Category: Networking

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.

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.

In short RADIUS means Remote Authentication Dial-In User Service server or proxy.  Is used for centralised accounting, authorisation and most of all, authentication. This technology will help you control who will be able to connect to your network and who will not be granted the access.

It can control the access for all sorts of networks, wireless, VPN, dial-up, direct device to device like router to router connections, basically wherever you put it the middle of communication he can do the control.

There is also RADIUS proxy configuration where proxy only receives and accepts the connection requests but for the decision making it will be connected to other server who will do the RADIUS role.

There are two major ways to deploy radius server and that are:

• Deployment of FreeRADIUS server on UNIX servers. This is by many network engineers basically a best daemon which implements radius protocol and makes your UNIX server a RADIUS enabled server.
• Deployment of IAS role – Internet Authentication Service on Windows Server machine will allow you to make your Windows Server machine respond to RADIUS requests and act as a real RADIUS server. It includes some AD stuff implemented in so it will be able to authenticate the users from Active Directory domain. Which is his biggest advantage over UNIX deployment of course if you have AD deployed in you organization, and you have surely.

RADIUS server connects to user account database which is Active Directory in Windows Server or some normal user database in UNIX. Can be normal SQL table with users in it and can checks access credentials. If the user is authorized to access some network that is secured with RADIUS, he will authorize the access for that user and writes a log of the user entrance to the network.

Components of a RADIUS infrastructure