WAN Technologies

SONET

The primary fiber-optic cable carriers settled on a single international standard called Synchronous Optical Network (SONET) in USA Synchronous Digital Hierarchy (SDH) in Europe for handling the interconnections of long-distance Internet routers.

• SONET defines interface standards at the Physical and Data Link layers.
• SONET ring has fault tolerance in case of line loss so many of the big long-distance optical pipes for the word’s telecoms networks are SONET rings.
• SONET establishes Optical Carrier speeds from 51.8 Mbps to 39.8 Gbps.

Fiber Improvements

Many fiber devices use a very clever feature called bidirectional wavelength division multiplexing (WDM or BWDM) or its popular version, dense wavelength division multiplexing (DWDM). that enables an individual single-mode fiber to carry multiple signals by giving each signal a different wavelength (using different colors of laser light).

• The result varies, but a single DWDM fiber can support ~150 signals, enabling, for example, a 51.8-Mbps OC-1 line to run at 51.8 Mbps × 150 signals = 7.6 gigabits per second!
• A related technology, coarse wavelength division multiplexing (CWDM), is simpler than DWDM used in higher-end LANs with 10GBASE-LX4 networks.
• SONET has mostly been replaced with a mix of optical links such as 100, 400 Gigabit Ethernet, and … .

Private WANs

Many organizations connect far-flung network resources through private connections rather than across the Internet. They purchase a dedicated, secure and expensive connections (leased lines) with no fear of hackers accessing network resources.

MPLS

Multiprotocol Label Switching (MPLS) provides a platform-agnostic labeling system to greatly improve performance compared to an IP network in a private network of dedicated leased line to make direct or more efficient connections by providing network-wide quality of service (QoS).

• The MPLS header parts
• MPLS adds an MPLS label that sits between the Layer 2 header and the Layer 3 header (always IP).
• Routers avoid using their routing table instead they use the MPLS header information to route packets quickly.
• MPLS routers leverage their existing dynamic routing protocols to exchange information about their overhead. → QoS to be applied across an entire group of routers rather than just one router and maintains high security as well.
• MPLS terms: