How Does Internet Work

I can say at the beginning that more and more fellows are visiting this blog. Finally networking knowledge project did succeed to get some fans from out there so I felt the need to thank you all for visiting this place. As you can see here from the blog post list I didn’t follow this movement myself these days. I actually didn’t come here for some time now. My last few weeks were very intense. One of the reasons was my learning sessions that took me at least few hour a day and the most interesting reason was my new assignment at work. I got an assignment to carry out and even more interesting to secure IPv6 in our company for a whole network segment. At least one segment for now, but it was a nice thing to get me into IPv6 deep dive learning. And I make the last step of the learning like this:

What is better than document the networking job that you did until is fresh in your head. So I write it down for the future implementations but rather than put it into my notepad I do it here on my blog, so next time is easier to search for it and something even better than that, you can use it too.

RA – router advertisement message format from RFC 4861

This time I will write about some of the most important things in IPv6 networking that you needed to know before you go on and carry out IPv6 implementation. RA router advertisements and some strange special bits in the RA packet header that are configuration option flags. Good thing is that there are only a few of them, four to be precise. The bad thing is that at first, I needed a couple of days to stop mixing them up.

UPDATE on 2.11.2013 – There will be an update in February 2014!

Read all about the new announcement in the latest article here! with all new topics added and removed from CCIE lab exam v5.

UPDATE on 23.07.2013 – There will be not update this year to v5 at least not for now…

So, there are some news. The news is that at this moment, few weeks after Cisco Live in Orlando we can say that CCIE lab exam v5 update is not going to happen this year. I other words, for us studying for the lab exam, the old topology and all the topics from v4 are still valid. Many of us will think now that we can be in peace for another year now and try to learn and understand everything so that we can pass the exam before the change. From my perspective, maybe this is not the whole truth. I think that even the change in the exam and all the topics mentioned down here that would change will not necessary mean that the exam would become more difficult. My perspective is that if you are prepared to pass the CCIE lab on v4, you will be probably also prepared to pass it on v5. My point is in that there is so many networking topics covered here that all the changes would not disturb you in your goal, maybe only those people who studied but not really with 100% understanding. The road to CCIE is not short, and is not easy either but it can be fun and in the end it will be worth the effort.

Learn and enjoy the process to, not only thinking on the resulting cert. In that way, you will probably be more succesful even in the CCIE lab changes a bit.

DCCP transport layer protocol is used to control the datagram congestion. It provides an excellent procedure to stop the internet fall down, if it is caused by the congestion. In fact, this protocol is a brilliant competitor to be used as a substitute of UDP protocol.

DCCP account DCCP congestion control trait by means of a reliable acknowledgments delivery (in form of packets instead of bytes) will provide actually a congestion control with dynamism. DCCP will also make available the negotiable blocking control mechanism, but it will be up to the particular application’s specific requirements too. Moreover, these mechanisms come with a number of specific features, so to go well with different types of applications. The bandwidth consumption can be enhanced as the size of packets in case of DCCP is increased.

This story will be a turning point for my blog future starting with a change in writing methods and changing those methods to a more causal fashion.

INTRO

For now all my text here where somehow depersonalized and tech oriented in a way that it was all written like in some book. User manual to me concise. Maybe this is the main reason that now when I got back to revise some parts of the texts there was an impression that those text are very boring. There is something missing inside them, maybe me?
Of course, I didn’t start to write this blog two years ago because there was a huge need for someone new to write about old networking stories about protocols and networking standards. I did start to write because I was young enthusiastic freshy networker who was in his all day job searching, part-time Cisco teaching and CCNP studying period.
That was actually not job free time for me, but it was intense and fulfilling time. Having some experience with web before and now spending whole days with my head inside Cisco Press books it was somehow natural to start a blog. Yes I know, everybody wants to write something on the web, but that is the main reason for this post, I you wondered what is this all about. I can now finally say that if I did not give up writing this blog until now then it’s the real proof that there is actually somebody reading it and that I can finally consider myself a networking blogger but more that all an networking geek. Jup, that’s right, there are people who are not ashamed of being geeky technicians.

Static floating route is static route like any other but with added administrative distance in the configuration

R1(config)#ip route 172.16.10.0 255.255.255.0 10.10.10.2 200

Static Floating Routes are very interesting so I decided to give you a short description and an example.

A static floating route is the same as normal static route except that this kind of static route has administrative distance configured to some value higher than 1.

Remember that if we configure normal static route like this:

R1(config)#ip route 172.16.10.0 255.255.255.0 10.10.10.2

It will send all packets destined for 172.16.10.0/24 network to the neighbour with interface address 10.10.10.2

Of course, this static route will have administrative distance (AD) of 1 by default.

If we make the configuration like this:

R1(config)#ip route 172.16.10.0 255.255.255.0 Serial 0/0

In this case, the AD will be zero (0). Pretty cool right? There’s another article about that here.

In either case, this is normal because this is the way we configure routing on our router or if we use a dynamic routing protocol, this is then the way of overriding routing protocol decisions for some exceptions.

But what if we want to use a static route to make something completely opposite?

If we want to use static route only to be a backup route. Then we will need to give the precedence to the path learned by some IGP (Interior Gateway Protocol) like OSPF for example. We know that most paths (routes) learned by OSPF protocol have Administrative Distance of 110. In that case, the Administrative distance of a static route needs to be bigger than 110 if we don’t want to kick out the OSPF route from routing table.

If you know what delay is, jitter is simply the difference in packet delay. In other words, jitter is measuring the time difference in packet inter-arrival time.

It is a specific phenomenon that normally exists in bigger packet-switched networks. As a time-shift phenomenon, it usually does not cause any communication problems. Actually, TCP/IP is responsible for dealing with the jitter impact on communication.

On the other hand, when we speak about Voice traffic and VoIP network environment this can be an issue. When someone is sending VoIP communication at a normal interval, (let’s say one frame every 10 ms), those packets could have stuck somewhere in-between the network and not arrive at expected regular pace to the destined station. It is not usual, but the packets could take different routes or get load-balanced through two similar paths where one of those is congested in that moment.

That’s the whole jitter phenomenon. We can look at it as the anomaly in tempo, with which packet is expected to come and the time he was late to really get there.

In the image above, you can notice that the time it takes for packets to be sent is not the same as the time in which they will arrive at the receiver side. One of the packets encounters some delay on its way and it is received a little later than it was expected. Jitter buffers are entering the story. They will try to remedy packet delay if required and if possible. VoIP packets in networks have very changeable packet inter-arrival intervals because they are usually smaller than normal data packets, and are therefore more numerous, with a bigger chance to get some delay.

If you have one network card (NIC) inside your computer, everything is working fine and your computer can speak IPv6 to all others in the local network.

On the other side!

If you are one of those guys (strange networking guys who run strange labs on their big PCs), having more NICs inserted in their machine? In that case, your PC will have two or more network interfaces and every one of them will have the same network identifier fe80:0000:0000:0000. If you go back to networking fundamentals, you will remember that a host (or router) with more interfaces cannot have two of them with IP addressing from the same subnet.

Why?

If you want to ping the address fe80::5c9f:bc10:bb38:63ec from your computer and your computer has two NICs with addresses fe80::1111:1111:a000:0001 and fe80::5555:5555:5555:1111. Out of what interface will the ping exit the computer? Hm, on both? Only on random one? This is not going to work.