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Questions tagged [icmp]

For questions about the Internet Control Message protocol.

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17
votes
2answers
29k views

Traceroute - every packet has TTL == 1

I'm working on Wireshark lab-IP in Computer networking - A top down approach and I don't understand why every packet that normally expired has a TTL of 1. Here is my Wireshark capture file. https://...
7
votes
5answers
3k views

Why is the ICMP protocol considered to run at layer 3 on the Wikipedia page?

Why is the ICMP protocol considered to run at layer 3 on the Wikipedia page (same layer as IP) when the ICMP protocol data is a payload of the IP packet? This is the article on Wikipedia that states ...
5
votes
3answers
2k views

Does a router send frames or packets?

Perhaps it's a novice question, but does a router send/receive frames? When I read about this subject, it seems that routers decapsulate the frame on arrival, and encapsulate the packet in a frame in ...
1
vote
2answers
302 views

Decrease the Router's buffer size

Through this topology, I want to decrease the buffer size of R2 in order to generate an ICMP Source Quench Message, but I have no idea how to do it. I'm open to other suggestions to generate a Source ...
4
votes
3answers
4k views

Telnet - “Destination unreachable” response

I'm looking to implement, what I feel, is Telnet security when it comes to unwanted hosts initiating a Telnet connection to one of my devices. I can lock down a specific subnet or only allow a range ...
9
votes
3answers
18k views

Traceroute Over TCP vs UDP

For what purpose would one wish to send traceroute over TCP rather than UDP? What advantages/disadvantages are there in doing so? I know that traceroute normally uses UDP ICMP "echo" packets while ...
3
votes
2answers
262 views

Confusion about MTU

I am studying about IP fragmentation and MTU. What I know is MTU is the property of Physical medium, as in the amount of data it can process without having to fragment the data. The default MTU on ...
1
vote
2answers
94 views

why ICMP Time Exceeded packet takes longer ICMP Echo Reply

I've noticed that when I use tracert a certain router(hop) always takes about 200ms to reply back, the rest reply's in 50ms, after digging into it with wireshark I've noticed that tracert uses normal ...
1
vote
1answer
55 views

How to prioritize ICMP time exceeded packets

According to why ICMP Time Exceeded packet takes longer ICMP Echo Reply, it is normal for ICMP time exceeded be treated as low priority and slowed down or even discarded. I'm observing this problem ...