “Y”.
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Students have asked these similar questions
In this problem we investigate whether either UDP or TCP provides a degree of
end-point authentication.
a. Consider a server that receives a request within a UDP packet and responds to
that request within a UDP packet (for example, as done by a DNS server). If a
client with IP address X spoofs its address with address Y, where will the server
send its response?
b. Suppose a server receives a SYN with IP source address Y, and after responding
with a SYNACK, receives an ACK with IP source address Y with the correct
acknowledgment number. Assuming the server chooses a random initial sequence
number and there is no "man-in-the-middle," can the server be certain that the
client is indeed at Y (and not at some other address X that is spoofing Y)?
Using a TCP SYN spoofing attack, the attacker aims to flood the table of TCP connection requests on a system so that it is unable to respond to legitimate connection requests. Consider a server system with a table for 256 connection requests. This system will retry sending the SYN-ACK packet five times when it fails to receive an ACK packet in response, at 30 second intervals, before purging the request from its table. Assume that no additional countermeasures are used against this attack and that the attacker has filled this table with an initial flood of connection requests.
a. At what rate must the attacker continue to send TCP connection requests to this system in order to ensure that the table remains full?
b. Assuming that the TCP SYN packet is 40 bytes in size (ignoring framing overhead), how much bandwidth does the attacker consume to continue this attack?
Consider a simple UDP-based protocol for requesting files (based
somewhat loosely on the Trivial File Transport Protocol, or TFTP).
The client sends an initial file request, and the server answers (if
the file can be sent) with the first data packet. Client and server
then continue with a stop-and-wait transmission mechanism.
(a) Describe a scenario by which a client might request one file
but get another; you may allow the client application to exit
abruptly and be restarted with the same port.
(b) Propose a change in the protocol that will make this situation
much less likely.
Chapter 3 Solutions
EBK COMPUTER NETWORKING
Ch. 3 - Prob. R1RQCh. 3 - Prob. R2RQCh. 3 - Consider a TCP connection between Host A and Host...Ch. 3 - Prob. R4RQCh. 3 - Prob. R5RQCh. 3 - Prob. R6RQCh. 3 - Suppose a process in Host C has a UDP socket with...Ch. 3 - Prob. R8RQCh. 3 - Prob. R9RQCh. 3 - In our rdt protocols, why did we need to introduce...
Ch. 3 - Prob. R11RQCh. 3 - Prob. R12RQCh. 3 - Prob. R13RQCh. 3 - Prob. R14RQCh. 3 - Suppose Host A sends two TCP segments back to back...Ch. 3 - Prob. R16RQCh. 3 - Prob. R17RQCh. 3 - Prob. R18RQCh. 3 - Prob. R19RQCh. 3 - Prob. P1PCh. 3 - Prob. P2PCh. 3 - UDP and TCP use 1s complement for their checksums....Ch. 3 - Prob. P4PCh. 3 - Prob. P5PCh. 3 - Prob. P6PCh. 3 - Prob. P7PCh. 3 - Prob. P8PCh. 3 - Prob. P9PCh. 3 - Prob. P10PCh. 3 - Prob. P11PCh. 3 - Prob. P12PCh. 3 - Prob. P13PCh. 3 - Prob. P14PCh. 3 - Prob. P15PCh. 3 - Prob. P16PCh. 3 - Prob. P17PCh. 3 - Prob. P21PCh. 3 - Prob. P22PCh. 3 - Prob. P25PCh. 3 - Prob. P26PCh. 3 - Prob. P27PCh. 3 - Host A and B are directly connected with a 100...Ch. 3 - Prob. P29PCh. 3 - Prob. P30PCh. 3 - Prob. P31PCh. 3 - Prob. P33PCh. 3 - Prob. P34PCh. 3 - Prob. P35PCh. 3 - Prob. P37PCh. 3 - Prob. P38PCh. 3 - Prob. P39PCh. 3 - Prob. P41PCh. 3 - Prob. P42PCh. 3 - Prob. P43PCh. 3 - Prob. P44PCh. 3 - Prob. P45PCh. 3 - Prob. P46PCh. 3 - Prob. P47PCh. 3 - Prob. P48PCh. 3 - Prob. P49PCh. 3 - Prob. P51PCh. 3 - Prob. P53PCh. 3 - Prob. P55P
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Similar questions
- We explore whether either UDP or TCP offers any level of end-point authentication in this problem. a. Consider a server that accepts a request via UDP and responds via UDP (for example, as done by a DNS server). Where would the server give its answer if a client with IP address X spoofs it with address Y? b. Assume a server receives a SYN with IP source address Y and responds with SYNACK. The server then receives an ACK with IP source address Y and the right . acknowledgment amount. Assuming the server selects a random initial sequence number and there is no "man-in-the-middle," how can the server be confident that the recipient is really at Y (and not at any other address X that spoofs Y)?arrow_forwardWe explore whether either UDP or TCP offers any level of end-point authentication in this problem. a. Consider a server that accepts a request via UDP and responds via UDP (for example, as done by a DNS server). Where would the server give its answer if a client with IP address X spoofs it with address Y? b. Assume a server receives a SYN with IP source address Y and responds with SYNACK. The server then receives an ACK with IP source address Y and the right acknowledgmentamount. Assuming the server selects a random initial sequence number and there is no "man-in-the-middle," how can the server be confident that the recipient is really at Y (and not at any other address X that spoofs Y)?arrow_forwardTCP sessions are full-duplex, which means that data can be sent in either direction during the lifetime of the session. Consider a session in which the connection is established, the client sends 100 data segments, all of them are ACKed, and all of the ACKS are received by the sender, then the session is ended by both sides closing the connect. How many segments in total have the SYN bit of the header set to 1? а. 4 O b. 2 с. O d. 1 е. 209arrow_forward
- Consider a TCP session between Hosts A and B. Assuming that Host A sends a 10byte segment with sequence number 5, what will be the sequence number of the acknowledgment sent from B to Aarrow_forwardDNS makes use of UDP rather than TCP. If a DNS packet is dropped, there is no way to recover automatically. Is this a problem, and if so, how does one go about resolving it?arrow_forwardThree-way handshake is used by a TCP client and a TCP server to establish a connection, as illustrated below: 1st: client:port1 -> server:port2, SYN 2nd: server:port2 -> client:port1, SYNACK 3rd: client:port1 -> server:port2, ACK When this client is performing scanning attacks, it will generated a large number of failed connections. In each failed connection, the three-way handshake fails to complete. People commonly use SYN together with the absence of its corresponding SYNACK in this same TCP session to identify whether this connection is failed. By investigating the failed connections, an engineer finds that in legitimate/benign cases, if the server does not return SYNACK to the client, the client will not send the ACK packet after SYNACK (e.g., the 3rd packet above). Therefore, this engineer suggests that we can count the failed connections based on the following rules without considering SYNACK:arrow_forward
- TCP sessions are full-duplex, which means that data can be sent in either direction during the lifetime of the session. Consider a session in which the connection is established, the client sends 100 data segments, all of them are ACKed, and all of the ACKS are received by the sender, then the session is ended by both sides closing the connect. How many segments in total have the SYN bit of the header set to 1? а. 209 O b. 2 6 с. d. 4 О е. 1arrow_forwardConsider a client connecting to a web server via a router as shown in Fig.Q2. Client A sends a request to the server to retrieve a 7.5 Mbytes file. Given that the segment size is 50 Kbytes, the round trip time (RTT) between the server and client is 10 ms, the initial slow-start threshold is 16 and the client's buffer always has a storage space of 1 Mbytes. Assume that TCP Reno is used, there is no loss during transmission and the headers of protocols are ignored. 400 Mbps 200 Mbps 400 Mbps Link a Link b Link c Client Web Server Fig.Q2 (a) Describe how the value of sending window changes as a function of time (in units of RTT) during the whole connection time. 2.arrow_forwardThree-way handshake is used by a TCP client and a TCP server to establish a connection, as illustrated below: 1st: client:port1 -> server:port2, SYN 2nd: server:port2 -> client:port1, SYNACK 3rd: client:port1 -> server:port2, ACK When this client is performing scanning attacks, it will generated a large number of failed connections. In each failed connection, the three-way handshake fails to complete. People commonly use SYN together with the absence of its corresponding SYNACK in this same TCP session to identify whether this connection is failed. By investigating the failed connections, an engineer finds that in legitimate/benign cases, if the server does not return SYNACK to the client, the client will not send the ACK packet after SYNACK (e.g., the 3rd packet above). Therefore, this engineer suggests that we can count the failed connections based on the following rules without considering SYNACK: If a client:port1 sends…arrow_forward
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