We are planning the networking for our new place. It will be all GHz CAT6, with a couple of 48-port switches. We'll be going VOIP for the telephones, which means that each rented phone just plugs into the nearest ethernet switch.
Our IP consultants want a separate network and separate switches for the phones, their concern being that data traffic could make the phones strutter. We don't have gigantic data traffic, and ethernet is supposed to manage traffic anyhow, so I think the concern is overblown.
If we buy the expensive smart/managed switches, which they also want us to do, we can also throttle various ports if we do have problems.
I think the consultants are a bit over-the-top. They would probably install the gear and wiring and manage the smart switches, so their incentives are not my incentives.
They also don't like microwave internet access, but a MonkeyBrains dish on the roof would be a heap cheaper than digging up the sidewalk for fiber or whatever. The microwave hop would be two blocks with a
173 dB link budget.
Any experience with running data and voice over the same network? Any advice?
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John Larkin Highland Technology, Inc
lunatic fringe electronics
We have 2 VOIP remote phones running over RV042's. The RV042 is also the gateway for the shop. 100/30 cable plan. For these two phones with both callers yakking it should be 160kpbs. Other than client side problems I don't see any problems, but the port is prioritized so the packets get thru.
How many lines? the managed switches would be the way to go. Networks performance is much better with that type of hardware.
That microwave hop should work provided the underlying infrastructure has enough bandwidth even when lots of customers stream some ballgame. The path should also be unobstructable. All it takes is a glitter-colored sales event ballon in the air and it's all over. Though silence on the network can have a soothing effect on modern mankind. When the Internet went down for four days a while ago it wasn't all bad. No more looking up web cheat sheets for calcs, had to use a book.
I have no personal experience but clients who switched to VoIP without a
2nd network. "Please say again?" ... "The pler section kage" ... "Say what?" ... "Oh, yeah, we just switched to VoIP, let me call you from my cell".
Get a quote from your IP consultants for what the consultants want , and al so what you think is adequate and a quote for changing what you think is ad equate to what the consultants want. If the quotes are reasonable you can start with what you think is adequate and if necessary go to what the con sultants recommend. Yeah it might cost more, but could also cost less.
Normally VoIP is implemented on a separate VLAN on the switches (there are protocols to have the phones jump to the correct VLAN automatically so it causes no setup nightmare) and this VLAN is tagged with a higher priority than the base DATA VLAN. Then there is no issue when the DATA network is saturated, as the voice traffic goes first.
This is possible with all but the most basic switches, don't let them claim you need expensive Cisco switches for it.
Good. I suggest you consider fiber for any high traffic internal backbones, such was the machine that's doing workstation (image) backups.
Duz a "couple" mean two? A few problems here. Make sure they're "managed" switches, which is IT talk for supports SNMP. Troubleshooting switch problems without traffic and error data via SNMP is a PITA.
48 ports is a good number depending on your undisclosed number of client machines, printers, gizmos, gadgets, test equipment, and such that require ethernet ports. I usually recommend at least twice the number of ports per switch (and per room) as there are devices that can be identified when the system is planned. I'm usually close.
Ethernet switches with lots of ports is the ultimate single point of failure. Everything goes through the switch. If the switch goes up in smog, your entire network and everything plugged into it are dead in the water. From my warped perspective, that means you buy the best, monitor performance, and have spares on hand. Be prepared to abandon blown ports. For Cisco, have spare replacement power supplies handy.
Unfortunately, my customers are cheap, so I have a few old 10/100 switches with 8 to 48 ports handy which allows my to throw something together until the big switch can be replaced. The problem with this is that if you setup a VLAN (virtual LAN) replacing the big switch with lesser devices isn't going to work well. That's one reason for SDN (Software Defined Networks): You're not big enough to need or want such a thing (and the IT staff that comes with it) but you should be aware of the technology.
Make sure your ethernet switch provides PoE (Power over Ethernet) or you will have a tangle of AC adapters everywhere. Well, you'll probably have such a tangle anyway as they're hard to avoid, but PoE will eliminate at least one wall wart per desk. Also, do the math an add up the power consumption of the phones and make sure that the total PoE power provide by the switch is adequate. While most switches have PoE on all ports, they may not have enough power to drive all the ports at the same time. Also, some switches are rated for only powering half the ports.
Not always. Add up your VoIP network traffic and you'll find that it's trivial compared to the available gigabit bandwidth. What causes the VoIP garble are applications that are capable of sucking ALL of that available bandwidth, leaving nothing for VoIP. If you are hearing garble, you're LAN is dropping UDP VoIP packets probably due to congestion. You have a few options here for managing your bandwidth:
Separate LAN switches and separate wiring for each network. That doubles your wiring in the walls, doubles the network cost, and does nothing to protect the network from the real bandwidth hogs (video and backups). Are you also going to install a separate LAN for video and backups?
VLAN (Virtual local area network). This allows you to break your network apart into several segments, and assign each ethernet port to one of the networks. In simulates having multiple switches. To avoid having to run two cables to each desk (one for data and one for VoIP), there's 802.1Q packet tagging, which designates the target VLAN.
Brouter (bridge-router). Switches work on the MAC address layer (layer 2). Bridges add the IP layer (layer 3). Layer 3 switching allows you to introduce QoS (quality of service). QoS is simply a filtering service that reserves some bandwidth for time critical services at the expense of less time critical services. It's quite common in home routers to deal with SIP (VoIP) phones and limited internet bandwidth. You won't like the prices on the brouters.
You're probably going to have the biggest problem with traffic contention in your internet router. You may have gigabit bandwidth on your LAN, but you probably don't have anywhere near that much on your internet connection. Make sure you enable and configure QoS to give preferential treatment to SIP (VoIP) packets.
What's nice about ethernet is that traffic between two ports does NOT affect traffic between two other ports. That means you can run gigabit high bandwidth backups between two ports, and talk with VoIP between two other ports without the high bandwidth traffic affecting the VoIP in any way. Well, almost any way. The switch has a maximum internal backplane bandwidth which cannot be exceeded. For high end Cisco switches, it's in tens of gigabits/sec or more. For low end cheap gigabit switches, it can be as low as 2 gigabits/sec.
The backbone bandwidth is also where having two or more ethernet switches. If the switches are sitting on top of each other, there are two expansion ports and interconnecting cable for expanding a switch without any loss of bandwidth. However, if the two switches are located in different parts of the building and connected with a single CAT6 cable, traffic between the two switches is limited to 1 or 2 Gbit/sec. In effect, this reduces the 10+ gigabit/sec backplane bandwidth to 1 or 2 gigabits/sec (unless you get switches with 10G fiber ethernet ports).
I've done quite well helping customers who made similar assumptions get their VoIP running. I don't believe anyone's data traffic numbers until I've sniffed and measured their traffic. You're probably right about the average traffic, but I don't think you're considering your peak traffic. Gigabit networks offer considerably faster response times. When I upgrade networks to gigabit (usually by just replacing the 10/100 switches with gigabit and leaving the CAT5e alone), everything seems to go faster. The programs aren't running much faster, but the response time to anything requiring server access is much faster. Individually, it's probably only about 100 msec per keystroke or mouse click, but multiplied by the number of keystrokes a person does on a typical day, the effect is substantial.
Ethernet (Layer 2) doesn't really manage traffic. It uses a CSMA/CD algorithm to deal with collisions and juggles packets sizes. Retransmissions and error control are handled by TCP/IP on Layer 3. The CSMA/CD algorithm breaks down when the network segment is near maximum capacity, which is quite common with todays bloated software and bursty traffic application. You can count on ethernet to do its job at low or moderate traffic levels, but not so much at high levels.
Sure. A VoIP phone doesn't require any more than 10 mbit/sec port. However, once that packet gets into the switch, it's competing with high traffic programs for access to a server or router. Unless the switch has some means of prioritization, there is going to be some contention. To be fair, you're probably ok with todays applications. I'm not so sure about tomorrows apps.
Yep, that's about it. Your IT people are covering their posterior by overdesigning your system. I would do the same. I don't like working right on the edge of a capacity limit. Running out of ports, failure to disclose badly behaving applications, and devices that nobody mentioned are common. Never mind rogue access points, malware, and spam servers. I try to plan for at least 1 year's worth of capacity expansion. Planning only for tomorrow is a bit tight for me.
I would be more interested in the fade margin. Gigabit wireless ethernet is quite common these daze. I've only done one 60 Ghz link. I had a hell of time getting the dishes aligned and then keeping them aligned after I discovered that rooftop shelter moved when the elevator reached the top floor. Oxygen absorption was not a problem and actually advantage in that it attenuated interference from other rooftop 60GHz links. Of course, the chose line of sight pointed almost directly at another 60GHz antenna. Heavy rain was a problem, but worked ok in light rain or fog. There were some outages, which I like to attribute to birds, but I'm not sure. Most of the downtime was caused by people working on the rooftops, such as HVAC and cellular antenna.
Sure. It works as long as you can prevent applications from saturating backplanes, backbones, and network segments. Use G.711 (90kbits/sec0 uncompressed codec for intelligibility. There are VoIP bandwidth calculators available: Calculate your worst case bandwidth consumption assuming all the phones are in use simultaneously. You can simulate how it would work with your present ISP and connection at various VoIP test sites: Watch out for jitter and packet loss.
Drivel: Every time I move, it's either the hottest day of the year, or it's raining.
Good luck.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Ours are run over the same networks, sometimes computers being plugged into the phone's aux port, and everything works OK. I hate the phone system but the phone itself works fine. They're nice because they'll work anywhere on our network, even across town or in another state. ...not that we carry our phones with us.
Running VOIP over your internal network should be totally fine. it would be REAL hard to overload it to the point that the tiny VOIP traffic couldn't get through. But, I suppose if a couple powerful local nodes are sending giant files at the same time, it could use up the bandwidth, for instance, if they are all sending data between the two switches over a single link between them.
I have all my phones on a separate switch, because it is the only one with PoE.
At my day job (major university) they are going to put thousands of VOIP extensions on the main data network. I have no idea if this will cause problems. We DO have powerful nodes sending big files around, so it could be an issue.
Florida Spectrum internet don't expect reliable FAX service as such as down here so check your service agreement on that. Only two phones and one FAX when it feels like it.
Spectrum does not guarantee FAX through the VOIP service they use here.
Cisco voip telephones have pass-thru ports alloing them to be daisy-chained or to share an ethernet connection with another device.
Their ethernet is only 10/100 so gigabit switches are wasted on them
Their power-over-ethernet capability can be handy, but in the end it comes out about even, or slightly more expensive than using they're inconveniently shaped plug-packs to power each phone.
Had no problems running a plain SIP setup with an Asterisk PABX as controller. Cisco has their own controller too, if there's one on the LAN it will infect plain phones and take them over (or automatically configure them), a "factory reset" using the menu cures this.
One reason to separate the nets would be to use cheaper 10/100 switches to service the phones. Voice is less than 128 kilobit per seconds for a session, (usually signitifcantly less - like 9600kb/s ) so a 10 megabit channel can theoretically handle 80 sessions
Unless you're setting up a 1000 seat call-centre there's no reason to consider gigabit net for the phones.
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This email has not been checked by half-arsed antivirus software
Two should be enough for data and phones. We can add more if we need to. Little local switches or hubs might be needed, to avoid running extra home-runs to an office or the lab or something.
A few problems here. Make sure they're
What do you think of "smart switches" like this one?
formatting link
It looks like it does the same stuff as a managed switch, but has a web interface and doesn't seem to need additional, licensed software.
We'd have at least one full spare switch on hand. And one full server PC, ready to go.
We'll probably need PoE for phones. I want a camera system too, but that will probably be one central box with a (long!) run from the box to each camera, a separate system. When the alarm company calls me at
2AM to report motion, I don't want to go over there and meet the cops; I want to snoop the cameras, declare nothing wrong, and go back to sleep.
Right. Sounds like the Cisco smart switch can do that.
Sonic is now providing us 30 Mbit downloads and lucky to hit 1M upload, and that's sort of OK. We're considering MonkeyBrains at
100/100 or maybe 200/200 (guaranteed minimum!), or (gulp) Comcast. Comcast seems to get bimodal-distributed reviews, great and terrible.
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John Larkin Highland Technology, Inc
lunatic fringe electronics
Another nice switch for VoIP is the Netgear GS110TP. This has web managed gigabit switching (which is good when PCs are chained through the phone) 8 PoE ports, two SFP ports and most importantly is fanless. The SFP ports don't care what make of SFP module is fitted. It is also relatively inexpensive so it is easy to have a spare on site.
The main limitation is that the total power budget is 46W spread over the 8 PoE ports. Not a problem when powering phones until somebody decides to use the USB port on the phone as a charger. This works fine. Then a few more people think that is a good idea too and somebody completely different gets the power to their phone cut off by the switch's power management algorithm.
The other limitation is that it does not have a rack mounting kit.
I have no experience with that switch. I'm used to managing networks from a PC running some flavor of SNMP base management software, such as Nagios, OpenNMS, NMIS or just monitoring with MRTG and RRDtool. At first glance, it looks like the above switch replaces some of the management functions, but not the monitor functions, which I suspect you can live without. Give me a day or three to do some reading on the 200 series to see what it will do. I'll throw together a feature list of things that I would guess you'll need and see if the 200 series can do it. Meanwhile, I suggest you talk to someone more familiar with Cisco hardware (CCNP). I'm not very familiar with current Cisco hardware.
Yep. Also, a spare power supply.
Yep. If you're planning on using the pass through port on the VoIP phone, things can get complexicated. Most phones don't work with
1000baseT and the pass through "output" port does not have power needed to run downstream PoE devices.
Sigh. Don't forget about video conferencing and other bandwith hogs. One use that you'll probably find useful is plugging in a network camera in the lab so that you can watch some circuit bake, dry, or run in your office or at home. I made the mistake of setting up such a system for a customer, who now has far too many of those running on his network.
The problem is that video cameras default to using ALL (and I do mean ALL) the available bandwidth. If you plug it into a gigabit network, it will try to deliver 1080p video at its maximum frame rate. See: So, the cameras have to be properly configured. My preference is high resolution but slow frame rate. 1 frame per second is enough for a security camera when you can actually recognize the person breaking into your lab. Minimum would be 720p. If you're going to use wide viewing angle cameras, a persons face is going to be only a few dozen pixels wide. To be able to recognize someone on a camera, you need as many pixels as practical, or a narrow angle lens and more cameras. Incidentally, mount the cameras a little above eye level. Too high and you get a nice clear photo of the top of a persons head.
Yep. The joy of false alarms. In Santa Cruz, if the police show up for a false alarm, it's $75 and increases with every false alarm. See "False Alarm Cost" at: So, the trick is not have any false alarms, which is not easy and somewhat risky.
I hope so. Realize that if you have 10 phones on your LAN, which will use about 1 mbit/sec of VoIP traffic on your LAN (G.711), that's trivial for a 1000 mbit/sec network to handle. However, when that traffic hits the internet via your ISP, it's still 1 mbit/sec but running through a much narrower pipe. At 30 mbits/sec service from Sonic, you're probably on Fusion X2 (dual ADSL 2+) which is 30 Mbits/sec download, but only 2 Mbits/sec upload: The 1 Mbit/sec VoIP traffic is now gobbling about 50% of your upstream bandwidth. That's going to need QoS at the router to prevent your non-VoIP traffic from turning your VoIP to garble.
We have Comcast Business Class at my palatial office. It's shared between 4 small businesses and 5 security cameras. My guess is about
15 computers. There are 4 SIP phones in use. There is no QoS available in the Comcast router. At 25/3 Mbits/sec, if someone is doing a big upload, VoIP traffic gets garbled with even one phone. Comcast sells phone service and they are not going to be helpful by providing real QoS for anyone doing their own VoIP.
No experience with MonkeyBrains.
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
Let's compare some of the 200 series specs against the 500 series that you mentioned earlier. In this case a larger product number translates into a better, more expensive product.
SG500X-48P SG200-50P
capacity 130.95mpps 74.41mpps switching capacity 176Gps 100.0Gbps ACL rules 2K ??? MAC table 16K 8K CPU 800 MHz ARM ??? memory 256MB 128MB Flash 32MB 16MB SFP Max uplink 10GB 1GB hot swap yes ??? port binding yes ??? DHCP snooping yes ??? Price $2,758.55 $324.06
The cheaper switch is probably OK for a small business. Especially if the employees mostly use the network to surf the Inet. You can always purchase the more expensive switch at a later date, after you acquire a better understand as to why it costs more. With large networks you want to avoid being penny wise and pound foolish. Walmart's nobody's fool. They use 4500E switches. Although Win's criticism of the star topology is valid, in my experience every commercial enterprise requires access to at least one mission critical server that most employees continuously access. Ergo Walmart's star topology with the 4500E switches, whether Walmart likes it or not.
This comparison might help: "Compare the Cisco 200, 300 and 500 series switches" I'm a bit worried that the 200 series might not be stackable.
The "Auto Voice VLAN" feature should be useful for the VoIP phones.
Gotta run...
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Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
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