• Status: Solved
  • Priority: Medium
  • Security: Public
  • Views: 429
  • Last Modified:

Trying to understand the ANSI/TIA/EIA-568-B, but I am getting confused by some of the terms. Warning - one answer might lead to another question.

I am reading through the ANSI/TIA/EIA-568-B standard from a link on the web.  I have attached a pdf file of what I am reading so anyone can peak at my source.  I am trying to understand the maximum cable lengths they mandate, but first must understand what they mean by some key terms.

What is a horizontal cross-connect?  I picture a punch block where wires are terminated and short cat5e patch cables connect various wires on one side to various wires on the other side.

What is an Intermediate Cross-Connect?  I cannot picture this.  Please bear with me.  I have experience in the IT field working with Cat5e cabling between routers, switches, and computers, but have only glanced at the room in back with all the phone wires, the T1 thing (that should give away my exposure), and the other mysterious black box.

What is a Main Cross-Connect?  Have a picture much like a moonless night deep in the forest where I can't see my own hand in front of my face.

What does the standard classify a switch or router as?  

Part of the stimulus for these questions and this self education is my current employer has an ad-hoc network.  Often I am instructed to remove equipment using an Ethernet cable, then coil the cable, and lay on top of the drop ceiling tiles.  I hate doing this.  Also, there are runs where a cable comes off a switch in the basement, goes upstairs to another switch, then to a switch in a closet, and then finally a cable connects to a computer.  How is a switch treated when considering maximum cable lengths?  Is a switch a kind of cross connect?  Once I understand this better, I may have more questions.  I wish I could offer more than 500 points for this!

Really appreciate the guidance.  

1 Solution
Easy ones first, but don't get too bogged down in terminology..

>How is a switch treated when considering maximum cable lengths?
A switch is a repeater. The max distance is from a switch to another switch or from a switch to a host computer.

>What is a horizontal cross-connect?
This would typically be a patch panel where a bundle of cables would terminate in one patch panel in one closet, run horizontal (in ceiling generally) to another closet terminated in another patch panel.
Vertical would be the same, only between floors. More often than not, the vertical distance is greater and fiber cable may be more appropriate.

A Main cross connect might be a central room that has a patch panel connecting to the East wing closet and another patch panel connecting the West wing closet an another patch panel connecting floors above and below.
If the total distance between the East and West closets is short enough, you could potentially "cross connect" the two patch panels in the center and create a single run from East to West. Typically, we would put a switch in the center so that the distance does not matter.

The graphic on page 2 shows this concept. "common equipment" would be a switch.
Mark DamenERP System ManagerCommented:
Going back a step, what are you trying to understand it for....  is it to pass an exam, or is it just learning about the "back end" or patch panel?

>How is a switch treated when considering maximum cable lengths?
>A switch is a repeater. The max distance is from a switch to another switch or from a switch to a host computer.

Um actually... a switch is ... ready for this? ...   a switch.  A hub is a repeater. Switches - generally speaking- eliminate the need to worry about bit-time on the wire which eliminates the need to worry about how far apart the furthest ends of the network are. A hub or a repeater just repeat the signal with no buffereing and cause a situation where there is a physical limit to the network size that you do not see with switches. Anyone remember the 5-4-3 rule... or 5-4 for UTP with hubs? With hubs and repeaters there is a physical limit to the size of the network totaling 500m maximum from end-to-end on the longest path.

A switch is considered an endpoint for the 100m cable connection. The other end is usually another switch or a computer. Max between any of these three is 100m including patch cables. Or 90m in the horizontal/vertical between panels or between a panel and a wall jack plus 10m in patch cables. A router, in this context, has the same action as a switch as it acts as an endpoint for the network and therefore does not affect the maximum lengths allowed.

Horizontal cross-connect is the location where all of the horizontal runs in a facility or zone are consolidated into a patch panel. These runs then are usually attached to a switch at this location.

Intermediate cross-connect is the location where feeds to the horizontal zones (or vertical zones) may be consolidated. Sometimes fed by a switch, other times just a patch from panel to panel. If you have small panels, they may be used as intermediate panel as well as horizontal in the same panel.

Main cross-connect is the location where your primary wiring facility is located. This can either feed horizontal cross-connect locations directly, or can feed an intermediate cross-connect panel which then feeds the horiziontals from there.

You are allowed 1 interconnect in the horizontal 90m run. Usually a Consolidation Point or CP as mentioned in the document you were reading. This is used for facilities that change alot. You put a small patch panel near the area that changes, and then you add and remove runs as needed to the workstations which still have a normal jack at the station. In my opinion its a little goofy, because you actually go from a plug at one end to a jack on the other in the horizontal run from the CP. Although you could just use a really long patch cable. (but you have to shorten your mid-run to accomodate this)

mmmm ... sleeepy now hope I didn't screw this up too much or spelled too poorly.

What is a horizontal cross-connect?
The cabling in the wall/ceiling/floor which is horizontal.  For instance, from a wall jack to a closet/Intermediate Cross Connect/Intermediate Distribution Frame/Equipment Room.

What is an Intermediate Cross-Connect?
I call them Network Closets.  A small room (usually) where larger feeds are "split" and distributed.  We have one on each floor.  We have say 200 patch panel ports and 10 switches.  There are patch cables from the patch panels to the switches.  The switches are in turn connected back to the Main Cross Connect via fiber.

What is a Main Cross-Connect?
Your main cross connection area/field.  In the telephone world - a wall where big thick cables come out of the PBX onto 66 blocks and then jumper across to other 66 blocks where they terminate onto thick cables which go off to the Intermediate Cross Connects.  In data - the patch panels where your main switching gear connects into and is distributed to other switch panels.  

What does the standard classify a switch or router as?
Equipment.  It may be called Customer Premesis Equipment.  To further muddy things - it can be DTE (Data Terminal Equipment) or DCE (Data Communications Equipment).  Think of DTE as a PC, DCE as a switch and then it makes sense.  If the equipment is the end of the line, it's likely DTE.  If it's involved in communicating between other devices, it's likely DCE.

 then coil the cable, and lay on top of the drop ceiling tiles.
This is a violation of the National Electrical Code in the US - and also a likely violation of local Fire Codes.  If you are instructed to do it, I would recommend you politely, and politically, point out the error in doing it and why, in writing - to CYA.

How is a switch treated when considering maximum cable lengths?
Now you're talking about Ethernet standards which are related, but not the same as cabling standards.  The switch will receive the signal, and assuming it is a good signal, will send it on it's way again by repropagating the signal.  So, you can do 100' between switches over copper (10baseT, 100baseT, 1000baseT) no problems.

Is a switch a kind of cross connect?
No.  It's equipment.  Not related to cabling.  Cross connects refer to cabling.



I hope this helps.
I agree with all above. But for better imagination look here:
and download PDF called Anixter Standards Reference Guide , there is explanation with pictures.
Question has a verified solution.

Are you are experiencing a similar issue? Get a personalized answer when you ask a related question.

Have a better answer? Share it in a comment.

Join & Write a Comment

Featured Post

Improve Your Query Performance Tuning

In this FREE six-day email course, you'll learn from Janis Griffin, Database Performance Evangelist. She'll teach 12 steps that you can use to optimize your queries as much as possible and see measurable results in your work. Get started today!

Tackle projects and never again get stuck behind a technical roadblock.
Join Now