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2
votes
1answer
410 views

OpenVPN: How to mitigate path MTU issues on a per-client basis?

We have dozens of embedded devices installed at customers, all calling home to our OpenVPN service. That works fine in general, but a few of our customers have severe path MTU issues. Our influence on ...
0
votes
0answers
76 views

Can a source send two fragmented IP packets at the same time?

I'm developing an app that does NAT between a virtual TAP interface and a physical interface, and I'm not sure how much buffer should I allocate for IP fragmentation. According to Wikipedia the ...
7
votes
1answer
1k views

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?
6
votes
1answer
1k views

Why is iptables rejecting the second and subsequent fragments of an allowed packet?

I have two hosts which are attempting to set up an IPSec connection with each other. For this they have to communicate on UDP ports 500 and 4500, so I opened them in the firewalls on both ends (shown ...
3
votes
1answer
673 views

Does Windows XP automatically reassemble UDP fragments?

I've got a Windows application that receives and processes XML messages transmitted via UDP. The application collects the data using Windows "raw" sockets, so the entire layer 3 packet is visible. ...
2
votes
1answer
242 views

Matching last fragment of IP packets using tc or ipfilter

I am transmitting UDP packets of say 2900 bytes. Due to fragmentation, packet is divided in 2 IP fragments. My tc u32 filter (more fragments bit and IP/PORT combination) matches only first fragment ...
3
votes
1answer
77 views

IP segmentation occouring at irregular boundaries

I have an IP packet of header length of 20 Bytes and data length of 4096 Bytes. The maximum transfer unit of the network is only 1500 Bytes. As I understand fragmentation, the fragmented packet will ...
2
votes
1answer
99 views

seeing remote MTUs of 250 and 68. is this ever valid?

I'm seeing an ICMP storm from a mobile phone netblocks belonging to "TELEFONICA MOVILES". Periodically we will get upwards of 5 million in a few seconds, all something like this: 08:12:05.740781 IP ...
1
vote
3answers
851 views

Implementing IP fragmentation

I'm working on an application that does network traffic generation. The application has eth1 in promiscous mode. So it directly handles all incoming and outgoing traffic. One of the features I'm ...