TCP/IP Subnetting

[Samer Shami]

The TCP/IP protocol has the ability to broadcast a packet to all computers in certain cases. In order to prevent this broadcast from flooding the whole network subnets were created. Subnets simply limit the number of addresses that can natively talk to each other and hence receive the same broadcast address. To enable computers to talk to each other between different subnets a router is required.

The reality is that different subnets can happily co-exist on the same physical cable. Under normal circumstances PCs on subnet A will never see data destined for PCs on subnet B even if they run over the same cable. It is a routers job to shunt relevant data from subnet A to subnet B.

How does this relate to Control4?

It means that if you wish to segregate Control4 traffic away from regular PC traffic you simply need to place it on a different subnet. So how do you give the MC or HTC the ability to access the ‘Net or give yourself/client the ability to access them from the PC network?

My recommendation is to use a PC as a router. The PC doesn’t need to be anything special to function within this role. Pentium II with 64MB of RAM is more than enough. Make sure it has two network cards and no hard drive.

Then go and download the m0n0wall (www.m0n0.ch/wall/) firewall software. Get the CD-ROM image version (don’t worry – it is only a 6MB download!). This version operates entirely off the CD-ROM and saves all settings to a floppy. Using this software you can easily define different subnets on the two network cards and also define rules that will allow routing between the two subnets. This software is also very flexible in its DHCP options. It can even give static DHCP addresses! If a particular MAC addresses requests an IP address, you can give it exactly the same IP address every time. This is like combining the best of static IPs with the best of dynamic IPs.

If I get enough interest from people, I will post a few screenshots to guide you through the setup procedures.

[Taylor]

That actuallysounds pretty cool. However, as to dedicating a computer of a clients to do that is iffy. I want to try it though, on my "server" computer. Sounds pretty sweet, I'll take al ook at it!

[Kirill]

I suggest you buy a switch for 50$ and let it deal with directing packets

[yellowdog]

The trouble is a switcher does not rewrite the addresses like a router. A router stores and forwards with its own address in the "from" field. A switcher does not modify the packets - just retimes and switches to the appropriate output based on its CAM table. Layer 3 switching deals with IP addresses, layer 2 switching deals only with MAC addresses. SO you can't bridge subnets with a switch.

[chambrick]

...plus I don't think there is any significant advantage to creating different subnets just for C4 stuff.

[slemay]

I suggest you buy a switch for 50$ and let it deal with directing packets

A switch will still do a broadcast, which is about 1/8 of the traffic on the net (everytime someone asks for an address .... ie: DHCP ... that's 4 broadcast announcements that every device on the LAN hears... just as one example). A Router, or LAYER3 switch with different subnets will isolate that traffic and keep it off each others networks. Not to mention, when you start dealing with wireless - this will be a HUGE problem (no so much with the LAN traffic). A wireless device acts as a HUB - which means BEST CONDITIONS you can never expect more then 30% of what it's rated at (ie: 54mb 802.11g will REALLY only give out 16.2mb - and that's with only ONE device on the WAN (Wireless Access Network). Why do you think C4 last week stated, don't try and put wireless to more then 3-5 streams MAX - they did the math!!!!

I've posted about this already in other forums - but Samer Shami is hitting it on the head - subnet and route between the two if you must - but keep the two seperate at all costs - it'll save yourself from headaches down the road! Remember - we're already the least expensive solution out there - adding a dedicated switch and WAP won't make you more then the next guy - you'll STILL be the least expensive!

[Samer Shami]

Kirill I think had you made the statement: "I suggest you buy a router for 50$ and let it deal with directing packets" I would have agreed 100%.

The method (using m0n0wall) that I described is more complex than it may need to be. Granted if you were to buy a cheap router and connect all C4 equipment to the LAN ports and connect the router's WAN port the client's regular network you should be able to achieve what I spoke of. This would segregate the Control4 equipment while still allowing the HTC/MC to access the Internet. One caveat (or more a personal preference): I generally think the DHCP software stacks on PC based firewalls are more solid and reliable than those on cheap routers.

chambrick: There is no direct advantage of subnetting as you say. I was advocating having a different DHCP server for the Control4 equipment by means of subnetting. slemay also made a valid point that going a little further and completely segregating Control4 traffic to different physical cables from the regular LAN traffic would be of benefit.

My initial motivation for starting this was because hgrace expressed concerns regarding DHCP addresses with the mini-touchs. I thought this solution might be a way to rectify it.

[mfjv4]

I've asked myself whether subnetting is necessary and have come to the belief that it is not if you can manage and insure the LAN wiring are home runs to a central location.

The fundamental approach is to 'segregation' the traffic into affinity groups where the transiting of one groups traffic across another's is minimized. That is, if you look at the VoIP traffic in a home or business, it will have no interest in communicating with any C4, PC, video server or music server devices. It's only interest is to go out to the Internet. VoIP traffic can withstand some packet loss but not delays, so you must place the VoIP gateway/voice adaptors immediately after the broadband firewall /router. This allows that VoIP adaptor/router to prioritize traffice and ensure voice integrity.

The next affinitiy group are your home/business PCs (I've got 10 in my home). Like the voice traffic, the majority of my PC traffic seeks the Internet, not the C4/music/video server gear. So I place my PCs on a LAN switch immediately behind the VoIP adapter/router. The PCs are happy because file sharing easily takes place without interfering with the VoIP traffic and not imposing any traffic loads across C4 devices.

Lastly, I plug another LAN switch (today 100 Mbps, tomorrow 1 Gbps when video servers will be used) into the downstream side of the PC LAN switch. Into this LAN switch I connect all the C4 gear (controllers, speaker points, M/T, etc) AND my NFS music server. The traffic from this affinity group tends to want to stay in its own little corner of the LAN segment. The few times members of this group seek the Internet is to perform firmware updates, to get cover art and for remtoe access. Otherwise, the heavy streaming (today audio tomorrow video) stays within the second LAN switch.

With this arrangment I see:

1. LAN switches are cheap, cheap, cheap

2. Packets of C4 matter predominantly stay within this LAN 'cul de sac' and do not interfere with voice or home PC traffic

3. Problems that home/business owners see on their VoIP and PC services for which they blame on C4 networking can be easily dismissed by disconnecting the C4 LAN switch from the PC LAN switch

4. Reachabilty among all devices is ensured since they are all on the same subnet

5. Future upgrades to high bandwidth, namely Gig E are easy (providing you planned CAT6 for the cul de sac LAN segment) by just upgrading equpment

The gotcha that I see is... when source media is no longer originating from within the cul de sac, i.e. from the NFS' located within the local LAN segment, then you'll have the devices in the cul de sac tramping all over the PC traffic (the VoIP will always be protected by the policing that's taking place at the VoIP terminal adapter). If/when that happens, I'll have to use the last router (i.e. the one that is deepest into the house/business to split it's LAN ports into subnets and insert a fixed routing plan.

Today, in my home I have

Broadband cable modem --> Linksys Firewall Router --> Bradband Router with Voice lines --> Wireless G Router --...

... --> 100 Mbps LAN switch 12 port feeding my network printers and PCs --> 10/100/1000 LAN switch 5 ports feeding DLINK

NFS (hosting a 400GB Hard Drive containing 1200 CDs over 5000+ tracks of music) and my C4 devices.

Everything is working great from a networking/traffic perspective .. my only problems are with C4 instabilities and lock ups of the M/T and Zigbee remotes from time to time. I use HTCs only in this config.

Hope this offers an alternative to the discussion of subnets. .. marcel

[BaZa]

The lack of speed is due more to software issues and memory than internet speed itself. I would bet that most of the mini-touch screens out there are not used for streaming audio either. The speed will get better as they upgrade their processor speeds as well as flash memory and other internal things. You can make minor dents in performance with a small amount of things you can personally do, but for the most part, you get what you get.