WAN Technologies

Question 1

What is WDM?

Answer 1

Wave Division Multiplexing is the act of using multiple different wavelengths within a single fiber cable to carry multiple signals. If a cable could carry a 51.Mbps signal replicated 150 times using different wavelengths, for example, it can build up to 7.6Gbps. This is done through different colored laser lights.

Question 2

Between CWDM and DWDM, which is often used internally for enterprise scenarios and which is better used in metropolitan areas?

Answer 2

CoarseWDM is simpler and used within enterprises due to it having less, but wider wavelength channels (about 18) (20nm spacing)(160km length)
DenseWDM is often used in MAN, or Metropolitan area networks. DWDM carries many more channels (40, 80 or 160) using its much narrower wavelength channels. (much further reach than CWDM)

Question 3

What is MPLS?

Answer 3

Multiprotocol Label Switching (MPLS) is a routing technique in telecommunications networks that directs data from one node to the next based on labels rather than network addresses

In an MPLS network, labels are assigned to data packets. Packet-forwarding decisions are made solely on the contents of this label, without the need to examine the packet itself. This allows one to create end-to-end circuits across any type of transport medium, using any protocol. The primary benefit is to eliminate dependence on a particular OSI model data link layer (layer 2) technology, and eliminate the need for multiple layer-2 networks to satisfy different types of traffic.

These are split into the following per packet:

Label ( 20 bits) Instructs on where the packet should be delivered to

Experimental Bits (3 bits) (Marks the importance of a packet over others)

Bottom of Label Stack (1 Bit) Indicates that this is the first of a series of incoming labels.