5.2-2 Bellman Ford Distance Vector Routing (updated)

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@bobjones1196 Жыл бұрын

When I was a wee lil boye back in tallahasee I really just wanted to learn what the internet was like a city boy. Jimbo my man you are making that come true. As my gran pappy used to say, you're one of them people who've went and gotten dem selves a heart the size o' Texas.

@devinbrown9925 24 күн бұрын

I love this comment. It's so wholesome and a great start to my day!

@nirmalkarthik5892 Жыл бұрын

This was amazing! I feel like my mind has been expanded.

@bumjuncho3246 2 жыл бұрын

Dear professor, shouldn't it be {9, infinity, 2} @10:50, for calculating Db(d)? I am a bit confused by why it's {9, 2, infinity}. Thank you for your time and effort for all of these greate videos!

@emresafacelik5016 2 жыл бұрын

You are right but it is probably a set so it does not have to be ordered, it is bad for explanation though

@ricp Жыл бұрын

yeah, i'm glad I'm not the only one that saw it... it was confusing me. It should really by (9, infinity, 2) like you suggested

@chienthan12345 Жыл бұрын

I noticed the same thing

@svrzaslon 2 ай бұрын

prof's calculation is correct , for calculating Db(D) -> min(Cb->a + Da->(D) , Cb->e + De->(D) , Cb->c + Dc->(D)) -> (9 , 2 , infinity)

@goedeck1 11 ай бұрын

Why does z care about path to x via y when x direct is the min.

@ijyoyo 12 күн бұрын

Interesting would love to know what other uses for this algorithm is. But for now networking is great!

@evelynellis8003 Ай бұрын

I know you haven't made a video in a long time, but if you spare a second, could you explain poisoned reverse? I cannot find you talking about it, and the way you explain things help me immensely in my networking class. Either way, thank you for doing such excellent work!

@yoki004 Жыл бұрын

I think there might be an error at the slide on 17:50; seems like 50 should be 5 and the 60 should be 6 despite being spoken as 60?

@MiaoMiaoMiMiMi Жыл бұрын

The slides also have small errors - bullet point 3 should be y computes new cost to x via "z" (instead of y)

@goedeck1 11 ай бұрын

Yeah when did x,z go from 5 to 50. The book I have is the same way. Also, do packets get sent before and during all the routing cost settlement?

@cclemon2531 9 ай бұрын

@@goedeck1 we should consider the path from z to y to x which is 1+4. As we not only focus on the direct path.

@torvasdh 7 ай бұрын

idk if this is too late, but each node only knows of it's neighbors. It can't see the full graph. So; Y has it's direct link to X set to 60. Y sees that and asks its neighbors what their link costs are. - Neighbor X says its cost is 60 - Neighbor Z says its cost is 5. That 5 comes from the path of (Z->Y->X). Remember, the neighbors don't say what the path is, just that it's cost is lowest. Y doesn't know that itself is in that shortest path from Z. Y now sees cost of 5 from Z, so it uses that and adds 1 to it for it's own cost. Y->X is now 6 and it alerts its neighbors. Z receives an alert from Y that is has a new lowest cost. That cost is 6. Z checks its neighbors link costs: - Neighbor X says its cost is 50. Z now sees cost of 6 from Y, so it uses that and adds 1 to it for it's own cost. X->Z is now 7 and it alerts its neighbors. Z then alerts Y and X of its new lowest cost and the cycle repeats. This process will rebound back and forth with Z and Y alerting each other back to back until the link cost hits 51, where the new path from node Z->X will choose the direct link to X instead of through Y (which is now 51)

@williamfernandez1241 7 ай бұрын

@@torvasdh That makes sense. So there's no typos, actually?

@MrBusinessinn 2 жыл бұрын

Dear professor, why are the components in Bellman's formula differently assigned? For example the first element in parentheses -> cost is signed with c and the other cost with D? Thank you

@Mimonsi 2 жыл бұрын

Becasue the cost using "c" is the local value (a variable), and the D is a function, because it is received from another desination, maybe a bit like a recursive call.

@goedeck1 11 ай бұрын

9:32 To be in the right order shouldn't Db(d)=min{Cb,a +Da(d), Cb,c + Dc(d), Cb,e + De(d)} = min{9,2,~}=2 ? ~= inf. OOPS LOOKS LIKE SOMEBODY ALREADY NOTED THIS😮

@ren5124 3 ай бұрын

I don't quite get the bad news travels slow issue. Can't you just clear parts of the routing table that'll be affected by the link cost change and do the update from there?

@elvinaguero4651 Ай бұрын

That's the lagging of the packages...