[zeromq-dev] EPGM Congestion Control

Michael Holm Michael.Holm at tibra.com
Fri May 13 15:32:33 CEST 2011

2.  Correct me if I am wrong but I thought EPGM was PGM implemented over UDP. If this is correct then after you create the datagram socket you can set the option IP_MULTICAST_TTL via setsockopt. I do not believe this is currently available in 0MQ. Is that correct?

3. Yes, I could provide a patch. I plan on using 0MQ to distribute multiple prices feeds. It's not realistic to batch prices until you have a full UDP packet before sending them. This would add latency where it's not desired. I am assuming there is a timer tied to the queue which is performing this limit. Is that timer configurable and what is the default time interval?

"There is no actual question about PGM congestion control?" - (1) Nagel addresses from a TCP/IP POV. (3) Addresses it from an EPGM POV


From: Steven McCoy [mailto:steven.mccoy at miru.hk]
Sent: 13 May 2011 13:06
To: ZeroMQ development list
Cc: Michael Holm
Subject: Re: [zeromq-dev] EPGM Congestion Control

On 13 May 2011 19:15, Martin Sustrik <sustrik at 250bpm.com<mailto:sustrik at 250bpm.com>> wrote:
> 2.The EPGM interface does not allow you to set the time-to-live option
> in the setsockopt method.
There are no TTLs either in PGM or 0MQ. Do you mean IP TTL option?

That's what I would guess, IPv4 TTL / IPv6 hop limit.

> 3.When testing EPGM for throughput limits I discovered that all of the
> messages are batched until a UDP packet is full before sending it. I do
> not what this to occur. I want all messages to be sent as individual UDP
> packets. There should be an option to configure this functionality.
Sounds doable. Would you like to provide a patch?

This is odd, for throughput you generally want less packets as current day technology cannot saturate Ethernet with very small packets.

There is no actual question about PGM congestion control?


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