Terminology:
AF – Assured forwarding
EF – Expedite Forwarding
BE – Best Effort
CS – Class Selector – use for backward compatibility with IP Precedence.
MPD – Mark Probability Denominator.
FIFO – First-In-First-Out
The number on the bracket ( x ) is the decimal equivalence of the AF or CS value.
Typical Classification Table:
Class-Map Value
AF1x: ip dscp cs1 ( 8 ) af11 (10) af12 (12) af13 (14)
AF2x: ip dscp cs2 (16) af21 ( 18 ) af22 (20) af23 (22)
AF3x: ip dscp cs3 (24) af31 (26) af32 ( 28 ) af33 (30)
AF4x: ip dscp cs4 (32) af41 (34) af42 (36) af43 ( 38 )
EF/Prec 5: ip dscp cs5 (40) ef (46)
You don’t need for memorize the conversion of AFx / CSx value to its decimal equivalent. There is a formula on how it arrived. Let’s do some basic math.
Formula for AF:
Given: AFxy
Let x = first digit [1 -4 ]
Let y = second digit [1 -3]
Decimal Value = 8x +2y
Formula for CS = 8y
EF = always = 46.
Sample:
AF43 : x=4 , 3=y;
Decimal Value = 8x +2y
Decimal Value = 8(4) + 2(3)
Decimal Value = 32 + 6
Decimal Value = 38
Sample 2:
CS1 = 8y = 8
CS2 = 8(2) = 16
How get the value to be used for the extended ping test:
Examples:
Decimal Value = 38 = 100110 in binary
Then 100110 + “00” = 10011000
10011000 convert back to decimal becomes 152.
Decimal Value = 46 = 101110 binary
Then 101110 + “00” = 10111000
10111000 convert back to decimal becomes 184.
1. Once you get the decimal value, open your scientific calculator (windows – calc.exe will do )
2. Input the decimal value, convert to binary, then add two zeros “00”
3. Convert back to decimal. Here you get the actually value to be used for you extended ping test.
Based on our classification above we use 5 queue only to make classification not to complicated. Let call the the “ETM” Enhanced Traffic Marking.
Also per bucket or class we do WRED (weighted random early detection) based on DSCP. Also configured with MPD = 1, means 100 drop rate once the maximum threshold is reach.
In the ERA of MPLS, a mere packet loss on our ping test does not give a direct conclusion of a dirty line or circuit. We should always check each QoS queue and see if this taking violations, remarked or even drops.
You can use this command in looking for the values you need.
show policy-map interface [Interface-Name] output | i op|ass|ark|form|iola
show policy-map interface [Interface-Name] input | | i op|ass|ark|form|iola
On this case you can see a Qos in action. As you can follow logs below, we did a ping test on the EF queue (Decimal 184) and we see a packet drops. This is because the output queue is already congested.
While pinging at BE marked ping packets (0) value we see a vey clean sweet ping results.
This will conclude that the issue is not on the circuit, meaning , ckt must be error free and clean. The problem is the congestion of traffic class. Btw, within a class scheduling used is FIFO.
Router Logs:
Ping test using BE:
MPLS-Router-1>ping vrf VPN-CustomerA 19.25.19.25 repeat 1000 size 1400
Type escape sequence to abort.
Sending 1000, 1400-byte ICMP Echos to 19.25.19.25, timeout is 2 seconds:
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Snip…
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!
Success rate is 100 percent (1000/1000), round-trip min/avg/max = 1/2/24 ms
Ping test using EF Queue:
MPLS-Router-1>ping vrf VPN-CustomerA
Protocol [ip]:
Target IP address: 19.25.19.25
Repeat count [5]: 1000
Datagram size [100]: 1400 <<<<<<<<<<<<<<<- Large packet size
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface:
Type of service [0]: 184 <<<<<<<<<<<<<<<- EF- Marked ICMP Packet
Set DF bit in IP header? [no]:
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 1000, 1400-byte ICMP Echos to 19.25.19.25, timeout is 2 seconds:
!!!!!!.!!!!.!!!!.!!!!.!!!.!!!.!!!.!!!.!!!.!!!.!!!.!!!.!!!.!!!.!!!.!!!.
Snip….
!!.!!!!.!!!!.!!!!.!!!!.!!!!.!!!.!!!.!!!.!!!.!!!.!!!.!!!.!!!.!!!.!!!.!!
Success rate is 76 percent (769/1000), round-trip min/avg/max = 1/1/224 ms
MPLS-Router-1>ping vrf VPN-CustomerA
Protocol [ip]:
Target IP address: 19.25.19.25
Repeat count [5]: 1000
Datagram size [100]: 1400
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface:
Type of service [0]: 136 <<<<<<<<<<<<- af41 (34) marked ICMP
Set DF bit in IP header? [no]:
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 1000, 1400-byte ICMP Echos to 19.25.19.25, timeout is 2 seconds:
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
Snip….
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
!!!!!!!!!!!!!!!!!!!!
Success rate is 100 percent (1000/1000), round-trip min/avg/max = 1/2/20 ms
MPLS-Router-1>
Input Policy is clean, no drops on the EF queue.
MPLS-Router-1>sh policy-map interface Serial1/0/0.20892 in
Serial1/0/0.20892
Service-policy input: INPUT-POLICY
Class-map: EF(match-any)
26677343 packets, 1708347477 bytes
5 minute offered rate 68000 bps, drop rate 0 bps
Match: ip dscp cs5 (40) ef (46)
26677343 packets, 1708347477 bytes
5 minute rate 68000 bps
Police:
256000 bps, 32000 limit, 32000 extended limit
conformed 26676976 packets, 1708323989 bytes; action: set-mpls-exp-transmit 5
exceeded 0 packets, 0 bytes; action: set-mpls-exp-transmit 5
violated 0 packets, 0 bytes; action: drop
Class-map: AF4x(match-any)
4744649 packets, 2171531130 bytes
5 minute offered rate 4000 bps, drop rate 0 bps
Match: ip dscp cs4 (32) af41 (34) af42 (36) af43 (38)
4744649 packets, 2171531130 bytes
5 minute rate 4000 bps
QoS Set
mpls experimental imposition 4
Packets marked 4744649
Class-map: AF3x(match-any)
28039 packets, 5503914 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip dscp cs3 (24) af31 (26) af32 (28) af33 (30)
11407 packets, 4611124 bytes
5 minute rate 0 bps
Match: ip dscp cs6 (48) cs7 (56)
16632 packets, 892790 bytes
5 minute rate 0 bps
QoS Set
mpls experimental imposition 3
Packets marked 28039
Class-map: AF2x(match-any)
2664905 packets, 867531648 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip dscp cs2 (16) af21 (18) af22 (20) af23 (22)
2664905 packets, 867531648 bytes
5 minute rate 0 bps
QoS Set
mpls experimental imposition 2
Packets marked 2664905
Class-map: BE(match-any)
1473520 packets, 219300011 bytes
5 minute offered rate 3000 bps, drop rate 0 bps
Match: ip precedence 0 1 2 3
1473520 packets, 219300011 bytes
5 minute rate 3000 bps
Match: ip precedence 4 5 6 7
0 packets, 0 bytes
5 minute rate 0 bps
QoS Set
mpls experimental imposition 0
Packets marked 1473520
Class-map: class-default (match-any)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
0 packets, 0 bytes
5 minute rate 0 bps
MPLS-Router-1>sh policy-map interface Serial1/0/0.20892 out
Serial1/0/0.20892
Service-policy output: NESTED-PE-CE-6K
Class-map: class-default (match-any)
36751759 packets, 8673566210 bytes
5 minute offered rate 155000 bps, drop rate 0 bps
Match: any
0 packets, 0 bytes
5 minute rate 0 bps
Output queue: 0/128; 0/0 packets/bytes output, 0/0 drops
Shape : 6092 kbps
Service-policy : OUT-POLICY
Class-map: EF(match-any)
26002327 packets, 1665771828 bytes
5 minute offered rate 68000 bps, drop rate 0 bps
Match: ip dscp cs5 (40) ef (46)
26002327 packets, 1665771828 bytes
5 minute rate 68000 bps
Output queue: 0/256; 26002327/1665723508 packets/bytes output, 0/0 drops
Absolute priority
Police:
3048000 bps, 9525 limit, 0 extended limit
conformed 26001319 packets, 1665666996 bytes; action: transmit
exceeded 0 packets, 0 bytes; action: transmit
violated 29 packets, 42176 bytes; action: drop
Class-map: AF4x(match-any)
3748257 packets, 2208700671 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip dscp cs4 (32) af41 (34) af42 (36) af43 (38)
3748257 packets, 2208700671 bytes
5 minute rate 0 bps
Output queue: 0/1024; 3735280/2190803028 packets/bytes output, 12977/17941551 drops
Bandwidth : (Weight 40)
Random-detect (DSCP-based):
Exponential weight: 9 (1/512)
Current average queue length: 0 packets
———————————————————————–
Diff-Serv Min Max Mark Rand-Drop Tail-Drop
codepoint thres thres probability Pkts Bytes Pkts Bytes
———————————————————————–
32 171 500 1/1 0 0 0 0
34 171 500 1/1 0 0 0 0
36 52 171 1/1 12977 17941551 0 0
38 52 171 1/1 0 0 0 0
Default 256 512 1/10 0 0 0 0
Class-map: AF3x(match-any)
2107826 packets, 1588258194 bytes
5 minute offered rate 92000 bps, drop rate 0 bps
Match: ip dscp cs3 (24) af31 (26) af32 (28) af33 (30)
2090633 packets, 1587146544 bytes
5 minute rate 92000 bps
Match: ip dscp cs6 (48) cs7 (56)
17193 packets, 1111650 bytes
5 minute rate 0 bps
Output queue: 0/1024; 2107827/1588123702 packets/bytes output, 0/0 drops
Bandwidth : (Weight 39)
Random-detect (DSCP-based):
Exponential weight: 9 (1/512)
Current average queue length: 0 packets
———————————————————————–
Diff-Serv Min Max Mark Rand-Drop Tail-Drop
codepoint thres thres probability Pkts Bytes Pkts Bytes
———————————————————————–
24 250 500 1/1 0 0 0 0
26 250 500 1/1 0 0 0 0
28 52 250 1/1 0 0 0 0
30 52 250 1/1 0 0 0 0
48 511 512 1/10 0 0 0 0
56 511 512 1/10 0 0 0 0
Default 256 512 1/10 0 0 0 0
Class-map: AF2x(match-any)
1599388 packets, 1526755319 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip dscp cs2 (16) af21 (18) af22 (20) af23 (22)
1599388 packets, 1526755319 bytes
5 minute rate 0 bps
Output queue: 0/1024; 1599343/1526694011 packets/bytes output, 45/61488 drops
Bandwidth : (Weight 16)
Random-detect (DSCP-based):
Exponential weight: 9 (1/512)
Current average queue length: 0 packets
———————————————————————–
Diff-Serv Min Max Mark Rand-Drop Tail-Drop
codepoint thres thres probability Pkts Bytes Pkts Bytes
———————————————————————–
18 171 500 1/1 0 0 0 0
20 52 171 1/1 0 0 0 0
22 52 171 1/1 45 61488 0 0
Default 171 500 1/1 0 0 0 0
Class-map: dscp_AF1x_ipprec_1_6Qs (match-any)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip dscp cs1 (8) af11 (10) af12 (12) af13 (14)
0 packets, 0 bytes
5 minute rate 0 bps
Output queue: 0/1024; 0/0 packets/bytes output, 0/0 drops
Bandwidth : (Weight 1)
Random-detect (DSCP-based):
Exponential weight: 9 (1/512)
Current average queue length: 0 packets
———————————————————————–
Diff-Serv Min Max Mark Rand-Drop Tail-Drop
codepoint thres thres probability Pkts Bytes Pkts Bytes
———————————————————————–
10 171 500 1/1 0 0 0 0
12 52 171 1/1 0 0 0 0
14 52 171 1/1 0 0 0 0
Default 171 500 1/1 0 0 0 0
Class-map: BE(match-any)
3293961 packets, 1684080198 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: ip precedence 0 1 2 3
3293961 packets, 1684080198 bytes
5 minute rate 0 bps
Match: ip precedence 4 5 6 7
0 packets, 0 bytes
5 minute rate 0 bps
Output queue: 0/1024; 3293710/1683786046 packets/bytes output, 251/286996 drops
Bandwidth : (Weight 4)
Random-detect (DSCP-based):
Exponential weight: 9 (1/512)
Current average queue length: 0 packets
———————————————————————–
Diff-Serv Min Max Mark Rand-Drop Tail-Drop
codepoint thres thres probability Pkts Bytes Pkts Bytes
———————————————————————–
Default 171 500 1/1 251 286996 0 0
Class-map: class-default (match-any)
0 packets, 0 bytes
5 minute offered rate 0 bps, drop rate 0 bps
Match: any
0 packets, 0 bytes
5 minute rate 0 bps
Output queue: 0/128; 0/0 packets/bytes output, 0/0 drops
MPLS-Router-1> end
