VT1.5 is a type of virtual tributary in
SONET
Synchronous optical networking (SONET) and synchronous digital hierarchy (SDH) are standardized protocols that transfer multiple digital bit streams synchronously over optical fiber using lasers or highly coherent light from light-emitting diode ...
.
SONET
bandwidth
Bandwidth commonly refers to:
* Bandwidth (signal processing) or ''analog bandwidth'', ''frequency bandwidth'', or ''radio bandwidth'', a measure of the width of a frequency range
* Bandwidth (computing), the rate of data transfer, bit rate or thr ...
is defined in multiples of an
OC-1/STS-1, each of which can transport up to 51.84 Mbit/s. However, it is frequently desirable to address much smaller portions of bandwidth. To meet this need, sub-STS-1 facilities called Virtual Tributaries have been defined. In
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...
and
Japan
Japan ( ja, 日本, or , and formally , ''Nihonkoku'') is an island country in East Asia. It is situated in the northwest Pacific Ocean, and is bordered on the west by the Sea of Japan, while extending from the Sea of Okhotsk in the north ...
, the VT1.5 is the most common virtual tributary because it can carry 1.544 Mbit/s; just enough room for a
DS1/T1 signal. In
Europe
Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the weight of its history and traditions. Europe is also considered a Continent#Subcontinents, subcontinent of Eurasia ...
, the VT2 (with a data rate of 2.304 Mbit/s) is used to transport
E1s.
Some SONET manufacturers offer products that can switch at the VT1.5 level. Such equipment is able to re-arrange the data payloads so that inbound VT1.5s are placed into a completely different set of outbound STS's than the ones they arrived in. Among other things, this allows the bandwidth usage to be optimized and facilitates a cleaner network design.
The following is provided via Network Infrastructure/Design Student:
Four types of VT's defined in SONET
*VT 1.5 (DS-1: 1.544 Mbit/s)
*VT 2 (E-1: 2.048 Mbit/s)
*VT 3 (DS-1C: 3.152 Mbit/s)
*VT 6 (DS-2: 6.312 Mbit/s)
7 VT groups (VTG) per STS-1.
*Four DS-1s map into one VTG.
*One STS-1 frame can carry 28 DS-1s
*DS-3 Maps directly to STS-1. VT are not needed.
External links
"Understanding Sonet VTs: A Tutorial"
Network protocols
Synchronous optical networking