[zeromq-dev] PGM at high throughput

Steven McCoy steven.mccoy at miru.hk
Thu Jul 23 04:29:53 CEST 2009

2009/7/22 Robin Weisberg <robin.weisberg at gmail.com>

> ** (process:3895): WARNING **: dropped 203 messages due to invalid NLA.
> whats an NLA? What would cause this?

Hi Robin,

  NLA is the Network Layer Address, usually either a IPv4 or IPv6 address.
 In PGM this warning means that the recipient has not yet seen the NLA of
the sender and so cannot request retransmissions of dropped packets.

When a sender starts a session it sends three broadcasts of it's address,
then periodically every 30 seconds or 100 ms after a burst of data, doubling
in interval up to 30 seconds.  Also, when a recipient starts listening to a
sender who is already running it can send a request for the senders NLA.

This warning would likely appear when you have a network issue with traffic
not routing both directions, or too high load on the sender as it is not
responding to requests for it's NLA.

The multicast test tools from 29West are high recommended to diagnose any
routing issues on your network:


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