Datasheet

810
Introducing WANs
60-pin serial cable may be EIA/TIA-530, EIA/TIA-449, EIA/TIA-232, V.35, or
X.21 standard connectors, which I examine in the following section.
✦ High-Speed Serial Interface (HSSI): A proprietary smart-serial DTE/DCE
interface developed by Cisco Systems and T3plus Networking for use in
high-speed WAN link communications.
HSSI operates at the physical layer of the OSI model and uses a male,
subminiature 50-pin connector with a maximum cable length of 50 feet.
HSSI provides data transmission rates approaching 52 Mbps by employ-
ing differential emitter-coupled logic (ECL). ECL technology enables low
noise and high-speed data communications. HSSI uses a series of four
loopback tests and two control signals to validate the communications
process. These communication checks provide handshaking, internal
self testing, and high reliability features.
DCE serial interfaces
Several types of serial interface standards for WAN communications have
been defined by the Electronic Industries Alliance/Telecommunications
Industry Association (EIA/TIA). The following connectors may be used to
connect to a router’s serial port:
✦ EIA/TIA-530: The standard for synchronous balanced and unbalanced
serial interfaces using inexpensive DB-25 connectors.
EIA/TIA-530 defines a cabling interface standard between a DTE and DCE
device. Differential signaling is used to send high-speed data over long
cable using a combination of send, receive, clocking, control, and hand-
shaking signals to send high-speed data over long cabling. Even though
the EIA/TIA-530 standard reduces the amount of signal pins used from
a 37-pin connector to a 25-pin connector, the most critical electrical sig-
nals are carried over and maintained on the 25-pin connector.
✦ EIA/TIA-449: A synchronous serial interface standard used for data net-
working communications that uses a smaller and less expensive connec-
tor than V.35 types.
EIA/TIA-449 signals may travel greater distances than the EIA/TIA-232
standard and support data transfer rates up to 2Mbit/s. The Cisco CAB-
449MT cable uses a male DB-60-pin connector (Cisco end) to a male
DB-37-pin connector (network end).
✦ EIA/TIA-232: An asynchronous serial interface that uses 9-pin (DB-9) and
25-pin (DB-25) connectors popular on all types of DCE/DTE equipment, per-
sonal computers, modems, terminals, and older printers. The EIA/TIA-232
standard is used to transfer binary data between a DCE and DTE device.
Generally, computer serial ports use DTE male pins and DCE devices (such
as modems and other networking equipment) employ female connectors.
Male-to-female and female-to-male gender changers are available. EIA/TIA-
232 cable lengths are restricted to 50 feet (15 meters).
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