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How does your home broadband connect to the Internet? (PPPoE)

How does your home broadband connect to the Internet? (PPPoE)

Hello, everyone, here I am again. “How does your broadband connect to the Internet?” Sort of a series, both for fellow network engineers, together to exchange and cut; also for readers interested in the network friends, together to explore fresh. Tonight I’ll simplify and abstract the PPPoE involved in the home broadband service, and share it with you! Previous Review
The sky was always blue then, and the days always passed too slowly; and today? The days whoosh past. Looking at the previous article records, the last article in this series, was released a year ago. How is your home broadband connected to the Internet? (GPON access network) A little summary: access to the physical line from the telephone line to the development of GPON. GPON in addition to high capacity, high multiplexing, I think it is a good solution to the problem of power extraction outside the server room curbside buildings and other places, greatly reducing the cost of communication and coordination and the hidden danger of electricity. Take the fiber to the home (FTTH), the whole time it only needs to take power in the server room (OLT equipment), all the way to no power (passive splitting network), until the user’s home optical cat (ONU) need electricity. Peers who have done access should be better understood, in the scope of his property, taking electricity is sometimes more difficult than the sky. After a brief review of the previous article, we now have the line pulled into the home. This is the so-called “wired broadband”.

PPPoE
After the physical line is completed, we can use different technologies and arrange different services according to the needs of different scenarios. Usually, most people will open a home broadband service. Home broadband is now commonly used is PPPoE technology. PPP is a link layer technology, I have done an introduction in the earlier article [Practical] Interconnection IPv4 address mask 31-bit end egg section, and did a packet capture demonstration. Ethernet is another link-layer technology, and most of what we call digital communication networks today are in this category. The communication between different devices in your home LAN is basically based on Ethernet technology. Its characteristic is that it can realize multiple devices networking at low cost, but the control ability is limited. One has good control ability, but only point-to-point; one has poor control ability, but can point-to-multipoint. So, smart people cleverly combined them and PPPoE, that is, PPP over Ethernet, came into being. PPPoE uses Ethernet to form a network with a large number of hosts, connects to the network through a remote access device, and uses the PPP protocol to control each host that is accessed, with the characteristics of wide application, high security, and convenient billing. Experiment preparation We start from the product documentation and look for the PPPoE configuration experiment. In the real network, there are many devices that support such experiments, but considering that sharing out must still have reproducible meaning, I still cut from ENSP.

Careful you should not be difficult to find, through this kind of manual, we can carry out network knowledge learning. [Practical] About product documentation reading

Careful you should not be difficult to find, through this kind of manual, we can carry out network knowledge learning. 【Practical】About product documentation reading

Experimental topology Now I will do a finishing abstraction of the real network and simplify it into a topology as follows, and allocate some resources. The real network is definitely much more complex than this, redundancy will be considered, protection will be considered, load sharing will be considered, authentication system will be considered as a separate set, etc. This is a miniature version to aid our understanding.

AR1 simulates your home, AR3 simulates your neighbor’s home; AR2 simulates the carrier access router; LSW1 simulates the GPON network. When you go to the business office to open an account, the salesman will give you an account number and password, you take the account number and password back home, waiting for the installation and maintenance master to pull the line can be dial-up Internet. (This involves the business opening process drive, is also more complex, and now not necessarily account password directly to you on the spot, but wait for the installation and maintenance master to get well before handing over to you. (Here is not the focus of this article, from the brief!)

Back to our topology, we’ll follow the manual for these experiments, and we’ll ignore the ones marked optional for now.

Experimental Configuration
AR1 Configuration

Each of the corresponding configuration commands above is clearly explained in the product manual, so if you are in doubt, be diligent in checking them out. Broadly speaking, PPPoE dialing from client AR1 to server AR2 simulates a scenario where you are dialing for Internet access at home.

Each of the corresponding configuration instructions above is clearly explained in the product manual, so if you have doubts, you should consult it diligently. Broadly speaking, PPPoE dialing is performed from AR1 on the client side to AR2 on the server side to simulate the scenario that you are dialing up the Internet at home.

Experimental phenomenon
When you have configured all the above topologies, you may not necessarily see the results immediately, and you may encounter various problems. Problems encountered, check the processing to solve the problem, is the basic skills of network engineers. Here is a term called “troubleshooting”, if you encounter problems, please try to troubleshoot! The manual provides some instructions for checking the results, both server-side and client-side.

On the server side, we can also try the following command.

Check the overall user profile

Various configurations and commands we may not be very familiar with, it’s okay, you can use the form of knocking question marks to get help tips information.

Packet Capture Analysis When you encounter problems with your experiments, or you want to learn the details of the PPPoE protocol, you can capture the packets yourself and find out what’s going on.

Turn off the client’s port and open it again, this process grabs the packet, we can see the whole interaction process.

There is also a process for PAP and IPCP below, so I won’t take screenshots. You can try it yourself if you are interested. You can also take the account password directly with your computer in the real network to capture the process to record the packet.

Summary of this article
Your home Internet service, your neighbor’s Internet service, aggregated together to the large network, this process is called “service convergence”. When we press the light cat or home router (dial-up may have routing mode and bridging mode, the dial-up action may be in the light cat or home router), the PPPoE dial-up device does a lot of interaction with the big network of the operator, and you can surf the Internet only after it passes normally. As ordinary users, we may not even notice; as network operations and maintenance, or curious people, we can snoop through WireShark packet capture and other ways. When we really quiet, read the product documentation, do experiments, and organize the abstraction process, we will find that many of the original ambiguous knowledge points, gradually clear up. This process will be repeated, that is, get once will soon forget, have to get a few more times, repeatedly get repeatedly have new insights. I often hear people complaining about the use of ENSP, here I say it in passing. I could have found some real devices or server simulators to build and demonstrate this PPPoE experiment, but I still chose to share on ENSP to sort it out. Why? Because many of those who want to learn, especially students, do not have a real environment, and many cannot afford to buy a better performance server to run those X86 platform network simulators. In this case, ENSP, GNS3, HCL and other single machine can install a single machine can demonstrate the network simulator or have some use. Of course, ENSP is currently stopped, many of the more advanced experiments can not do, but do some of the basics of learning to consolidate, still more than enough! The beauty of network technology is that those so-called advanced technology, in fact, back and forth is the basic content of the re-encapsulation and iteration. Back to the basics, the foundation is not firm, the earth shakes! Of course, we also look forward to the early arrival of ENSP-NG. Network simulator is only an auxiliary tool, just a means not an end. Which you feel comfortable with which to use, the key is through the experimental arrangement, the effect of reproduction, in-depth exploration, mastering knowledge and methods of dealing with problems

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