Manual-14
Conductor – The CobraNet device on the network which
supplies the master clock. A conductor arbitration proce-
dure insures that at any time there is one, and only one,
conductor per network. The conductor transmits beat
packets at a regular interval. The time interval between
beat packet transmission is the mechanism of clock
delivery. The conductor is also responsible for generating
transmission permissions based on forward reservations
received in reservation packets. The transmission permis-
sions are published in the beat packet.
Crossover cable – A special network cable that allows two
network devices to connect directly together without the
need for a hub. The receive and transmit pairs must be
swapped within the cable.
One End
Cable
the Other End
TR+ pin 1
———
pin 3 RCV+
TR- pin 2
———
pin 6 RCV-
RCV+ pin 3
———
pin 1 TR+
RCV- pin 6
———
pin 2 TR-
Since a normal (non-crossover) network cable physically
looks like a crossover cable, one of three practices are
suggested: clearly label all crossover cables so they are not
confused with normal “standard” ethernet cables. Wire two
female wall plate jacks back to back with the proper
swapping and use this adapter as a 2 port hub. Another
useful adapter uses a standard RJ-45 at one end and a
female wall jack at the other cross-wired. Making these
two adapters short helps avoid confusing standard network
cables from crossover cables. See http://
www.peakaudio.com/cobranet/network_cabling.htm.
Fully Switched Network – A network built entirely from
Switching Hubs. With the elimination of Repeater Hubs,
the collision condition is removed from a fully switched
network.
Hub – Hub is not a technically concise term. The term can be
used to refer to either a Repeater Hub or a Switching Hub.
Isochronous – Uniform in time; of equal time; performed in
equal times; recurring at regular intervals. An isochronous
data stream is characterized by the fact that data delivered
late is unusable. Live audio and video are examples of
isochronous data streams.
Media Converter – A two port Repeater Hub with different
media types on each port. Media converters can convert
between CAT5 Cable and Fiber.
Multicast – See Multicast addressing.
Multicast addressing – Data which is Multicast is addressed
to a group of, or all devices on a network. All devices
receive multicast addressed data and decide individually
whether the data is relevant to them. A Switched Hub is
typically not able to determine appropriate destination port
or ports for multicast data and thus must send the data out
all ports simultaneously just as a Repeater Hub does.
Multicast addressing is to be avoided whenever possible
since it uses bandwidth network wide and since all devices
are burdened with having to decide whether multicast data
is relevant to them.
Network Channel – Old term now called Bundle. (Hey,
Bundle is a Peak Audio term, so call them.)
Packet – A series of bits containing data and control informa-
tion, source and destination addresses and formatted for
transmission from one node to another.
Performer – All units except the conductor operate as a
performer. A performer must re-synthesize a sample clock
based on arrival times of received beat packets. A per-
former may transmit isochronous data packets only if given
transmission permission to do so by the conductor.
Repeater Hub – An Ethernet multi-port repeater. A data
signal arriving in any port is electrically regenerated and
reproduced out all other ports on the hub. A repeater hub
does not buffer or interpret the data passing through it. If
data signals arrive simultaneously from multiple ports, a
collision condition is recognized by the hub and a special
jam signal is transmitted out all ports.
Repeater Network – A network built with one or more
Repeater Hubs. Repeater networks share the same band-
width among all connected DTEs.
Sub-channel – Old term now called Audio Channel.
Switched Network – A network built with one or more
Switching Hubs. It is possible, even common to build a
network from a combination of interconnected Repeater
Hubs and Switched Hubs.
Switching Hub - A Switching Hub, or simply "Switch",
examines addressing fields on data arriving at each port
and attempts to direct the data out the port or ports to
which the data is addressed. Data may be buffered within
the Switching Hub to avoid the collision condition experi-
enced within a Repeater Hub. A network utilizing Switch-
ing Hubs realizes higher overall bandwidth capacity since
data may be received through multiple ports simulta-
neously without conflict.
Unicast – See Unicast addressing.
Unicast addressing – Data which is unicast is addressed to a
specific network device. A switching hub examines the
unicast address field of the data and determines on which
port the addressed device resides and directs the data out
only that port. Delivery of an email message is an example
of unicast data addressing.
