What are LLQ (Low Latency Queuing) and CBWFQ (Class-Based Weighted Fair Queuing)? How to configure LLQ and CBWFQ?
LLQ (Low Latency Queuing)
CBWFQ (Class-Based Weighted Fair Queuing)
Cisco created CBWFQ and LLQ using some of the best concepts from legacy queuing methods. PQ and CQ as well as WFQ while adding several features.
LLQ low-latency queuing is developed by Cisco and it provides strict priority queuing to CBWFQ (class-based weighted fair queueing. Low-latency queuing provides delay-sensitive data like VoIP traffic to be given more preferential treatment over other traffic by letting the data be dequeued and sent first.
CBWFQ (Class-Based Weighted Fair Queuing) it’s a scheduling mechanism that allows a minimum bandwidth guarantee when the network congestion occurs on an interface.
CBWFQ is used to provide traffic classes during times of network congestion at an interface. Each of the CBWFQ queues is assigned a weight, and the packets are treated from the queues based upon the weight of the queue.CBWFQ and LLQ both support 64 queues/classes and also have one special queue called the class-default queue. LLQ and CBWFQ are both tools that use MQC and NBAR for configuration. there is one drawback in CBWFQ is VoIP traffic suffers an unacceptable delay.
Advantage of LLQ
LLQ provides all the benefits of CBWFQ (Class-Based Weighted Fair Queuing), including the capability of the user to queue and guarantees each queue an appropriate amount of bandwidth and to apply WRED to each of the queues (except to the strict-priority queue).
LLQ combines priority queuing and CBWFQ and provides Strict priority queueing for sensitive traffic like VoIP and video. LLQ also reduces latency/jitter for communications.
let’s see the configuration for a better understanding of LLQ and CBWFQ.
Topology:- https://qos.internetworks.in/2021/10/what-is-llq-low-latency-queuing-and.html
Goal:-
- configure the topology as per the diagram above.
- configure IP addresses to their ports
- configure EIGRP AS 65120 and advertise directly connected interfaces.
- configure CBWFQ tool on router 1
- configure ICMP bandwidth 18 percent, FTP bandwidth 28 and HTTP bandwidth 38.
- configure LLQ tool on router 3
- configure VoIP priority 192, ICMP bandwidth 120, HTTP priority 10 and FTP priority 15.
- The rest of the traffic use WFQ.
R1(config)#interface serial 4/0
R1(config-if)#ip address 192.168.10.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#exit
R1(config)#interface fastEthernet 0/0
R1(config-if)#ip address 10.1.1.1 255.255.255.0
R1(config-if)#no shutdown
R1(config-if)#no keepalive
R1(config-if)#exit
R2(config)#interface serial 4/0
R2(config-if)#ip address 192.168.10.2 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R2(config)#interface fastEthernet 0/0
R2(config-if)#ip address 20.1.1.1 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#no keepalive
R2(config-if)#exit
R2(config)#interface serial 4/1
R2(config-if)#ip address 23.1.1.1 255.255.255.0
R2(config-if)#no shutdown
R2(config-if)#exit
R3(config)#interface serial 4/1
R3(config-if)#ip address 23.1.1.2 255.255.255.0
R3(config-if)#no shutdown
R3(config-if)#exit
R3(config)#interface fastEthernet 0/0
R3(config-if)#ip address 30.1.1.1 255.255.255.0
R3(config-if)#no keepalive
R3(config-if)#no shutdown
R3(config-if)#exit
R1(config)#router eigrp 65120
R1(config-router)#network 192.168.10.0
R1(config-router)#network 10.0.0.0
R1(config-router)#no auto-summary
R1(config-router)#exit
R2(config)#router eigrp 65120
R2(config-router)#network 192.168.10.0
R2(config-router)#network 192.168.10.0
R2(config-router)#network 20.0.0.0
R2(config-router)#network 23.1.1.0
R2(config-router)#no auto-summary
R2(config-router)#exit
R3(config)#router eigrp 65120
R3(config-router)#network 23.1.1.0
R3(config-router)#network 30.0.0.0
R3(config-router)#no auto-summary
R3(config-router)#exit
R1(config)#class-map ICMP-TRAFFIC
R1(config-cmap)#match protocol icmp
R1(config-cmap)#class-map HTTP-TRAFFIC
R1(config-cmap)#match protocol http
R1(config-cmap)#class-map FTP-TRAFFIC
R1(config-cmap)#match protocol ftp
R1(config-cmap)#exit
R1(config)#policy-map CBWFQ-QUEUE
R1(config-pmap)#class ICMP-TRAFFIC
R1(config-pmap-c)#bandwidth percent 18
R1(config-pmap-c)#class HTTP-TRAFFIC
R1(config-pmap-c)#bandwidth percent 38
R1(config-pmap-c)#exit
R1(config-pmap)#policy-map CBWFQ-QUEUE
R1(config-pmap)#class FTP-TRAFFIC
R1(config-pmap-c)#bandwidth percent 28
R1(config-pmap-c)#exit
R1(config-pmap)#class class-default
R1(config-pmap-c)#exit
R1(config-pmap)#exit
R1(config)#interface serial 4/0
R1(config-if)#service-policy output CBWFQ-QUEUE
R1(config-if)#END
R1#show policy-map interface serial 4/0
Serial4/0
Service-policy output: CBWFQ-QUEUE
Class-map: ICMP-TRAFFIC (match-all)
0 packets, 0 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: protocol icmp
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
bandwidth 18% (277 kbps)
Class-map: HTTP-TRAFFIC (match-all)
0 packets, 0 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: protocol http
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
bandwidth 38% (586 kbps)
Class-map: FTP-TRAFFIC (match-all)
0 packets, 0 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: protocol ftp
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
bandwidth 28% (432 kbps)
Class-map: class-default (match-any)
2 packets, 48 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: any
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 2/48
R1#show run policy-map
Building configuration…
Current configuration : 185 bytes
!
policy-map CBWFQ-QUEUE
class ICMP-TRAFFIC
bandwidth percent 18
class HTTP-TRAFFIC
bandwidth percent 38
class FTP-TRAFFIC
bandwidth percent 28
class class-default
!
end
R1#show run class-map
Building configuration…
Current configuration : 168 bytes
!
class-map match-all FTP-TRAFFIC
match protocol ftp
class-map match-all ICMP-TRAFFIC
match protocol icmp
class-map match-all HTTP-TRAFFIC
match protocol http
end
FROM ROUTER 2
FROM ROUTER 1
- configure LLQ tool on router 3
R3(config)#ip access-list extended VoIP
R3(config-ext-nacl)#permit udp any any range 16380 32770
R3(config-ext-nacl)#exit
R3(config)#class-map ICMP-TRAFFIC
R3(config-cmap)#match protocol icmp
R3(config-cmap)#exit
R3(config)#class-map HTTP-TRAFFIC
R3(config-cmap)#match protocol http
R3(config-cmap)#exit
R3(config)#class-map FTP-TRAFFIC
R3(config-cmap)#match protocol ftp
R3(config-cmap)#exit
R3(config)#class-map VoIP-TRAFFIC
R3(config-cmap)#match access-group name VoIP
R3(config-cmap)#EXIT
R3(config)#policy-map LLQ
R3(config-pmap)#class VoIP-TRAFFIC
R3(config-pmap-c)#priority 190
R3(config-pmap-c)#exit
R3(config-pmap)#class ICMP-TRAFFIC
R3(config-pmap-c)#bandwidth 120
R3(config-pmap-c)#exit
R3(config-pmap)#class HTTP-TRAFFIC
R3(config-pmap-c)#priority 10
R3(config-pmap-c)#exit
R3(config-pmap)#class FTP-TRAFFIC
R3(config-pmap-c)#priority 15
R3(config-pmap-c)#exit
R3(config-pmap)#class class-default
R3(config-pmap-c)#fair-queue
R3(config-pmap-c)#exit
R3(config-pmap)#exit
R3(config)#interface serial 4/1
R3(config-if)#service-policy output LLQ
R3(config-if)#EXIT
R3(config)#END
R3#show policy-map interface serial 4/1
Serial4/1
Service-policy output: LLQ
queue stats for all priority classes:
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
Class-map: VoIP-TRAFFIC (match-all)
0 packets, 0 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: access-group name VoIP
Priority: 190 kbps, burst bytes 4750, b/w exceed drops: 0
Class-map: ICMP-TRAFFIC (match-all)
0 packets, 0 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: protocol icmp
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
bandwidth 120 kbps
Class-map: HTTP-TRAFFIC (match-all)
0 packets, 0 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: protocol http
Priority: 10 kbps, burst bytes 1500, b/w exceed drops: 0
Class-map: FTP-TRAFFIC (match-all)
0 packets, 0 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: protocol ftp
Priority: 15 kbps, burst bytes 1500, b/w exceed drops: 0
Class-map: class-default (match-any)
5 packets, 280 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: any
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops/flowdrops) 0/0/0/0
(pkts output/bytes output) 5/280
Fair-queue: per-flow queue limit 16 packets
R3#show policy-map
Policy Map LLQ
Class VoIP-TRAFFIC
priority 190 (kbps)
Class ICMP-TRAFFIC
bandwidth 120 (kbps)
Class HTTP-TRAFFIC
priority 10 (kbps)
Class FTP-TRAFFIC
priority 15 (kbps)
Class class-default
fair-queue
R3#show run class-map
Building configuration…
Current configuration : 231 bytes
!
class-map match-all FTP-TRAFFIC
match protocol ftp
class-map match-all VoIP-TRAFFIC
match access-group name VoIP
class-map match-all ICMP-TRAFFIC
match protocol icmp
class-map match-all HTTP-TRAFFIC
match protocol http
end
R3#show run policy-map
Building configuration…
Current configuration : 197 bytes
!
policy-map LLQ
class VoIP-TRAFFIC
priority 190
class ICMP-TRAFFIC
bandwidth 120
class HTTP-TRAFFIC
priority 10
class FTP-TRAFFIC
priority 15
class class-default
fair-queue
!
end
R3#ping 10.1.1.1 source 30.1.1.1 repeat 11
Type escape sequence to abort.
Sending 11, 100-byte ICMP Echos to 10.1.1.1, timeout is 2 seconds:
Packet sent with a source address of 30.1.1.1
!!!!!!!!!!!
Success rate is 100 percent (11/11), round-trip min/avg/max = 40/48/56 ms
R3#show policy-map interface serial 4/1
Serial4/1
Service-policy output: LLQ
queue stats for all priority classes:
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 0/0
Class-map: VoIP-TRAFFIC (match-all)
0 packets, 0 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: access-group name VoIP
Priority: 190 kbps, burst bytes 4750, b/w exceed drops: 0
Class-map: ICMP-TRAFFIC (match-all)
16 packets, 1664 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: protocol icmp
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops) 0/0/0
(pkts output/bytes output) 16/1664
bandwidth 120 kbps
Class-map: HTTP-TRAFFIC (match-all)
0 packets, 0 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: protocol http
Priority: 10 kbps, burst bytes 1500, b/w exceed drops: 0
Class-map: FTP-TRAFFIC (match-all)
0 packets, 0 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: protocol ftp
Priority: 15 kbps, burst bytes 1500, b/w exceed drops: 0
Class-map: class-default (match-any)
420 packets, 28159 bytes
5 minute offered rate 0000 bps, drop rate 0000 bps
Match: any
Queueing
queue limit 64 packets
(queue depth/total drops/no-buffer drops/flowdrops) 0/0/0/0
(pkts output/bytes output) 420/28159
Fair-queue: per-flow queue limit 16 packets
