IEEE 802.1D and 802.1Q

IEEE’s 802.1Q standard defines a tag that can be added to voice and data packets. Most of the information associated with this tag deals with Virtual LAN (VLAN) management, but 3 bits are reserved for identifying packet priority. These 3 bits allow any one of 8 priorities to be assigned to a specific packet. As defined in the standard, the 8 priorities are, from highest to lowest:

• 7: Network management traffic
• 6: Voice traffic with less than 10ms latency
• 5: Voice traffic with less than 100ms latency
• 4: “Controlled-load” traffic for mission-critical data applications
• 3: Traffic meriting “extra-effort” by the network for prompt delivery, for example, executives’ e-mail
• 2: Reserved for future use
• 0: Traffic meriting the network’s “best-effort” for prompt delivery. This is the default priority.
• 1: Background traffic such as bulk data transfers and backups

NOTE: Priority 0 is a higher priority than Priority 1.

To support IEEE 802.1D/Q, the 4600 Series IP Telephones can be administered either of
two ways:

• from the network by appropriate administration of the DHCP or TFTP/HTTP servers, as covered in 4600 Series IP Telephone Scripts and Application Files, or
• at the telephone itself using dialpad input, as covered under local administrative procedures in the 4600 Series IP Telephone Installation Guide.

Eight IEEE 802.1D/Q QoS parameters in the telephones can be administered, as follows. The first five parameters are for standard 802.1Q tagging and apply to any 4600 Series IP Telephone. The last three parameters apply to all 4600 Series IP Telephones with a secondary Ethernet interface.

• L2Q: 802.1Q framing parameter (1=On, 2=Off, or 0=AUTO). The default is 0, but the preferred setting is 1 (ON). You can manually set the L2Q value of a specific 4600 IP Telephone to any value, for example, AUTO, ON, or OFF. However, any subsequent value administered via DHCP or TFTP/HTTP settings file will override the manual value. To use the QoS Local Administrative Option to set L2Q manually see the 4600 Series IP Telephone Installation Guide.
• L2QVLAN: the VLAN ID on which the telephone should operate. For example, what VLAN ID to use for DHCP Discovery, etc. (up to 4 digits, from 0 to 4094, default is 0).
• VLANTEST: the number of seconds to wait for a DHCPOFFER when using a non--zero VLAN ID (up to 3 digits, from 0 to 999, default is 60).
• L2QAUD: 802.1Q VoIP (voice) user RTP traffic priority value (between 0 and 7, default
  is 6).
• L2QSIG: 802.1Q VoIP (voice) user Call Control Signaling traffic priority value (between 0 and 7, default is 6).
• VLANSEP: enables VLAN separation when set to 1 (the default); disables VLAN separation when set to 0. If the value is zero, broadcasts are transmitted. Can only be administered using DHCP/TFTP, not by a manual procedure.
• PHY2VLAN: VLAN ID to be used for tagged (data) frames received on the secondary Ethernet interface when VLAN separation is enabled (up to 4 digits, from 0 to 4094, default is 0). Can only be administered using DHCP/TFTP, not by a manual procedure.
• PHY2PRIO: Layer 2 (data) priority value to be used for tagged frames received on
  the secondary Ethernet interface when VLAN separation is enabled (1 digit, 0 (zero) through 7, default is 0). Can only be administered using DHCP/TFTP, not by a manual procedure.

In the 4600 Series IP Telephone Installation Guide, the Local Administrative Option ADDR also allows you to specify VLAN IDs and VLANTEST values. The Local Administrative Option QoS allows you to specify values for L2Q, L2QAUD, and L2QSIG.

The 4600 Series IP Telephones can simultaneously support receipt of packets using, or not using, 802.1Q parameters.

For additional information on VLAN administration, see VLAN Considerations.