Cisco Systems IPMUX-1E operation manual Packet Delay Variation, Vlan Support, UDP Support

Chapter 1 Introduction IPmux-1/1EInstallation and Operation Manual

VLAN Support

VLAN, according to IEEE 802.1p&q, adds four bytes to the MAC layer of the Ethernet frame. The user can set the contents of these bytes, MAC layer priority and VLAN ID. In this mode, only VLAN format frames are sent and received by IPmux-1. Figure 1-16shows the VLAN tag format.

81 00

802.1D Tag Protocol Type

user_priority		0				VID
		CFI =
8	6	5	4	1	8	1
	Priority					VLAN ID

Figure 1-16. VLAN Tag Format (802.1p&q)

UDP Support

Table 1-3. UDP Ports Definition

Field Length (Bits)	Field Description	Value	Function
2 bytes	UDP Source Port	2–497d*	Destination timeslots bundle
2 bytes	UDP Destination Port	2142d	Standard TDMoIP UDP port

	* The MSB of this field can be either 1 or 0 for inband end-to-end proprietary signaling.
Note
	The UDP Source Port field is used for destination timeslots bundle indication.
	For example, if the destination is:
	Bundle 1 – 02, Bundle 2 – 03, Bundle 3 – 04, Bundle 4 – 05, etc.

For more information about VLAN tagging, refer to IEEE Standard 802.1p&q.

Packet Delay Variation

Packets are transmitted at set intervals. Packet Delay Variation is the maximum deviation from the nominal time the packets are expected to arrive at the far end device. IPmux-1 has a buffer that compensates for the deviation from the expected packet arrival time to prevent IPmux-1 buffers from emptying out or overflowing.

Packet Delay Variation is an important network parameter. Large PDV (exceeding the jitter buffer configuration) will cause receive buffer underflows and errors at the TDM level (see Figure 1-17).

To compensate for large PDV, configure the PDVT (jitter) buffer to a higher value.

1-18 Functional Description