Home | Articles | About | Contact | Forum |
Saturday, November 02, 2024



Lunarpages.com Web Hosting

Mailing List

E-mail:
By Joining the mailing list you will be notified of site updates.


Show Your Support For
This Site By Donating:











Audience: System Admins - Experts
Last Updated: 6/6/2011 1:47:37 PM
**All times are EST**






Multiplexing

By Erik Rodriguez

This article describes the method of multiplexing. It is a method used in date networks to send data from multiple sources through one physical line. Multiplexing is is used in conjuction with SONET and dark fiber.

Multiplexing has been around for ages. As a briefly mentioned above, multiplexing is used to send and receive multiple segments (or packets) of data. The main advantage of multiplexing is that you can send a lot data over 1 physical line. It was first used in telephone networks to relay voice conversations over twisted [wire] pairs. There are several types of multiplexing:

Frequency Division Multiplexing
Time Division Multiplexing
Dense Wavelength Division Multiplexing


Frequency Division Multiplexing (FDM)


FDM was developed to work with early telephone networks. It worked by dividing the freqencies to support multiple users. For instance, with a standard sound spectrum (20 Hz - 20,000 Hz) the frequencies would be equally divided to support 5 or so users per physical line. Note that in this case, users are given some of the frequency all the time. FDM is still used with cable TV, some older analog cellular systems, and most commonly YOUR FM RADIO! See the figure below:



Time Division Multiplexing (TDM)


TDM was developed later (late 1950's) with new "digital" technology. This works a little different than FDM, in that users are given all of the frequency some of the time. The way TDM actually works is pretty complicated, so I'm not going to explain it in much detail. However, the process involves converting signals from analog to digital. TDM not only allows more data to be sent over a physical medium, it provides a better quality of service (QoS). TDM comes in two flavors, Synchronous TDM and Statistical TDM. Synchronous TDM is widely used with T carriers and ISDN. Statistical TDM is more complex but more efficient. It makes better decisions about transmitting bandwidth.

Dense Wavelength Division Multiplexing (DWDM)


DWDM is a modification of TDM and FDM. It is sometimes called wave division multiplexing It performs the same function of multiplexing data, but it uses different colored lasers to send multiple channels over the same physical line. DWDM only runs over fiber optic lines but has an advantage because it can combine multiple connection types such as ATM, OC, etc into one physical fiber line. Now, DWDM works just like FDW in that it divides frequencies into channels. However, it uses a special "colored" laser to send each segment of frequencies. At first, this was a problem. If there were 14 channels all using a unique laser color, keeping extra lasers around (for each color) was expensive. Today, this problem is solved by using a special laser that can be "tuned" to any color in the event that one stops operating. If you look into DWDM more closely, you will be amazed how complex this method is.

So what is a Multiplexer?


A multiplexer is the device that performs the actual "data compression." It works much like a switch does on a regular LAN. They are generally very expensive depending on what type, brand, and features you want. It is pretty safe to assume that the general public does not shop for multiplexers. Below are some images of them from a carrier central office.

A front and back view of a DS3 multiplexer.






Contact Us

If you found this information useful, click the +1 button



Your E-mail:


Subject:


Type verification image:
verification image, type it in the box

Message:


NOTE: this form DOES NOT e-mail this article, it sends feedback to the author.


TCP vs. UDP
Juniper SRX anti-spam filtering config
Windows Server 2008 Clustering Configuration
Windows 2008 R2 Network Load Balancing (NLB)
Extreme Networks: Downloading new software image
Juniper SRX save config to USB drive
Juniper SRX logout sessions
Extreme Networks Syslog Configuration
Command line drive mapping
Neoscale vs. Decru
Data Security vs. Data Protection
Juniper SRX Cluster Configuration
HOWTO - Create VLAN on Extreme Switch
Using a Non-local Colocation Facility
Linux Server Administration
IT Chop Shops
Flow Viewers: SFLOW, NetFLOW, and JFLOW
Exchange 2007 Back Pressure
IPtables open port for specific IP
Politics in IT Departments
HOWTO - Block Dropbox
Cisco IOS Cheat Sheet
Subnet Cheat Sheet
Design a DMZ Network
How DNS works
Firewall Configuration
Juniper SSG Firewalls
Server Management
Configuring VLANs
Runlevels in Linux
Server Clustering
SONET Networks
The Red Hat Network
Server Colocation
Complicated Linux Servers
Dark Fiber
Data Center Network Design
Firewall Types
Colocation Bandwidth








Copyright © 2002-2016 Skullbox.Net All Rights Reserved.
A division of Orlando Tech Works, LLC
By using this site you agree to its Terms and Conditions.
Contact Erik Rodriguez