Cisco Systems IPMUX-1E operation manual ToS, UDP Destination Port

Chapter 4 Troubleshooting and Diagnostics IPmux-1/1EInstallation and Operation Manual

Question: How can I ensure the IPmux TDMoIP traffic priority over an IP Ethernet network?

Answer

The IPmux family is equipped with three different features that can be implemented in order to give the IPmux TDMoIP traffic priority 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 standards IEEE 802.1p&q. 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 enables configuring 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).

A configuration example:

Setting IP precedence of 101 and IP ToS of 1000 will give us the byte 10110000, which means that the IPmux IP-ToS parameter should be configured to 176 decimals.

UDP Destination Port

The IPmux uses the UDP protocol (Layer 4) in order to transfer the TDMoIP traffic. In the UDP protocol, the ¿ Destination port¿ field is always set to the decimal value

4-28 Frequently Asked Questions