Telos Zephyr Xstream User Manual page 302

Condition: Able to connect and lock to a distant site using IP, but audio dropouts
occur frequently
Do local LAN connections work ok (or with a greatly reduced number of dropouts?
Increasing the buffer setting may help. Also note that the Xstream has error
concealment technology when using AAC, so we recommend using that protocol for this
reason.
Try increasing the buffer size in the CODEC menu
What QOS (Quality of Service) mechanism is in place on the IP path between the two sites?
Such QOS control is currently impossible if the path includes the public Internet. QOS
options on a private network are limited. If no other equipment is sharing the IP link,
then QOS is a non‐issue. As soon as other equipment shares the link, it has the ability to
use all bandwidth at times it needs it (when downloading or transferring a file, for
example).
Your network equipment and IP link service provider may be able to assist with
strategies. A qualified Information Technologist will be invaluable.
One crude strategy, when only a few devices will share the link, is to use the Ethernet
port to limit bandwidth. For example, if your primary point‐to‐point link is at 100 Mbps
(mega bits per second), and it is fed from a single Ethernet hub using an Ethernet 100
Base‐T (100 megabit) hub you could connect a limited number of 10 Base‐T (10 megabit)
devices. In this case you should be able to use eight to nine 10 Base‐T devices. These
devices must not use 100 Base‐T or they can swamp the 100 megabit connection.
The same setup could be used with smaller number of 10 Base‐T connections if the link
were at a lower rate (i.e. you could connect three 10 Base‐T devices if the link were 50
Mbps).
Unfortunately, the usual case is that the point‐to‐point link is at a rate much lower than
10 mbps ‐ often, 2.048 or 1.544 kbps (kilobits per second) or less. In this case, the
simple strategy above cannot be used.
Another problem with IP delivery is "packet loss". Most IP providers do not guarantee a
specific degree of packet loss. Note that there are some exceptions. In particular,
MPLS‐based services often provide more than one "class of service" or priority level
which can allow the system designer to protect bandwidth for critical operations such as
codecs.
What is the "packet loss" of the IP path?
Does the problem disappear if other devices are removed from the IP network (i.e. does it work if
the IP network is not shared on either end)?
Condition: Unable to connect in IP streaming modes.
Your firewall and router may not be permitting the IP streams to pass to the Xstream. You may
need to use port forwarding to pass the audio packets to the Xstream. At the minimum you
must open the UDP port (default is 9150).
Section 13: Deep Tech Information and Troubleshooting
USER'S MANUAL
290