WAN Operations WAN Standards

Modern WAN standards are defined and managed by a number of recognized authorities including the following:

TIA/EIA - Telecommunications Industry Association and Electronic Industries Alliance

ISO - International Organization for Standardization

IEEE - Institute of Electrical and Electronics Engineers

WANs in the OSI Model

Most WAN standards focus on the physical layer and the data link layer.

Layer 1 Protocols

Synchronous Digital Hierarchy (SDH)

Synchronous Optical Networking (SONET)

Dense Wavelength Division Multiplexing (DWDM)

Layer 2 Protocols

Broadband (i.e., DSL and Cable)

Wireless

Ethernet WAN (Metro Ethernet)

Multiprotocol Label Switching (MPLS)

Point-to-Point Protocol (PPP) (less used)

High-Level Data Link Control (HDLC) (less used)

Frame Relay (legacy)

Asynchronous Transfer Mode (ATM) (legacy)

EtherChannel Operation Advantages of EtherChannel

EtherChannel technology has many advantages, including the following:

•Most configuration tasks can be done on the EtherChannel interface instead of on each individual port, ensuring configuration consistency throughout the links.

•EtherChannel relies on existing switch ports. There is no need to upgrade the link to a faster and more expensive connection to have more bandwidth.

•Load balancing takes place between links that are part of the same EtherChannel.

•EtherChannel creates an aggregation that is seen as one logical link. When several EtherChannel bundles exist between two switches, STP may block one of the bundles to prevent switching loops. When STP blocks one of the redundant links, it blocks the entire EtherChannel. This blocks all the ports belonging to that EtherChannel link. Where there is only one EtherChannel link, all physical links in the EtherChannel are active because STP sees only one (logical) link.

•EtherChannel provides redundancy because the overall link is seen as one logical connection. Additionally, the loss of one physical link within the channel does not create a change in the topology.