Installation and Operation Manual Chapter 6 Troubleshooting and Diagnostics
IPmux-11 Ver. 2.00 Frequently Asked Questions 6-23
Framed mode:
In case of local failure on the IPmux, or situation of jitter buffer
underflow/overflow, a conditioning pattern (00 to FF) will be sent towards the
near-end TDM device on the timeslots related to that specific bundle. A user-
configurable conditioning pattern can also be applied on the ABCD bits (CAS
signaling 1 to F), going towards the local TDM device.
In this case the synch on the E1/T1 level is maintained in favor of the TDM end
devices.
Q: How can I ensure the IPmux TDMoIP traffic priority over an IP
Ethernet network?
A: The IPmux units offer three different methods of the TDMoIP traffic
prioritization over an IP/Ethernet network:
VLAN ID (Layer 2)
ToS field (Layer 3)
UDP destination port (Layer 4).
Each QoS feature is based on a different OSI level and can be used individually
in order to ensure the TDMoIP traffic priority. When determining which feature
to use, it is important to verify that the different elements on the network,
(Switches / Routers / etc.), support the selected priority mechanism and are also
configured to give the highest priority to the labeled IPmux traffic.
Notice that the priority is given to the TDMoIP traffic by the network elements
and the IPmux is merely tagging the packets.
VLAN ID
The IPmux complies with the IEEE 802.1p&Q standards. This enables the user
to set both VLAN ID and VLAN Priority. It adds four bytes to the MAC layer
(Layer 2) of the Ethernet frame. These bytes contain information about the
VLAN ID, and the VLAN priority, which runs from 0–7. The IPmux only tags the
packets, while the switches are responsible for giving the priority according to
the VLAN info. Verify that the IPmux traffic has the highest priority in the
relevant Ethernet network.
ToS
There are several RFCs (RFC791, RFC1349, RFC2474) that define how the IP
ToS should be configured. The ToS is a byte located in the IP header (Layer 3).
In general the Type of Service octet, in most cases, consists of three fields:
The first field, labeled "PRECEDENCE", is intended to denote the importance or
priority of the datagram.
The second field, labeled "TOS", denotes how the network should make
tradeoffs between throughput, delay, reliability, and cost.
The last field, labeled "MBZ" (for "must be zero") above, is currently unused.
The IPmux can configure the whole IP ToS byte, and therefore it is adaptable to
each RFC in the market. The IP ToS parameter in the IPmux is user-configured
in terms of decimal value. However, on the frame itself it of course appears in
binary format. The decimal value varies between 0 and 255 (8 bits).