Hop-by-hop routing | Networking tutorial (11 of 13)
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- Опубликовано: 28 окт 2014
- A closer look at the IP header and how IP packets are routed hop by hop.
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This video is part 11 of an intro to networking tutorial: • Networking tutorial
I watched all your tutorials until this one for the moment and I took a lot of relevant notes and printshots.
Everything is clearly and very well explaind.
I can say that I didn't find any tutorial on youtube as accurate and as complete as yours.
Thank you very much Ben for this gift.
this video is 8 years old and yet everything is still accurate, including the fact that ipv6 is still not in widespread use
I learned this in 1991 IIRC so 32 years ago it worked like that. But Internet is older than 32 years. World Wide Web is now 32 years old.
I think between 60 and 70% of internet connections in the United States support IPv6 and even more in a lot of Asian countries do, so its somewhat widespread at this point. It still has a ways to go to supplant IPv4 as the dominant internet protocol to my dismay.
8 years old videos, made by this genius man, have really helped me understand what my teachers at Uni couldn't. I am really glad I found this channel and forever thankful to him for this series of Networking. He made it so easy to understand all of these protocols. Nothing but respect for this man! Excelent teacher!
Ben, you are an awesome tutor. Thank you so much for these amazing videos. You are the only one on Internet who explains these at the fundamental level.
This series of video tutorials are the BEST ones I have ever seen on this topic!!! Thank you so much, Ben.
I feel 95% of other tutors don't *really* understand what they are explaining. Such amazing detailed description of what is actually going on under the hood are rare gems. Thanks Ben.
I just finished this series. I just want to say thank you for putting this up. Your video helped me understand this subject better than many of the courses online.
Just wanted to add to the praise. Those are some of the best tutorials I've seen. Thanks for all the work yuo do.
Thank you so much for these tutorials. This is the first time that I'm understanding so well the Networking. I know that this requires a lot of time and effort but please, keep doing this stuff. You have a really nice gift for teaching.
Great video tutorials. They helped me to explain myself the how the different type of networks and futhermore how the the OSI model layers are connected each other what actually are protocols and frames and packets. Thanks man. I appreciate that.
More comments for more traction. I haven't been professionally trained in anything computer or IT and yet am able to follow exactly what you're explaining here. Thank you so much for creating these videos and keeping them up for all these years. ❤
I know this video is old - but wanted to say you do a great job explaining what's involved, and equally good job show what is inside the Ethernet frame and IP Packet. Thanks!
Thank you so much Ben! You are the most talented teacher. Also I see so much effort you have put in in order to make things easy to understand.
Finishing this up tomorrow, u sir are a legend, love how you explain everything from the ground up, this is really valuable content
Tjhanks a lot Ben, I read lot of articles about how the information has been exchanged. This is the best for clear and simple understanding of the networking concepts.
You are a genius. I wish you made more videos of networking. I am going to memorize each and every word of your tutorials.
you are the best. i give you 99/100 for the past 3 videos. 1 point down for missing explaining mac address rewrites between each router hops.
one thing you missed and im surprised because you seem like a very accurate person almost to a very high ocd level.
as the packet jumps from router to router while navigating each mini network (the white cables in your pic), the source and destination macs get re-written to help it navigate each little network segment.
sidenote: as the packet hops from router to router the mac addresses get updated with every router hop. however, the source and destination IP remain the same so we don't forget wher we came from and where we are going. (unless going thru a NAT or PAT which in the illustrated case doesn't exist)
as the packet reaches SFO and then leaves to DEN
the src MAC changes to SFO-mac-of-em2
the dst MAC changes to DEN-mac-of-em1
the src IP remains 192.168.9.2
the dst IP remains 192.168.20.2
Thank you so much ! You are the best teacher on RUclips. Your videos are easy to understand !
Super helpful Ben. I wish there were more such videos to explain everything. Thank you.
As everyone else has already said, these tutorials are amazing. You managed to explain these networking concepts very very well.
Oh thank you SO MUCH Ben. Your videos REALLY helped me.
Absolutely awsome videos Ben.the best videos on you tube.
Thanku so much .these have helped me loads,to learn about the internet setup and network.setups too.as a hobby.
To compliment my passion as a qualified electrician,in the UK
Thank you Ben Eater, you're the best!
Props for having the routing table output from a Juniper device!
A lot of people would have used Cisco.
I love you man! Awesome tutorial!!!
This is awesome material, thanks a lot
GREAT series!
Thank you very much for this magnificent content!
6:40
start of hop by hop (next hop) routing.
Much better than my university teacher!
Great video and explanation
Such more learned today, thank you
Clear and concise explanation.
Excellent tutorial.
Excellent vidio Sir.God bless u
You're aweasome thanks for making useful videos.
Very well explained.
great talk. crystal clear
Thanks a lot for this awesome tutorial. Really helped me in understanding the concepts. Can you also please provide tutorials for Wireless LAN and Bluetooth?
Well explained, better than entire my CCNA lol.
Hi Ben, thank you so much for this incredibly clear series. Amazing job. One question - what software are you using for illustrating the presentation?
Absolutely brilliant videos Ben. PLEASE can you do one on the OSPF routing protocol?
Ben you are amazing could we have more of these
Incredible 🥰
Good stuff. Thank you
Ben ,thank you...
this dude is best
sooooo helpful
very nice information and please make video on TCP congestion control
How did you get the information of the different nodes, or ISP like SFO and DEN?
Thanks!
THANK YOU SIR
beautiful
What happens when the sender's IP (or whatever subpart its IP belongs to) is not listed in router's table?
I assume that sending packets between DEN and NYC also requires an ARP, right? The routing table contains just the IP of the next hop, without a MAC address.
How do the interfaces know whether to send a PPP frame with the message or an ARP request followed by an Ethernet frame with the message?
I'd really love to see a video on routing algorithms
Thanks a lot
Knowing this architecture, is it possible to put this route on SFO : 192.168.20.0/24 port2 next-hop(NYC IP address)??? Thank you
the TTL field is so clever. I just know if I had designed the IP protocol I would not have thought of that LMAO
Hi, I didn't know where to go for this so I'm going to comment sections regarding ISP routing. I had Xfinity in New Jersey. To a server in Quebec, Canada, I had gotten 40 ping. However I moved 20 minutes from there in a suburb extremely close nearby. Now, to the same server in Canada, I now have about 15 ping. I am so curious, but cannot figure out what could have been the problem there in terms of routing efficiency there. I've done traceroutes and the like, I don't know enough about the gateways to actually diagnose where the problem was. Was it a problem on my ISP's side? (also, on another server to Ashburn Virginia, at my old apartment I had gotten 60 ping with the same provider, now at my new house, I get about 8-10)
hey ben! any chance you can make a video about the QUIC protocol?
What populates these routing tables? I'm assuming at some point they are empty.
That's a great question. If a network company needed to implement a new router into the topology, how would the rest of the routers on the network know that there was now a new router. Well, to put it simply, a routing protocol constructs the table. The protocol that is used is really dependent on the type of environment the router is subjected to, but two common routing protocols are OSPF (link state routing) - which uses Dijkstra's algorithm to calculate a link-state database (which opens the shortest path first, OSPF = open shortest path first) , and RipV2 (distance vector routing). RIP uses the bellman-ford equation to calculate the 'least cost' between each node.
This is just introducing you to 'what' exactly constructs the routing table. If you want to know 'how' it happens, then I would suggest reading this - en.wikipedia.org/wiki/Routing_protocol
Those are protocols for exchanging routes. But in the end, you have to place the routes somewhere manually so they can be exchanged. Most of the routers won't have any directly connected networks, but those which have (Like SFO and NYC in the video) have to advertise it to the others, and they are set manually.
Thanks, Ben. I learned a lot from your network tutorial, and have a question. 192.168.x.x is known as a private network range - what happens, if my local network has a machine with 192.168.20.2?
So this where NAT comes into picture. Whenever host on local network sends a request to public host (google.com); router does a port mapping (192.168.20.2:80 -> 72.124.123.113:78200). This translation happens for both TCP & UDP connection. Translation entry would be kept with router memory till connection closes. Now google.com is going to respond to your router's public IP address on port 78200. And router will fwd it to local host on port 80. Ping also some kind of a translation but it is not based on port. It uses a ping seq.
for year 2014 this is good explanation, I hope to see one long video with animation to "the trip of hello word! page over internet" or I will made it myself from zero
Is there a protocol that remembers the hops so that it doesn't have to look through all the routing tables for each hop?
Such a protocol would have to be implemented somewhere and that would be in the router. The routing table is a (distributed) mechanism for remembering the route, but it is better than that because the route can change over time. The routers update their tables automatically as routes become available or unavailable. In practice, the lookup isn't so bad because hot spots will get cached and the table gets stored in a way that is efficient for looking things up.
An alternative may be that each packet would have to carry the entire route that the routers would then execute when forwarding. This is problematic because two packets sent one after the other to the same destination may take different routes due to various network conditions, so there is no way for a sender to know what route a packet will take. It would also be expensive to have to determine what the route should be before sending every packet. The forwarding mechanism described above is efficient because every router only needs to worry about how to get the packet closer the the destination, not all the way to the destination.
Thanks
how are routing tables built?
At SFO, we are changing the ethernet header by changing the source hardware address with mac address of SFO and destination hardware address with mac address of DEN. is it true ?
The SFO-DEN link uses PPP, not ethernet, so it doesn't have a mac address.
Hi, great tutorial, thank you for that! I learnt a lot, but i still don't know why i can't ping my friend. I know his IP and we are both connected to internet. Do you know, what can cause this ?
Late reply but why not.
The problem is caused by function called NAT.
NAT hides your local IP from public internet and no one can access it.
If you want more information you should check RFC 1918 documentation.
@@guckesksk5895 now i know it, but thanks anyway :D
Ben , can i get Hop-by-hop routing | Networking tutorial (12 ) url//.... ??
On the routing table it says
192.168.20.0 /24. •[OSPF/10] 00:09:24 metric 3
What does the [OSPF/10] 00:09:23 mean and in particular the /10 and 00:09:23
He does mention in an earlier video that /10 means that the first 10 bits of the adress should be read as a prefix, so when an IP adress comes in only the first 10 bits are read before routing it further, as the router knows which of its port leads to all adresses that begins with these 10 bits.
What sort of black hole have I got myself into..
@BenEater ... auto-generated subtitles option ON please :/ {I guess the video owner has to enable it}
See en.wikipedia.org/wiki/IP_address, under Private Addesses. 10.x.y.z and 192.168.x.y are private addresses: "These addresses are not routed on the Internet and thus their use need not be coordinated with an IP address registry.". On the other hand, changing 10.x.y.z with 11.x.y.z and 192.168.x.y by 12.w.x.y would behave, in real world, as explained.
Note also that when the terminal number is 0, that designates the whole (sub)-network. 192.168.10.0 (It is a class C address, so the terminal is the last octet, which is thus 0 ) means the said network (or sub-network), not a specific terminal or router. If the terminal number is filled with 1_b, such as 192.168.10.255 , that means that UDP like is used (broadcast to all terminal in the network, here, on 192.168.10.0)
thanks, exactly what i needed!
Weird how San Francisco doesn't suggest going by ATL or NYC to get to 10.0.8.0/30 when they're both 3 hops to get there. I'm assuming this was made by Ben, so a human error, or it might be something else.
San Francisco is not directly connect to either of those locations. All traffic to 10.0.8.0/30 has to go via the Denver router.
What is DNS?
Domain Name System. It helps resolve a URL into its IP address and vice versa.
Dear Sir, I have watched almost every of your videos. I kindly request you to build a series on internet connection on the custom hardware like the 8 bit computer or the 6502 computer. I am currently building a 32 bit computer with vga output and a usb keyboard, mouse input. I am also planing to build an OS for it. From your kind subscriber. Thank you for your kind support.
So wait a minute. So if I use my custom router at home to connect to the ISP router, I would be able to respond all the ARP requests there. In theory I could spoof all my neighbors' requests. Holy shit, SSL is important.