Distance Vector Algorithm (Bellman Ford) - Computerphile

Underpinning the Internet are countless network routers - how do they work out the route to send your data along? Dr Richard G Clegg, Queen Mary University of London explains the Bellman Ford distance vector algorithm.


This video was filmed and edited by Sean Riley.

[BonJoviBeatlesLedZep]

We had a Computer Networks exam involving distance vector algorithms yesterday and NOW this video gets posted. Just my luck.

[talideon]

I had fun times with this stuff a two decades ago. In my college work placement, I had to get a bunch of MEMS talking to each other in a mostly reliable fashion, which meant figuring out mesh networking and what to do when you have very unreliable routes. That was a harder problem than my mentors (who were electronic engineers, not software engineers) realised... It was certainly a learning experience!

[davidgillies]

Bellman-Ford not having been invented by Bellman and Ford is an example of Stigler's Law: no scientific or engineering discovery is named after its originator. Stigler himself credited Robert Merton as the original discoverer of the law in a nice bit of self-reference.

[TechyBen]

Overhead projectors in 1990: Blurred focus on the wall.
Overhead projectors in 2020: Blurred low pixel count Youtube.

[zwz.zdenek]

It's one of those things you need expensive equipment for and so much planning needs to go into making it work that only those at the top do it. A regional network, especially with damage and/or overloaded paths has to be managed by hand.

[Enigmatt_eu]

University bells ringing 🔔 Thanks for refreshing my knowledge @Computerphile 🙏

[ndle_king]

3 years on I think I've forgotten the details of every algorithm from my networking class :(

[donaldkjenstad]

Back in the '70's we were writing algorithms for minimal spanning trees ....

[felineboy]

then Black becomes overwhelmed and the whole networks becomes slower, and that reminds me of Braess' paradox.

[victorcotu]

I'm glad to see that I'm not the only one to have stolen continuous form paper from the lab.

[JoshTheCoder]

I would give away my car to have an hour in the classroom with this guy

[sasukesarutobi]

Can the algorithm account for directness? It seems from Dr Clegg's explanation that the count-to-infinity problem arises from nodes exchanging second-hand routing information back and forth, so weighting information by originality would help updates propagate quicker. (Unless that's one of the hacks he alludes to.)

[wylie]

Great video. Cleared things up for me, very well explained.

[JmanNo]

Immediately i must say fantastic idea of webcam

[theinnerwaffle]

I'd watch a video on the Counter Infinity Problem.

[daddlplays]

much more complicated explained that it is, hes a professor so that explains a lot.

[AnaS-lpmf]

Thank you so much this made sense of everything!

[joshroberts]

This video does a great job of showing a run of the algorithm, but doesn't explain as well the problems it solves

[LaserFur]

I would think a better way to look at it is to leave the initial blocks and then have sub lists from each router. So it's a one blue followed by one red.

[vinayakf]

Just finished watching Dijkstra algo 😀