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# How can we evaluate  serious connectivity problem with in a specific range of distance?

Posted on 2005-04-02
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Consider4 buildings ,A,B ,C and D  the distance between  buildings  A and D is 1 mile and Band C are  in between A nd D.
Building A is completely wierd with FDDI and redundant connections from the switches to the servers.
Building D is wired completely with category 5 cabling ,with new compuetrs and fast ethernet cards,new switches and properly working routerssetup.As the network service enters the building over good category 5 cable.Whcih gets its service from Building C which in turns gets it service from building  B.
Building B has category 3wiring,and good network functioning.The hub in the building B basement connects directly to the Building A.

Between building B and D is the building C,which has category 5 cabling and an excellent functioning network.
It has no router as it houses its own servers.It has 10/100mbps switch in basement.which connects to both building B and D.
over category 5 cable.

All buildings have direct fuber connections for the phone system and there are extra runs for future technological\telephone services.

The Main question here is why is Building D finding the network so slow?How can we fix the problem at building D.Can anyone let me know what would be the solution for redundant network connectivity and what makes it to be relatively cheap to set up ,can anyone explain me the logic in this question briefly?
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Question by:anumit
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Expert Comment

ID: 13689261
Exactly what is slow in building D? All network traffic? Or traffic between C and D?

What speed is the connection between C and D running at? If the cable is over 100m it may be only 10Mbit/s

I imagine the *normal* setup would be to have each building on a separate subnet, connected by routers ... but this is outside my area of expertise ...
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Author Comment

ID: 13689312
Hi Giles Kennedy,Thaxs for the quick response.

Compared to all other buildings the network in building D is very slow.How can we fix the proble of slow down of network in building D ,to make the network fast.
The cable is more than  100m.
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Expert Comment

ID: 13689404
From what you are saying the problem is that the network INSIDE building D is slow?

How many computers are on teh network?

You need to check the status of each connection to the LAN - find out what speed it is running at (usually you can tell by looking at the LEDs next to the RJ45 socket). We want 100Mbit/s or, if you have gigabit switch and NICs, 1000Mbit/s.

What is your switch and router setup in building D?
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Accepted Solution

gpriceee earned 1600 total points
ID: 13689489
<|--------------- 1 mile -------------------|>
<|--->100m--|>
_____          _____          _____          _____
|        |        |        |        |        |        |        |
|  A    |------|  B     |------|  C    |------|  D     |
|____ |        |____ |        |____ |        |____ |
FDDI            CAT3           CAT5           CAT5
<|----|>HUB<|-------~Rtr--------|>Rtr
Solid                                10/100
Switch
Servers         ~srvrs          Own srvrs     ~Srvrs

Without knowing more, here are some options.
1. If you have fiber runs between the buildings, you might consider implementing them.  The max legth of a CAT5 Cable is 328 feet; any longer, and excessive collisions occur, along with dropped packets (assuming the punch down is perfectly within spec, along with the entire run--that exists without interference).  Use a Time Domain Reflectometer (TDR) to test the cables for overhead--the overall result from all specs.

2. It sounds like building D is looking for servers in building A.  In order to reach them, the data must pass through building C, which has no router.  How does bulding C pass the subnet traffic?  That could be a bottleneck too.  You might want to use netmon or a good sniffer to check the traffic in buildings B, C, and D.

3. Building B has a hub for its connection to building A.  It probably needs a hub for forgiving the CAT3 traffic, but building D seems to be relying on that very hub for its CAT5 traffic.  The CAT3 is an issue that might not have been noticed by building C because building C has its own servers.  It probably wasn't noticed by building B because its design seems as if it were made for the CAT3 cabling.  Now, building D needs to use that connection.  Typically, a hub also doesn't have the fabric to handle max loads; whereas a solid switch has a good fabric capable of at a minimum of handling all ports at a full load duplexed.  Also, a hub does not split collision domains; a switch does.

4. For building D to reach building A, it must affect traffic in buildings B and C.  If I understood your additional fiber layout, you have fiber runs among all of the buildings with extra, unused fiber strands.  I would implement fiber modules in at least building D.  At the very least, you could use the fiber to run directly from D to A.  An on-the-cheap method would be to run the fiber from a module in D to bullding C's fiber patch panel.  In building C's fiber patch panel, use a fiber patch cord to jump D's connection to the run from building B.  In building B's patch panel, use a fiber patch cord to jump B's connection to the run from building A.  Now, D is connected directly to A via a potential Gig connection.

Some potential bottlenecks existing now:
1. Hub in bulding B (collision domains and fabric).
2. Cat3 in  bulding B (CAT3 lay in-between CAT5's for building D's connection to A).
3. No router in building C (subnetted traffic forwarding).
4. >100m cable runs (excessive collisions and dropped packets).
5. Route from D to A (The explanation exludes D's need for any resources between D and A, so a direct connection to A would be better; A also could distribute the traffic better).
6. Unused fiber connections (Ultimately, C and D should have direct connections to A via fiber [B really doesn't matter because the CAT3 network won't improve from the connection anyway, unless interference exists in the run bwteen A and B])
7. Routing in building B (If it isnt clear which traffic has building C and D destinations, how does it get there?).
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Expert Comment

ID: 13689563
Further...  If your buildings are connected with copper, and each building has its own ground (which is required in the US), you have created a nightmare in the making....  Each building has a potential difference (electrical) and if you get a power spike, the current will look for the best way to ground.  If that is across the buildings through your wire, then that is where the current will flow, meaning that it will absolutely FRY any devices along the way...  Now this is just a simple explanation, but I think you get my drift...  Always, always use Fiber (or Wifi) to connect building in a Campus Area Network....

FE
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Expert Comment

ID: 13690071
Anumit -- It doesn't matter how many buildings are between A and D -- everything in D needs to connect directly to A, for their shares, and not try to go through intermediate buildings.  I.e. -- building D needs to have DIRECT connections to building A, B and C -- don't try to "daisy chain" them together.  Does this make sense, and if so, what is the problem when you try to connect building D directly to building A ????
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Expert Comment

ID: 13722048
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