Rack of Ethernet switches.

WAN Link Specifications

Wide-Area Networks

Wide-Area Networks or WAN links are telecommunications infrastructure connecting networks across broad geographic areas. They typically have the topology of point to point connections. This is what carriers and backbone providers use to connect cities.

Digital Signal X is a series of digital transmission rates based on DS0. The North American T-carrier and European E-carrier systems use these:

DSX Bit rate Number of DS0 links
multiplexed together
with TDM
Used for
DS0 64 Kbps One telephone voice channel
DS1 1.544 Mbps 24 T1
2.048 Mbps 32 E1
DS1C 3.152 Mbps 48
DS2 6.312 Mbps 96 T2
8.448 Mbps 128 E2
34.368 Mbps 512 E3
DS3 44.736 Mbps 672 T3
139.264 Mbps 2048 E4
DS4/NA 139.264 Mbps 2176
DS4 274.176 Mbps 4032
565.148 Mbps 8192 E5

The T-carrier system was introduced by Bell in the U.S. in the 1960's. It uses time-division multiplexing to interleave multiple pulse-code modulation signals on a shielded conductor in each direction. Twisted pair at lower speeds, coaxial cables or optical fibre at higher speeds. E-carrier is similar, used in Europe. E-carrier can support higher data rates for a given bit rate as it uses all eight bits per channel for signal coding.

SONET (Synchronous Optical Network) is much faster — you're generally talking about Internet backbone links.

Format Data rate
T1 1.544 Mbps
E1 2.048 Mbps
T1C 3.152 Mbps
T2 6.312 Mbps
E2 8.448 Mbps
E3 34.368 Mbps
T3 44.736 Mbps
T3D 135 Mbps
E4 139.264 Mbps
E5 565.148 Mbps
Format Data rate
OC-1 51.84 Mbps
OC-3 155.52 Mbps
OC-12 622.08 Mbps
OC-24 1.244 Gbps
OC-48 2.488 Gbps
OC-192 10 Gbps
OC-256 13.271 Gbps
OC-768 40 Gbps
DS3 interfaces on a Cisco 7000 series router.

DS3 interfaces on a Cisco 7000 series router.

And then there's a grab-bag of other technologies:

Format Data rate
GSM mobile telephone 9.6-14.4 kbps
POTS (Plain Old Telephone Service) Up to 56 kbps
GPRS (General Packet Radio System) 56-114 kbps
ISDN BRI 64-128 kbps
IDSL 128 kbps
Frame relay 56 kbps — 1.544 Mbps
DSL 512 kbps — 8 Mbps
SDSL, HDSL 1.544 Mbps
ADSL 16—784 kbps upstream, 1—9 Mbps downstream
VDSL Up to 52 Mbps downstream (max distance 1000-4500 feet)
Cable modems 512 kbps — 52 Mbps
10 Mbps or less to node
HSSI (High-Speed Serial Interface),
up to 50 feet router-to-WAN connection
Up to 53 Mbps
FDDI (Fiber Distributed Data Interface),
used for corporate/campus WANs
100 Mbps
Cisco V.35 WAN cable.

Cisco V.35 cable used to connect to a T1/DS1 WAN link.

James Bamford's The Shadow Factory: The NSA from 9/11 to the Eavesdropping on America is an investigative history of the NSA over the period 2001-2008. It summarizes the U.S. landing points of many of the trans-ocean communication cables and some major U.S. IXP (Internet Exchange Point), MAE (Metropolitan Area Ethernet, a form of IXP), and NAP (National Access Point) sites:

ASIN: 0307279391


San Luis Obispo, California is the AT&T landing point for five out of six trans-Pacific cables. They come in under the beach at Montana de Oro State Park and run "2,200 feet through a 5-inch drill pipe to a manhole," then run a mile to 9401 Los Oso Valley Road in San Luis Obispo.

San Francisco, California notoriously has the major IXP on the 7th floor of 611 Folsom Street. One floor down is room 641A, labeled "SG3" for "Study Group 3", where the NSA captures traffic with a Narus STA 6400.

San Jose, California has MAE West on the 11th floor of 55 Market Street.

Los Angeles, California has the Any2 Exchange at One Wilshire. It is a major interconnection point for the Pacific Rim countries.

60 Hudson Street, New York, a major telecommunications point.  Over 100 telecommunications companies occupy a carrier hotel with a major meet-me room.

60 Hudson Street, the former Western Union Building and still a major telecommunications interconnection point.

New Jersey / New York

Tuckerton NJ and the surrounding area is the landing site for a number of cables to Europe, the Caribbean, and South America.

New York, New York has 60 Hudson Street, the former Western Union Building and its headquarters until 1973, and still a major world communications nexus. It's a carrier hotel with over 100 telecommunications companies interchanging Internet traffic. Another major carrier hotel is at 60 Broad Street, just off Wall Street.

See my page dedicated to the visible telecommunications infrastructure in Manhattan for more.

Virginia / Washington DC

Vienna, Virginia has MAE East at Suite 400, 8100 Boone Boulevard. It used to be in the corner of the parking garage.... That's just across Leesburg Pike from the Tysons Corner Shopping Center.

Ashburn VA has the Equinex IXP at 21830 UUNET Way.


Miami, Florida has the NAP of the Americas at 50 NE 9th Street. It's owned by Terramark and routes traffic between Latin American countries and handles about 90% of the traffic between North and South America.


Bridgeton, Missouri is the site of AT&T's Network Operations Center, at 12976 Hollenberg Drive.

There are many more, see these links for lists:

Frost forming on liquid nitrogen dewars on a corner of Broadway in the Financial District in lower Manhattan.

Frost forming on the cold dewar from which liquid nitrogen is being drawn.

Two liquid nitrogen dewars on a corner of Broadway in the Financial District in lower Manhattan.

Two liquid nitrogen dewars on the corner of Broadway and John Street on the edge of the Financial District in Lower Manhattan. Nitrogen is most efficiently stored and transported in liquid form. The red hose running across the sidewalk and down into the manhole provides a constant supply of dry nitrogen for the conduits carrying the many telecommunications circuits running underground.

This is the Verizon switching center on Charles Street at East Pleasant, in Baltimore, Maryland. You know that there has to be a fat pipe between here and the nearby Fort Meade.

Verizon telecommunications switching center, Charles Street at East Pleasant, Baltimore, Maryland, view looking south on Charles Street.
Verizon telecommunications switching center, Charles Street at East Pleasant, Baltimore, Maryland.
Verizon telecommunications switching center, Charles Street at East Pleasant, Baltimore, Maryland, view looking north on Charles Street.

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