Wireshark

How to take a network capture using Wireshark

Wireshark is a free and open source packet analyzer that can be used to look at DDS traffic when debugging an issue. Sometimes RTI’s Support team will ask for a network capture when working to resolve an issue reported by a customer. While we have a more comprehensive Using Wireshark with RTI ...
hainsworth
Wed, 04/24/2024 - 13:33
1660 reads — 0 comments

How to uniquely identify a coherent set

Note : This article discusses the coherent_set_info field, which is only available in Connext Professional 6.1.0 and higher. The information about the coherent set that a sample belongs to is stored in the optional field coherent_set_info , which is part of the SampleInfo structure. This optional ...
plombardero
Tue, 05/10/2022 - 09:35
1806 reads — 0 comments

Under which circumstances will Connext DDS send non-user data?

When we call DataWriter::write() , we expect to see a user data packet sent on the wire, but under what conditions will Connext DDS send packets of its own accord? There are many reasons why Connext DDS may send messages other than user data. Some of the more common reasons are described below. ...
samr
Mon, 03/04/2019 - 05:48
4872 reads — 0 comments

What are preemptive ACKNACK and preemptive heartbeat messages?

The DDS reliability protocol uses Heartbeat messages and ACKNACK messages to ensure the receipt of data. A DataReader sends an ACKNACK message in response to a DataWriter’s Heartbeat; this ACKNACK message indicates which samples the reader received, and which samples it has yet to receive. For ...
grayson
Mon, 01/07/2019 - 15:22
6941 reads — 0 comments

How to capture traffic if my Connext DDS applications are communicating through shared memory

Wireshark and tcpdump are very powerful tools which you can use to capture traffic. They may come in handy when debugging issues with your DDS applications. These tools can capture all kinds of packets: RTPS, UDP, TCP, IP… However, they cannot capture traffic if your applications are communicating ...
Francisco Porcel
Fri, 07/28/2017 - 07:38
44951 reads — 0 comments

Configuring DDS to mitigate performance degradation due to packet loss

If you are using Reliable communication, you could see a performance degradation due to packet loss and resending data sample fragments. This is more probable when using data bigger than 1500 Bytes (over Ethernet). In general, a DDS application using a transport such as UDPv4 splits data samples ...
sara
Wed, 07/19/2017 - 02:29
7228 reads — 0 comments

I am not receiving samples, could it be IP fragmentation?

What is IP fragmentation? IP Fragmentation occurs when the payload provided from the transport layer (typically UDP or TCP) exceeds the maximum payload that fits in a single Ethernet Frame (a.k.a. MTU). When the receiver NIC gets IP fragments, it stores them in a buffer until all the fragments are ...
Francisco Porcel
Wed, 07/05/2017 - 07:05
14005 reads — 0 comments
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