On 2018-08-08 13:49, Mankamana Mishra (mankamis) via NANOG wrote:
Hi Every one,
Recently we had good discussion over multicast uses in public
internet. From discussion, it was pointed out uses of multicast is
more with in enterprise.  Wanted to understand how much % multicast
traffic present in network

  *   If there is any data which can provide what % of traffic is
multicast traffic. And if multicast is removed, how much unicast
traffic it would add up?
  *   Since this forum has people from deployment area, I would love
to know if there is real deployment problems or its pain to deploy

These questions is to work / discussion in IETF to see what is pain
points for multicast, and how can we simplify it.


Hi Mankamana,

I once worked for a financial futures broker-dealer where I implemented multicast, which was around 2009. They had one main application, which was a trading "screen" that traders and customers used to execute trades. I would guesstimate maybe 5-10% of the packets and bytes flowing over the network was multicast, depending on network conditions.

In terms of bandwidth savings, I'm not sure how much we saved. We had nine or ten participants using that particular application. However, they all worked on different desks, trading different products. The app was smart enough to send only the price feeds in which the user was interested. Assuming at least 50% of the users looked at the same price feeds 50% of the time, I'd say it saved about 25-50 meg.

We also had one major exchange distributing price feeds via multicast. However, that feed was not routed on our network. Our systems plugged directly into exchange-provided switches for the feed.

The hurdles I had to overcome to implement multicast were:

* The learning curve for PIM. Deciding on the deployment model was difficult, as were the first few support calls. We wound up going with PIM-SM w/ BSR for RP selection.

* Vendor support for PIM on our gear. These were mainly troubles with PIM running on firewalls in high-availability mode.

If I had to do it over again, I wouldn't have bothered with multicast. It was a great opportunity and we learned a lot, but the app had a unicast mode of operation that would have worked perfectly fine for our purposes.

I work for an ISP now. We have decided not to support multicast on our network for now mainly because of the learning curve, and also because we simply don't see that much demand. Those two or three prospective customers that wanted it, wanted it for multi-site video conferencing on an MPLS VPN.

Hope this helps,


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