Filter
Top Products
6-148
Configuring the Switch
Class of Service (CoS): Managing Bandwidth More Effectively
Configuring the Switch
Packet Enters Switch: In an Untagged VLAN
Packet Exits From Switch: In a tagged VLAN
(Prioritizing affects both the choice of outbound priority queue and the packet’s 802.1p priority tag.)
In this scenario, the outbound packet always carries a tagged VLAN field with an 802.1p priority setting.
1. Device Priority (IP Address) Option
(IP Packets Only)
:
– If Device Priority does not apply to the packet, then packet priority defers to the ToS policy.
– If Device Priority (0 - 7) is configured and applies to a packet, then the packet is assigned to the appropriate queue
(high or normal priority) of the outbound port and the priority value is configured in the 802.1p priority tag in the
packet’s tagged VLAN field.
2. Type of Service (ToS) Option
(IP Packets Only)
:
– If ToS option is configured to Disabled, then packet priority defers to the Protocol Priority policy.
– IP Precedence option: Prioritizes packet (high or normal) according to the value of the ToS precedence bits (upper
three bits of ToS field; 0 - 7); 4 - 7 = high, 0 - 3 = normal. Also, the Precedence bits are used as follows to configure
the 802.1p priority tag in the packet’s tagged VLAN field:
–Differentiated Services option: Prioritizes packet (high or normal) according to Priority you set (0 - 7) for the packet’s
ToS field codepoint. Also, the 802.1p priority tag in the packet’s tagged VLAN field is configured to the same value
as the Priority you set for the ToS field codepoint. If Priority is set to No override (the default), then packet priority
defers to the Protocol Priority policy.
See “Using Type of Service (ToS) Criteria to Prioritize IP Traffic” on 6-143.
3. Protocol Priority Option:
– If Protocol Priority does not assign a priority to the packet, then packet priority defers to the VLAN ID policy.
– If Protocol Priority assigns a priority (0 - 7) to a packet, the packet is assigned to the appropriate queue (high or
normal priority) of the outbound port and the priority value is configured in the 802.1p priority tag in the packet’s
tagged VLAN field.
4. VLAN Priority Option:
– If VLAN Priority does not assign a priority to the packet, then the packet goes to the “normal” priority queue of an
outbound port.
– If VLAN Priority assigns a priority (0 - 7) to a packet, the packet is assigned to the appropriate queue (high or normal
priority) of the outbound port and the priority value is configured in the 802.1p priority tag in the packet’s tagged
VLAN field.
0
1
1
2
2
0
3
3
4
4
5
5
6
6
*To interpret these settings, see Table 6-6. Mapping Priority
Settings to Device Queues on page 6-133.
7
7
IP Precedence Setting:
802.1p Priority Setting*: