SONET/SDH aggregates a number of lower-speed electrical or optical signals into a single higher bit rate signal for transmission over a single fiber using a single wavelength. Time division multiplexing (TDM) or statistical TDM is used.
DWDM assigns incoming optical signals to specific frequencies or wavelengths of light and multiplexes them for transport over a single fiber. WDM is a form of frequency division multiplexing.
Advantages of WDM: each wavelength of light can carry a signal with its own speed and protocol, independent of what's on the other wavelengths. And all signals arrive at the same time, instead of being distributed across time slots.
SONET/SDH can be carried over WDM; but not vice versa.
I think the easiest way to understand it is that SONET runs at the 1.5 layer while DWDM runs purly at the optical layer. If you wanted to, DWDM equipment doesn't even need SONET, you could run a 10G Ethernet circuit directly over one fiber that gets muxed right along a SONET OC-192. Unless you work with it and see how it all gets optically switched it is a little hard to grasp at first.
DWDM/WDM are technologies that improve the capability of optical cable in carrying data by multilexing many channel of wave_lengths
SONET/SDH are technologies that are used as a buffer (interfacing) layer for higher layers (IP/ATM...) access the huge capability of Optical transmission system (Optical fiber)
SONET/SDH is located at the layer one if you want to have a visual view.
I think Optical Layer has another diffrent meaning: In the Optical Internet model, **Optical Layer** has a very important role as Network Layer in TCP/IP model, so it's maybe not belong to **Physical Layer**
This is actually a pretty cool feature, i didn't even know it existed until I was looking for a solution to advertise a subnet (prefix in BGP talk), only if a certain condition existed. This is exactly what conditional advertisements does
j ai une question j ai achete un routeur cisco 887VA-k9 , je le configuré avec la configuration ci- dessous
si je le lier avec mon pc portable sur l un de ses ports directement ça marche toute est bien ( la connexion internet + m...
Attached policy provides CLI access to the Cisco 4G router over text messaging. Two files are in the attached .tar file:
2. PDF with instructions on how to load and use the .tcl file.