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Good evening,

slide 60:
Why do we have [40,2] for the path 30->50->40?
Shouldn't we have [30,2]?

Posted by Raphaël Tagliani at 19:22
Comments (2)
===== 1.archi.pdf =====

----- slide 34, example:

first problem/question:

"S/N=signal noise ratio (not expressed in dB)" what is the meaning? We shouldn't use dBs?

second problem/question:

C_max = B*log_2(1+S/N) = 3000*log(1+30) = (~) 3000*log(2^5) = 3000*5 = 15kb/s
Am I wrong?

---- slide 39, stop&go solution:

packet P1 sent

Posted by Raphaël Tagliani at 17:50
Comments (3)
I'm not really sure that all of them are typos, but as they look strange to me, I put them here anyway...
The part between "" is taken from the slides and below, is the correction I propose.


"How: Define pk(i) as the cost of the best path from i to anywhere in at most k hops."
pk(i) is the attribute of a path, not its cost.

The top right link is labeled L14, but it should be L13.

"all bridges send a BPDU to neighbours every helloTimer ( = 2*2s = 4s)"
either a BPDU is send every helloTimer ( = 2s) or every 2 helloTimer( = 2*2s = 4s)


"Link A1-A2 fails, link X3-X6 is not in area 1."
It should be link X3-X5
"cannot pass to X5 a packet to A1 and to X3 a packet to A2"
should be from A1 and from A2 instead of to A1 and to A2

The figure lists routers A, C, F, F. It should be A, C, B, D

in area 1 topology database, the cost to n2 through the upper router is 34, not 22.


"Q2: describe the content of a packet from A to B visible at point 1."
There's no host B, but a server S.

"A2: contains an encrypted block of data inside a TCP packet with srce port=22, dest port=3456, IP srce=A, IP dest=S"
The port numbers are inverted., the src port on A is 3456 and the dest port is 22


"A: at 1 SA= DA=
at 2 SA=PREFIX:: DA=FEDC:BA98::7654:3210:"
1 and 2 are inverted. 1 is on IPv6 so it should have IPv6 src and dest. 2 is on IPv4 so it should have IPv4 src and dest.
Posted by René Giller at 19:12
typos in cc.pdf
Hi, I think I found some typos in cc.pdf :

p.6, first paragraph :
...Source i enters node i, uses links [(i + 1) mod I] and [(i + 2) mod I], ...

but this is not consistent with Figure 1.2 below, it should be :
...Source i enters node i, uses links [i mod I] and [(i + 1) mod I], ...

the same applies 2 lines below.

p.19 last line :
...then we must have u0 = 0.

but it should be
...then we must have u0 = 1.

otherwise, it won't be an increase anymore.

p.26 third point of the list :
additive increase, multiplicative principle is used

the word decrease is missing after multiplicative
Posted by René Giller at 17:17
Comments (1)
twnd multiplicative decrease
cc.pdf, bottom of the page 28:

1. multiplicative decrease for twnd

twnd = 0.5 * min (current window size)

should be

twnd = 0.5 * current window size = 0.5 min (cwnd, offered window)

which on the figure 2.2 gives decrease of twnd to cwnd/2, or to 2*segments size when cwnd/2 is smaller then 2*segment size.
Posted by Slavisa Sarafijanovic at 8:21
I think that there is an errata when you say on page 18 at the beggining:

11 Mb/s for link X-Y
10 Mb/s for link Y-D1
1 Mb/s for link Y-D1

Y-D1 is twice....
Posted by Javier Sanchez Tamargo at 0:56
Comments (1)
last thursday: 3.4 instead of 3.3
small comment to those who missed the last exercise session: we did exo 3.4 and not 3.3 as previously announced.
Posted by Manuel Flury at 16:30
typo problem cc.pdf
End of page 6 (cc.pdf):

"Then we have obviously λi = λ and λ'' i = λ'' for some values of λ' and λ' which we compute now."

Please indicate the correction.
Posted by Raphaël Tagliani at 15:53
Comments (1)

I think there might be a typo in the tutorial on cc.

On page 21, section 1.6.1

Shouldn't the equation 1.21 be without the 1-nixi? but as the one above and the next one (1.23)

mui * (nixi + ri) ?


Christophe Gudin.
Posted by Christophe Gudin at 19:49
Comments (1)