Thossapron Apinyapanha wrote:
1. HFSC have 4 curve such sc, rc, ls, ul and
1.1 In leaf class can specify rc for guarantee service (bandwidth and delay)
and If want to sharing fairness exceess service, we must specify ls and ul curve too
(ls curve with paramater m2 specify at lease sharing bandwidth in that class will receive and
ul curve mean maximum bandwidth in that class will receive)
so i'm doubt .. about if i specify sc curve in leaf class too, what 's it mean??
rc, ls, ul + sc -> what's it mean?
rc + sc -> what's it mean?
On leaf sc = rt + ls ie. rt upto it's limit but able to go higher if
there is spare bandwidth to borrow with no rt guarentees.
On inner classes I guess sc is the same as ls.
In interior class can't specify rc curve but we can specify ls curve for doing link-sharing criterion
and can sharing fairness excess service too.
but so if i specify sc curve in leaf class too, what 's it mean?? like
how different if i specify "ls, ul and sc" and "ls, ul"???
In root class, what is it mean if i specify
sc -> what's it mean?
ls +ul -> what's it mean?
1.2 so can i conclude ls, ul, rc are subset 's sc curve.
and in each curve we can calculate banwidth and delay bound .?????
because all 4 curve have same parameter such m1 ,d , m2
2. i read a lot of HFSC paper about paramter (m1,d,m2)
some paper tell me ... d is interval time
(first will sending with m1 rate but after interval d parameter, it will change
rate to m2)
but some paper tell me .. d is delay bound in that class
(first will sending with m1 rate but when after exceed delay bound,
it will change rate to m2)
what 's it true??
Look at the picture on p10 of sigcom paper - I think d in (m1,d,m2) is x
which is either the same as d max or different depending on the shape of
the curve. Linux HFSC will convert (umax, dmax, rate) to (m1,d,m2).
2.1 if d are interval time so how HFSC calculate delay?
2.2 Is it true? -> "delay bound calculation from service curve"
3. this is my big problem with HFSC thoery ...
in HFSC has 2 criterion such real time and link-sharing criterion
so when packet coming in traffic control linux box
hfsc will checking eligible time in each packege
If eligible time < t
(i'm don't understand how eligble working or how it classify eligible package or not?)
or it's package that dangerouse for exceed deadline time
so it manage package with "real time criterion" and choosing
package with lowest deadline time for dequeue
but if it's not, it will manage with "link sharing criterion"
and choosing package with lowest vertual time
(this is a big don't unstand why choose lowest vertual time?
because it's mean class with have lowest will choose to dequeue
and what about another class that vertual time are now low??
how it can manage???
and i don't understand why must choose lowest not max vertual time?
Is it relative with fairness excess service all class?
I guess time moves on so vt on classes gets lower.
4. my lab... i found bandwidth allocation by HFSC
comparation with HTB ... found
At first time that class starting up, HFSC will receive banwidth nearly
upperlimit rate nomatter in that time have a lot class active????
(it's like can send with burst rate in HTB)
so comparation with HTB,
At first time that class starting up, HTB receive bandwidth not peak like
burst but it use interval time for increase bandwidth until start with rate and then with ceil.
Hmm, for how long (bytes) does that burst happen with hfsc, what rates?
I know emperically that rt classes are sort of work conserving in the
Linux (and BSD?) implementations. The algorithm in the paper is
different and more non work conserving as I see it.
5. i read a lot of HTB 's tc command case, with try to test burst situation ,
i don't know why burst parameter their specify not much like 12kbit
(but rate and ceil rate are so different from 12kbit such 200kbit
so i will follow them,, but after plot graph .... i don't see burst characteristic
at first time class active ...
Is i'm wrong to use burst paramter value 12 kbit???? it's too small?????
are
Burst is a buffer size so 12kbit=1.5kB slightly less than a 1500 byte
packet if shaping on eth (IPlen +14). Also the max rate of a backlogged
class is burst * Hz. On slow links setting burst < pktlen/low doesn't hurt.
Andy.
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