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Questions tagged [packet]

97 questions
65
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2 answers

iptables: difference between NEW, ESTABLISHED and RELATED packets

Part of a firewall on a server : iptables -A INPUT -p tcp --dport 22 -m state NEW --state -m recent --set iptables -A INPUT -p tcp --dport 22 -m state --state NEW -m recent --update --seconds 100 --hitcount 10 -j DROP When I search online I always…
Kris
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38
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5 answers

How do you diagnose packet loss?

I realise this is very subjective and dependent on a number of variables, but I'm wondering what steps most folks go through when they need to diagnose packet loss on a given system?
KushalP
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14
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1 answer

Why is the "don't fragment" flag set in https and ssh protocols?

I've found a lot of information specifying that this is the case, however, I am really looking for the reason behind this. Why is it necessary? Is it necessary?
Aiden Thompson
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8
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3 answers

Excessive 'TCP Dup ACK' & 'TCP Fast Retransmission' causing issues on network. What's causing this?

I'm getting excessive TCP Dup ACK and TCP Fast Retransmission on our network when I transfer files over the MetroEthernet link. The two sites are connected by one sonicwall router, so the sites are only one hop away. Here is a screenshot from…
Ingram
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6
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1 answer

Outbound Packets Dropping / Timeouts - Only with Azure

I have an issue with packets dropping to a third party data center in Florida, USA. The issue only occurs on Azure Virtual Machines, no matter which data center the VM is in. I've done the same tests simultaneously from other non-Azure networks,…
Andrew Bucklin
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6
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1 answer

iptables drop packet by hex string match

I got this packet captured with tcpdump but I'm not sure how to use the --hex-string param to match the packet. Can someone show me how to do it? 11:18:26.614537 IP (tos 0x0, ttl 17, id 19245, offset 0, flags [DF], proto UDP (17), length 37) …
Flint
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5
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2 answers

Configuring Frame Relay using a Switch Simulation - Packet Tracer

I have the following set up in Packet Tracer: I am trying to configure frame-relay between the RTR-EDGE router, the RTR_ENG router and the RTR_SAL router using a frame-relay switch simulation (the cloud). I have used the following…
DJDMorrison
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5
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2 answers

Can 3G networks be packet sniffed / analyzed?

Just wondering if 3G networks can be sniffed like public wifi networks, via wireshark for example (I'm almost sure this is not possible due to encryption, but I just want to make sure?)
foreyez
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5
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2 answers

How is packet collision avoided in full duplex mode?

While working in full duplex mode, one can send and receive packets simultaneously. Why don't the packets collide?
user51911
4
votes
1 answer

Linux bridge (brctl) is dropping packets

I have been researching this problem for a few days and have not found an answer yet. Your help will be really appreciated! I have a few VMs (Virtual Machines) running on a physical server. The server uses Linux bridge (br100) to connect these VMs…
Kenneth
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4
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1 answer

TCP sequence number and ACK number

Is the TCP sequence number just the ACK number + bytes received? Is it different when doing the 3-way handshake?
Wintermute
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3
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4 answers

Smaller network packets vs bigger packets - confused

Some are saying that bigger packets are better to send then smaller. But in this app: http://media.pearsoncmg.com/aw/aw_kurose_network_2/applets/message/messagesegmentation.html The lower the packet size is, the smaller amount of time it needs to…
exeq
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3
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1 answer

Packet loss during TCP handshake

I have to implement a pseudo TCP handshake that leads into a file transfer. I have no problem doing the file transfer: simple send-acknowledge. What I can't wrap my head around is how to do the three way handshake assuming there will be packet loss…
user111658
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3
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1 answer

Confusion about TCP packet analysis terms

I'm analyzing our network and have some confusion about the terms: this is the 2-packet output from source to destination. from these i have to get some features as describe, pls make me clear... packets with at least a bytes of TCP data payload:…
Berkay
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2
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0 answers

FreeBSD: redirect some UDP traffic from one port to another

I have some specialized DNS servers running on FreeBSD 11. A few people keep hammering on them and I would like to give them different answers. So I'd like to divert UDP traffic from those hosts from port 53 to port 5300 where a different server is…
John Levine
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