Long ethernet
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Posted by grisley on June 12, 2006, 7:47 am
Please log in for more thread options Hi, We have to connect 32 dataloggers, separated 500m from each other (16km total) with an ethernet LAN. We're going to place 32 fiber optic switches close to each datalogger, and an utp link from switch to the datalogger. I think this network is excesively long due to ehernet inherent CSMA/CD timing considerations, and that we should split the network up using routers into smaller sub-networks. On the other hand, traffic is going to be quite low. Will it work like this or we should definitely add routers/bridges? Thanks | |||||||||||||||||||||||||||||||
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Posted by William P.N. Smith on June 12, 2006, 8:37 am
Please log in for more thread options You are going to place one switch close to each datalogger, yes? >I think this network is excesively long due to ehernet inherent CSMA/CD
>timing considerations, and that we should split the network up using >routers into smaller sub-networks. On the other hand, traffic is going >to be quite low. If it's full-duplex, you won't have collisions, and if the traffic is low enough to prevent overflowing buffers in your switches, you shouldn't lose any data. | |||||||||||||||||||||||||||||||
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Posted by glen herrmannsfeldt on June 12, 2006, 3:55 pm
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grisley wrote: > Hi,
> We have to connect 32 dataloggers, separated 500m from each other (16km > total) with an ethernet LAN. We're going to place 32 fiber optic > switches close to each datalogger, and an utp link from switch to the > datalogger. > I think this network is excesively long due to ehernet inherent CSMA/CD
> timing considerations, and that we should split the network up using > routers into smaller sub-networks. On the other hand, traffic is going > to be quite low. If the long links are full duplex, then there is no CSMA/CD problem. Otherwise, for 10baseFL (10 megabit/s) you should be fine unless you daisy chain them. -- glen | |||||||||||||||||||||||||||||||
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Posted by on June 12, 2006, 4:18 pm
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glen herrmannsfeldt wrote: > grisley wrote:
> > Hi,
> > We have to connect 32 dataloggers, separated 500m from each other (16km > > total) with an ethernet LAN. We're going to place 32 fiber optic > > switches close to each datalogger, and an utp link from switch to the > > datalogger. >
> > I think this network is excesively long due to ehernet inherent CSMA/CD
> > timing considerations, and that we should split the network up using > > routers into smaller sub-networks. On the other hand, traffic is going > > to be quite low. >
> If the long links are full duplex, then there is no CSMA/CD problem. > Otherwise, for 10baseFL (10 megabit/s) you should be fine unless you > daisy chain them. You will need to provide further details however:- Assuming that the switches are:- Full Duplex on the Fiber Optic ports at 10 or 100 or 1000 Mbps OR Are 10 Mbps There there is no problem with CSMA/CD The only way there could be an issue is with 100 HD where the max length is 200M (IIRC) The standard (IEE 802.1d) does say however that the maximum network diameter is 8 bridges (bridge=switch pretty much). This though really applies to the Spanning Tree Protocol and I think that unless you need STP for redundant links then there will be no problem. Even if you want to use STP I find it hard to imagine that it will not work since the standard was written years ago and took into account slower links and lower capacity switches. I have never tried a network of > a few switches in diameter.
AH! Oh yes I have. Years ago my company used to test switches by configuring them with a lot of vlans with two ports in each. These VLANs were then connected by crossover cables making a very long network and a pair of PCs were used to ping through the lot. It worked. This was done with dozens of VLANs. If you do want to stick to the standard you will need 4 routers to break the 32 nodes into 4 x 8 switch (approx) sections. | |||||||||||||||||||||||||||||||
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Posted by stephen on June 12, 2006, 4:15 pm
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> Hi,
> We have to connect 32 dataloggers, separated 500m from each other (16km > total) with an ethernet LAN. We're going to place 32 fiber optic > switches close to each datalogger, and an utp link from switch to the > datalogger. > I think this network is excesively long due to ehernet inherent CSMA/CD > timing considerations, and that we should split the network up using > routers into smaller sub-networks. On the other hand, traffic is going > to be quite low. since you are using switches, each fibre link is a separate CSMA/CD domain. As long as the fibre links operate as full duplex you can support several Km per link. Note that since you only want low capacity, you are better running at 100 Mbps rather than 1000. That way you can use multimode fibre 100 Base-FX interfaces. If you use Gigabit then you either need 1000 Base-LX interfaces, or good quality fibre - multimode interfaces and fibre are limited to 260m or so > Will it work like this or we should definitely add routers/bridges?
> the switches are bridges - so fine > Thanks
--
> Regards stephen_hope@xyzworld.com - replace xyz with ntl | |||||||||||||||||||||||||||||||
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>total) with an ethernet LAN. We're going to place 32 fiber optic
>switches close to each datalogger, and an utp link from switch to the
>datalogger.