Hello Deepak,
CoS Queue - When the incoming traffic reaches the device, it takes the action based on the configured BA or MF classifier/filter where the forwarding-class are defined. Both the Forwarding Class and Queues are relative. i.e. Queues are mapped to the Forwarding classes.
Example:Queue Forwarding-class
0 best-effort
1 expedited-forwarding
2 assured-forwarding
3 network-control
Please keep in mind that by default Queue 3 has the Highest priority and further it goes down to Queue 2, 1 and 0.
Queue Buffer - Each interface queue has its own Queue Buffer which is nothing but the size of the memory space that is allocated for storing the packets. You can view this buffer by using the command "
show interfaces queue".
Example:
Reserved buffer - The size of the memory buffer that is allocated for storing packets
Current - The amount of buffer memory that is currently in use on this queue.
Current - The maximum number of bytes in this queue, that is currently in use on this queue.
user@host> show interfaces queue
Physical interface: ge-0/0/0, Enabled, Physical link is Up
Interface index: 135, SNMP ifIndex: 510
Forwarding classes: 8 supported, 4 in use
Egress queues: 8 supported, 4 in use
Queue: 0, Forwarding classes: best-effort
Queued:
Packets : 14686 0 pps
Bytes : 616812 0 bps
Transmitted:
Packets : 14686 0 pps
Bytes : 616812 0 bps
Tail-dropped packets : 0 0 pps
RL-dropped packets : 0 0 pps
RL-dropped bytes : 0 0 bps
RED-dropped packets : 0 0 pps
Low : 0 0 pps
Medium-low : 0 0 pps
Medium-high : 0 0 pps
High : 0 0 pps
RED-dropped bytes : 0 0 bps
Low : 0 0 bps
Medium-low : 0 0 bps
Medium-high : 0 0 bps
High : 0 0 bps
Queue Buffer Usage:Reserved buffer : 118750000 bytesQueue-depth bytes :Current : 0
Queue: 1, Forwarding classes: expedited-forwarding
Queued:
Packets : 0 0 pps
Bytes : 0 0 bps
Transmitted:
Packets : 0 0 pps
Bytes : 0 0 bps
Tail-dropped packets : 0 0 pps
RL-dropped packets : 0 0 pps
RL-dropped bytes : 0 0 bps
RED-dropped packets : 0 0 pps
Low : 0 0 pps
Medium-low : 0 0 pps
Medium-high : 0 0 pps
High : 0 0 pps
RED-dropped bytes : 0 0 bps
Low : 0 0 bps
Medium-low : 0 0 bps
Medium-high : 0 0 bps
High : 0 0 bps
Queue Buffer Usage:Reserved buffer : 9192 bytesQueue-depth bytes :Current : 0
Queue: 2, Forwarding classes: assured-forwarding
Queued:
Packets : 0 0 pps
Bytes : 0 0 bps
Transmitted:
Packets : 0 0 pps
Bytes : 0 0 bps
Tail-dropped packets : 0 0 pps
RL-dropped packets : 0 0 pps
RL-dropped bytes : 0 0 bps
RED-dropped packets : 0 0 pps
Low : 0 0 pps
Medium-low : 0 0 pps
Medium-high : 0 0 pps
High : 0 0 pps
RED-dropped bytes : 0 0 bps
Low : 0 0 bps
Medium-low : 0 0 bps
Medium-high : 0 0 bps
High : 0 0 bps
Queue Buffer Usage:Reserved buffer : 9192 bytesQueue-depth bytes :Current : 0...
In a nut shell,
- Queues and Buffers are not the same.
- Each Queues has its own buffer.
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Original Message:
Sent: 04-02-2021 02:49
From: Unknown User
Subject: QoS: Is the queue and the buffer the same thing?
Hi.
While reading QoS, I come across the terms queue (eg. queue fill percentage) and buffer (eg. if a queue is out-of-profile, its packet is buffered).
Isn't the queue the same thing as the buffer?
If queue 0 is configured for a buffer size of say 100 bytes, doesn't that mean that the queue length is 100bytes and there is no separate 'buffer' that can store up to 100 bytes?
Or does each queue actually have a separate buffer such that there can be several notification cells both within the queue and also within the buffer assigned to that queue?
Thanks,
Deepak