[LARTC] AF

["Tzeh Yeu Leang" <ltyvjc@hotmail.com>]

Hi all,

   Currently, I am experimenting with the example script afcbq and i have 
some problem here. Any helps is greatly appreciated. Here are part of my 
scripts (i didn't show the setup for AF class 2,3 and 4, but they are 
similar to setup of class 1):

# --- General setup  ---
tc qdisc add dev eth1 handle 1:0 root dsmark indices 64 set_tc_index
tc filter add dev eth1 parent 1:0 protocol ip prio 1 tcindex mask 0xfc shift 
2 pass_on
tc qdisc add dev eth1 parent 1:0 handle 2:0 cbq bandwidth 10Mbit cell 8 
avpkt 1000 mpu 64
tc filter add dev eth1 parent 2:0 protocol ip prio 1 tcindex mask 0xf0 shift 
4 pass_on

# --- AF Class 1 specific setup---
tc class add dev eth1 parent 2:0 classid 2:1 cbq bandwidth 10Mbit rate 2Mbit 
avpkt 1000 prio 1 bounded allot 1514 weight 1 maxburst 21
tc filter add dev eth1 parent 2:0 protocol ip prio 1 handle 1 tcindex 
classid 2:1
tc qdisc add dev eth1 parent 2:1 gred setup DPs 3 default 2

# --- AF Class 1 DP 1---
tc filter add dev eth1 parent 1:0 protocol ip prio 1 handle 10 tcindex 
classid 1:111
tc qdisc change dev eth1 parent 2:1 gred limit 60KB min 15KB max 45KB burst 
20 avpkt 1000 bandwidth 10Mbit DP 1 \
probability 0.02 prio 2

# --- AF Class 1 DP 2---
tc filter add dev eth1 parent 1:0 protocol ip prio 1 handle 12 tcindex 
classid 1:112
tc qdisc change dev eth1 parent 2:1 gred limit 60KB min 15KB max 45KB burst 
20 avpkt 1000 bandwidth 10Mbit DP 2 \
probability 0.04 prio 3

# --- AF Class 1 DP 3---
tc filter add dev eth1 parent 1:0 protocol ip prio 1 handle 14 tcindex 
classid 1:113
tc qdisc change dev eth1 parent 2:1 gred limit 60KB min 15KB max 45KB burst 
20 avpkt 1000 bandwidth 10Mbit DP 3 \
probability 0.06 prio 4

#------BE Queue setup------
tc filter add dev eth1 parent 1:0 protocol ip prio 2 handle 0 tcindex mask 0 
classid 1:1
tc class add dev eth1 parent 2:0 classid 2:5 cbq bandwidth 100Mbit rate 
2Mbit avpkt 1000 prio 8 bounded allot 1514 weight 1 maxburst 21
tc filter add dev eth1 parent 2:0 protocol ip prio 1 handle 0 tcindex 
classid 2:5
tc qdisc add dev eth1 parent 2:5 red limit 60KB min 15KB max 45KB burst 20 
avpkt 1000 bandwidth 10Mbit probability 0.4

##########################
Here are part of what i get when i "tc -s qdisc":
qdisc red 8005: dev eth1 limit 60Kb min 15Kb max 45Kb
Sent 0 bytes 0 pkts (dropped 0, overlimits 0)
  marked 0 early 0qdisc gred 8001: dev eth1
DP:1 (prio 8) Average Queue 0b Measured Queue 0b
	 Packet drops: 0 (forced 0 early 0)
	 Packet totals: 0 (bytes 0)  ewma 3 Plog 21 Scell_log 9
DP:2 (prio 8) Average Queue 0b Measured Queue 0b
	 Packet drops: 0 (forced 0 early 0)
	 Packet totals: 0 (bytes 0)  ewma 3 Plog 20 Scell_log 9
DP:3 (prio 8) Average Queue 0b Measured Queue 0b
	 Packet drops: 0 (forced 0 early 0)
	 Packet totals: 0 (bytes 0)  ewma 3 Plog 19 Scell_log 9
Sent 0 bytes 0 pkts (dropped 0, overlimits 0)

qdisc cbq 2: dev eth1 rate 10Mbit (bounded,isolated) prio no-transmit
Sent 0 bytes 0 pkts (dropped 0, overlimits 0)
  borrowed 0 overactions 0 avgidle 624 undertime 0

qdisc dsmark 1: dev eth1 indices 0x0040 set_tc_index
Sent 0 bytes 0 pkts (dropped 0, overlimits 0)
pdrop 0 other 0

#####################

my question is why is the prio shown is always 8, although i set them to 
prio 2,3,4 respectively? And i suspect because of this, i actually get 
better performance for BE (in terms of lower delay).

Also, i would like to clarify some requirement for af as proosed in RFC. In 
"Appendix: Example services" of RFC 2597, it said that AF1x should have 
"greater probability for timely forwarding by having lighter load". 
Therefore, i send lighter traffic to class 1, than class 2 and 3. But still 
i get lower delay for class BE, and no observable difference in delay for 
class 1, 2 and 3 (maybe it is the prio 8 problem as described above).

What do you guys think about the delay for AF as proposed in RFC? Should AF 
class 1 has the smallest delay compared to class 2,3 4 and BE?

Last question, what do we do with excess AF traffic? Do we drop it or 
downgrade it to BE?

If you have read to this part, i must thank you for your patience.




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