Rane NM 48 - Manual (Page 10)

Manual-10
Mbit Ethernet, that link will easily saturate. In any case, it is
not CobraNet which suffers under these conditions, it is the
computers.
The final disadvantage using multicast transmission is the
inability to reliably share computer network data and
CobraNet data on the same network. This is not to say that it
is impossible, it indeed works. However, the problem is that
the network bandwidth required by the computer data is ever-
changing and not controlled or monitored by the CobraNet
devices. Thus, when the computer data suddenly and unpre-
dictably requires more bandwidth than is available, the entire
network bogs down creating computer data collisions which
slow down the computer network, and simultaneously creates
audio dropouts, pops or ticks. Not fun, or necessary.
Oftentimes however, computer data must be shared on the
network or not all audio channels are required at every node.
This is where unicast networking comes in.
Unicast Network example [a.k.a. point-to-point]
using more flexible switches
A second way to send audio over the network uses a
different scheme called unicast – or point-to-point. You must
use unicast when you require only certain locations on the
network to receive certain channels. For example, in a
campus-sized church complex, it may be useful to send all
channels from the live band mics to the front of house (FOH)
mixer, monitor mix location and to the recording studio. But
the left-center-right (LCR) audio feed to the overflow
building across the street only needs three channels. The
stereo FM broadcast room only needs a stereo mix and the
video truck which is used only every other week may require
all channels.
In the above case, it is not required, overly complex, and
most importantly, expensive to send all channels to all
locations. Thus, a unicast (point-to-point) network to feed the
mic channels from the stage to the four required locations –
FOH, monitor, recording studio and video truck – is required.
Therefore, using Bundles starting at 256 or above, sends the
audio over Unicast Bundles which forces the use of network
switches (not repeater hubs) which support unicast data.
Network Hardware Device Advantages Disadvantages/Limitations
Repeater hubs
Operate half duplex; i.e., they cannot
transmit & receive simultaneously.
Thus, a 100 Mbit network is 100 Mbit
network-wide.
Very inexpensive (but likely going
away). Perfect when a dedicated
CobraNet network is needed and all
audio data is required at all CobraNet
nodes.
Cannot place a computer or computer
data on the same network with
CobraNet data using repeater hubs.
There is a fixed maximum of 8 Bundles
permitted on a repeater hub network. On
repeater networks, all devices must
operate at the same data rate and in half
duplex mode. Must obey network
diameter restrictions. As repeater hubs
are added to a network, the network
bandwidth is divided/shared across
network devices.
Switches (unmanaged)
Operate full duplex enabling
simultaneous transmit and receive. Thus,
100 Mbit networks are 100 Mbit in each
direction; 200 Mbit total per switch
port!
As switches are added to a network, the
network's bandwidth increases. Some
switches provide fault tolerance features
(i.e., managed switches) and interfaces
to other media (i.e., fiber) or network
technologies (i.e., ATM). No network
diameter restrictions (like repeater hubs
have).
[Using switch-based networks removes
CobraNet's need to detect collisions, thus
CobraNet acts differently with repeater vs. switch-
based networks — although this is not important
to know or understand for design or proper
operation.]
Only slightly more expensive than
repeater hubs; it is well worth the
(literally) few extra dollars more for a
switch than a repeater hub.
Managed Switch
Managed switches are like switches on
steroids; they offer many customizable
setup features.
Permit extremely flexible setup,
diagnostics and troubleshooting
capabilities. Although managed switches
are more expensive than non-managed
switches, these capabilities more than
pay for themselves when network re-
configuration or troubleshooting is
required, particularly during setup.
More costly than non-managed
switches, but worth the expense for
many systems due to their advantages.
Table 2. Network Hardware