VT1.5

VT1.5 is a type of virtual tributary in <a href="/facts/SONET/G3LgtGS6">SONET</a>.
SONET <a href="/facts/Bandwidth_(computing)/lY6Tb4gX">bandwidth</a> is defined in multiples of an <a href="/facts/Optical_Carrier/GVABpoYY">OC-1</a>/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 <a href="/facts/North_America/djNjCQIl">North America</a> and <a href="/facts/Japan/U5mz0SRT">Japan</a>, the VT1.5 is the most common virtual tributary because it can carry 1.544 Mbit/s; just enough room for a <a href="/facts/Digital_Signal_1/cghJPRpQ">DS1/T1</a> signal. In <a href="/facts/Europe/DTAtrKfh">Europe</a>, the VT2 (with a data rate of 2.304 Mbit/s) is used to transport <a href="/facts/E-carrier/h0MXcgXN">E1s</a>.
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

<ul><li>VT 1.5 (DS-1: 1.544 Mbit/s)</li>
<li>VT 2 (E-1: 2.048 Mbit/s)</li>
<li>VT 3 (DS-1C: 3.152 Mbit/s)</li>
<li>VT 6 (DS-2: 6.312 Mbit/s)</li></ul>
7 VT groups (VTG) per STS-1.

<ul><li>Four DS-1s map into one VTG.</li>
<li>One STS-1 frame can carry 28 DS-1s</li>
<li>DS-3 Maps directly to STS-1. VT are not needed.</li></ul>

VT1.5 open-in-new

VT1.5