Link Layer Topology Discovery

Question

Im New to wireshark and new to networking. Im trying to solve a issue with our phones, everyday at 5:30pm our phones loose connection. While exploring wireshark I found my first error and was hoping someone here can explain to me what I am reading

It seems like for my Netgear switch there is a Link Layer Topology Discovery error, or its highlighted in red. Under that TLVs than TLV ITem (Friendly Name) than finally this error.

[Expert Info (Error/Malformed) : Invalid Friendly Name length] screen shot Any Help explaining what this is?

Answer 1

This looks like some incomplete work in the dissector or maybe a different implementation of the LLTP protocol. In the source code of the dissector I find:

case 0x11: /* Friendly Name */
    if (length != 0)
        expert_add_info_format(pinfo, tlv_item, &ei_lltd_tlv_length_invalid, "Invalid Friendly Name length");
    break;

Which means, the length of the Friendly Name should be 0, which kind of contradicts the reason for having a Friendly Name TLV. My best guess is that this field was not used in the test data that was used to create the dissector but is indeed used by your netgear device. Could you add a bug-report to https://bugs.wireshark.org and attach a little tracefile with this packet in it to the bug-report?

Unfortunately, I'm afraid this brings you no closer to finding the source of your VoIP problems...