Multicasting and the Small Network - Part 1

With the growth of IPTV and other IP media streaming technologies, applications for multicast technology are increasing. Live Video broadcasts and VoIP applications are viable uses for real time transmissions over an IP network from a single source to multiple recipients.

Most data transmissions are unicasts, which are a one-to-one data stream sent from one device to another device. Email, web surfing, and file downloads are all examples of unicasts, even for the busiest sites or most downloaded files. Although a single web page may be visited thousands of times each day, each time it is viewed it is individually transmitted to the requestor's PC as a unicast.

Packet Capture to the Rescue

In my last two posts on this subject, I've covered some of the basics and tools used to perform packet captures, highlighting the well known software from Wireshark. In this installment, I'm going to show how I used Wireshark packet captures to solve a real network problem.

Packet Captures and Network Devices

Using packet papture software like Wireshark is a useful troubleshooting technique that can be used to examine packets and gather details to help find the root of a problem. In my previous post, I talked a little bit about how to use Wireshark and walked through some steps to run a simple packet capture from a PC. This time, I'm going to go a bit deeper into the how to for doing packet captures.

Packet Captures, Plain and Simple

One of the features I've seen in newer small network routers is the inclusion of a packet sniffer/capture/trace tool within the diagnostic menus of the device. Routers I've recently tested with this functionality include the SonicWall TZ190W, D-Link DFLCPG310, and Netgear's newly released FVX538 and FVS336G.

In each case, these devices have the ability to capture packets on a specific WAN port and/or on the LAN interface. Some of these routers have more sophisticated filtering capabilities than the other, but they all seem to have the same basic functionality of capturing packets.