Multicast traffic % in enterprise network ?

Brian Knight ml at knight-networks.com
Thu Aug 9 04:26:29 UTC 2018


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


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,

-Brian


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