DPQ2160; User manual; Cisco DPQ2160 User Manual. Docsis 2.0 cable modem. Modem Cisco Cisco Model DPC3000 and EPC3000 DPC3000 User Manual. Docsis 3.0 cable modem (36 pages). Wizard window, and then click Next. Click Next in the Found New Hardware Wizard window. The system searches for the driver file for your hardware device. The DPQ2160 by Cisco was hard to come by - but we have it! We just narrowly escaped an attempt by the Mangalores to commandeer our ship and steal our cargo.
Cisco Dpq2160 - Ethernet Doesn't Have Valid Ip Configuration Dec 7, 2012 this error is popping up when i'm trying to connect my pc to modem(cisco dpq2160) through cable.' Ethernet doesn't have valid ip configuration'. I have also tried some solutions given in other sites like ipconfig/reset in cmd. It says that there are no settings to reset.
Similar Messages:. ADVERTISEMENT Mar 16, 2013 the same thing happened to me Thursday as well.
All the laptops and my friends computer(same exact build as my own.) had been able to connect to the internet via wireless/ethernet. However my computer does not. For quite a while it would say the address doesn't have a valid IP, now it thinks there is nothing wrong. I had wiped and reinstalled windows 4 times in a sorry attempt to fix the issue. Also, I had checked the driver for my internet and reinstalled the latest version several times. I've exhausted all the resourses I can think of Mar 16, 2013 I'm using an ethernet cord to connect to my internet and it has been working well until Thursday morning when I turned on my laptop (Windows 8) to see a yellow triangle sign in the bottom right hand corner, in front of the ethernet connected symbol. Since then I haven't been able been able to access the internet from my computer.
When I hover over it, it says that it is an 'Unidentified network' and there is 'No internet access'. I've run the Windows 8 troubleshooting and it says that the problem found was 'Ethernet' doesn't have a valid IP configuration', but I'm unsure how to fix it. I'm thinking that the problem is to do with my computer rather than my network, because I've tried another laptop (Windows 7) through the same ethernet cable and connection and the internet works fine on the other laptop. I've tried so many fixes that I've found online, with none of them actually working.
Yesterday I even tried a full system reset, where I reinstalled Windows 8, repartitioned and wiped everything off the hard drive, but it still appears have the exact same problem. Today I also purchased and tried a new ethernet cable which didn't work, so I then purchased a USB to Ethernet adapter, to make sure that it wasn't my ethernet port on my laptop that was faulty. That didn't work either, and the same problem still remains. Apr 4, 2013 I have the same problem in running win7 64 powerline adapters all 3 light green stable and getting 'doesnt have a vaild IP config' error msg Windows IP Configuration Host Name.:.-PC Primary Dns Suffix.: Node Type.: Hybrid IP Routing Enabled.: No WINS Proxy Enabled.: No code. Apr 3, 2013 I have an ethernet connection using a Powerline (TL-PA2010KIT), which I use for online gaming. It's been working perfectly, until today.
For some reason, I can't connect - I get the little 'Limited access' symbol,and no mentions of an actual connection.However, I have a wi-fi connection that works perfectly, besides fluctuations in connection sometimes, which makes it unacceptable for online gaming. I'm using a Virgin Media Superhub, so I assume that there's no problems there if the wi-fi works. Also, I'm using Windows 8 if that's any concern. As for ipconfig: Windows IP Configuration Host Name.: adam-pc Primary Dns Suffix.: Node Type.: Hybrid IP Routing Enabled.: No WINS Proxy Enabled.: No code. Sep 20, 2011 Whenever I try to connect Windows XP with Windows 7 I get an error 'Local Area Connection' doesn't have a valid IP configuration.I have tried a lot of tutorials and answers on different forums but could not get the answer. Mar 3, 2013 I recently bought a desktop off craigslist, it has been working fine for the past month, but I was about to start up a program and it froze.
(was beginning to overheat, so it froze.) So no problem, I reset the computer and when I logged on, the internet had a fashionable yellow! So I diagnosed it and received the 'Local Area Network does not have a valid IP configuration.' Now every single computer, wired or not, can access the internet so it is specifically my desktop. I have done literally everything suggested in multiple forums, and nothing I do seems to work. I figure instead of listing everything I have done, I will just assume that I either did it wrong, or was given false information on how to do it, so in case one of those hold true I won't be stuck thinking something didn't work.Internet was working -Computer froze -Reset Computer -Internet no longer working on my computer (does on other computers) -Local Area Network does not have a valid IP configuration Apr 21, 2013 I'm having trouble getting my laptop to connect to the Internet over wi-Fi. If I plug it directly into the router with a cable it works fine.
I have 10 other things in my house that connect over wi-Fi just fine, my pc just won't connect. Oct 9, 2012 I know this question seems to come out a lot but I can't seem to fix it.
I am a college student and my internet has worked 100% fine until I went home this weekend and came back. It worked this weekend when I brought my computer home and when I came back today it gives me this error when I try to troubleshoot.
The only thing that could have changed is when I went home I set my DNS to be openDNS because it makes a huge difference there, but I changed it back when I got here. I don't know if that would matter, but unplugging and restarting are doing nothing. Feb 25, 2013 I am having this problem on my acer intel core i3 laptop I think my Network adapter is corrupt I cannot connect to my Netgear(home) router anymore. I use to be able to troubleshoot/diagnose and fix the error but now it doesn't fix it anymore.Wireless works though.the problem only occurs when I plug a network cable into the NIC. I have tried other network cables and the router at work but it gives me the same error.things I have tried to fix NIC that did not work cmd- iprelease/renew changing things in the registry changing mac address updating netgear firmware updating NIC driver uninstalling the bonjour service I have tried putting the ip address.dns in manually?i am running on windows 7? Sep 21, 2011 I have been having a lot of trouble getting my computer to connect to the internetIt is only one computer on the network that consistently has problems. It was working ok recently, except that I would have to turn the router off and back on fairly often, because the computer would say that the DNS lookup failed.
Today it stopped working, and now says that the adapter does not have a valid ip configuration. I do not know what to do. Aug 22, 2012 Randomly today my internet cut out I tried resetting the modem/powering it down etc nothing worked.
I then tried the windows network diagnosis and it resulted in this issue 'local area connection 2' doesn't have a valid ip configuration. I'm also directly connected to my modem if it matters. I never had this issue today. This issue keeps randomly occuring. I have a modem/router combo Cisco DPC3825 DOCSIS 3.0 Gateway Jun 6, 2012 I have been facing the same problem with my wireless connection.
I can connect to all the wireless connection except one, and it shows yellow exclamation mark in its icon. Feb 8, 2013 Windows 7 Connects to local network ok, but No Internet Access, i tried to reset dns, tcp/ip, but the same problem appear, but when I'm trying using modem, internet is working fine.i get the yellow triangle with exclamation point in the taskbar saying 'No Internet Access'. I've tried shutting off the firewall, setting the connection to public, etc. With no change. I've also gone through the Windows Network Diagnostic process and it says. 'local Area Connection 2 doesn't have a valid IP Configuration' Sep 20, 2011 Whenever I try to connect Windows XP with Windows 7 I get an error 'Local Area Connection' doesn't have a valid IP configuration. Jan 3, 2013 I have a laptop that use to connect to the internet fine, now it connects to the network, but won't connect to the internet Oct 27, 2011 It's only occurred recently.
May 5, 2013 error: 'local area network doesn't have a valid ip configuration' Problem on another machine: aCER aSPIRE w/ windows 7 Had internet previously; no changes made to machine EXCEPT swapped hardware internet connection from Links router to a temp set up on a laptop.Couldn't get laptop to connect via hardware - went wireless instead Upon return of cable to ASPIRE, got above error message. Running connection Wizard doesn't do it! Aug 1, 2012 So I built a PC recently, using Powerline for Internet access.
At first the PC wouldn't connect to the Internet so I moved the wireless router and the Powerline plug into another room and plugged them directly into the wall socket (previously they were plugged into an extension lead). I got Internet access on my PC, but 2 laptops and another PC were having trouble connecting to the Internet using Wi-FiWhen I moved the router and Powerline plug back to their original place, my PC wouldn't connect again (all other computers could) and I got the 'Local Area Connection doesn't have a valid IP configuration' error from the network troubleshooting tool.So it's either I'm the only one that does get Internet when I move the router, or I'm the only one that doesn't get Internet when the router's in its normal place.CODE Mar 8, 2011 The above problem has just occurred. I am networking a W7 computer to an Windows XP SP3 via a Cat 5 cable connection.
Checks of all cables and NIC interfaces show that there ok. I can ping each NIC card and get a response.
The NIC cards are configured for obtaining automatic addresses. My connection to the Internet via a Motorola Surfboard modem is ok. I have checked the drivers and they are ok.
Apr 5, 2012 After my last usb wireless adaptor went faulty after a few years of use I needed a new one for my home PC.Since I had never had problems with my previous Belkin adaptor I opted for another one. Model number F6D4050 V2.I am having no luck at all connecting to my home network with my PC, the laptops and games consoles at home have no trouble at all. Windows troubleshooter brings up the fault: 'wireless network connection 2' doesn't have a valid IP configuration.
Jan 9, 2012 I have a WRT54GC Router with 4 Windows 7 (all Home Verions)PCs.3 were running hard wire LAN, one notebook I was using wireless.I logged into the modem to change my security settings.I no sooner tried to save a password change, when the router locked up.I lost all internet connections. Did the normal reset modem, reset router, reboot, etc thing.Bottom line, I took out the router, and have just an 4 port switch connected to the modem.One desktop PC off of the switch still connects.
On all other 3 PCS, I get the dreaded 'Local Area Connection Doesn't Have a Valid IP Configuration.' It's not a switch or cable problem. I connected my notebook via LAN to the same cable as the one PC that still connects, no luck.I've tried the ipconfig/release and renew, no luck. On the notebook, I even did a restore to a point about 3 weeks ago, no luck. Then today reinstalled the O/S. Mar 10, 2013 I live in student accommodation and the other day my wired connection to the port in my room suddenly stopped working and the error message in the thread title appeared in troubleshooting.
Aug 24, 2011 I just got my internet hooked up in my new apartment yesterday, and it is not working when plugged directly into my laptop. It worked fine on the installer's laptop.A buddy of mine let me borrow his wireless rory to connect. I've tried disabling IPv6, restarting both the modem and my laptop, and updating the ethernet driver, which I could not find (HP dv2715nr is my model and I have windows 7 ultimate). Elow is my ipconfig with the modem plugged in and the wireless turned off. Microsoft Windows Version 6.1.7601 Copyright (c) 2009 Microsoft Corporation. All rights reserved.
C:UsersAllanipconfig/all Windows IP Configuration Host Name.: Allan-PC Primary Dns Suffix.: Node Type.: Hybrid code. Feb 17, 2011 I have a problem with a direct crossover Ethernet connection between two computers. One is a Win XP laptop, the other a Win 7 64 bit desktop. I have a USB adapter on the desktop and the laptop used that to share internet with the desktop. This setup worked fine until today.
There have been no network hardware changes nor software changes but the desktop's power supply recently failed and had to be replaced. After that was done I tried today to plug the adapter and cord back in and use the connection but it will not work. The connection from the modem to the desktop works fine but the connection from desktop to laptop will not detect internet access, says 'Local area connection doesn't have a valid IP configuration' and has limited connectivity. Other than a new power supply absolutely nothing has been changed. Oct 3, 2012 Have a Windows 7 desktop connected to a Netgear Router via a cable modem.
Computer network is setup a Home Network / Access Type: Internet. Error Message:'Local Area Connection' doesn't have a valid IP configuration. Problem is fixed but the problem starts again the next time I start the desktop. Receive the error message once again.
Dec 19, 2011 I have a Netgear wnr1000 v3 router. & At about 12:00pm central standard time. It kinda messed up. This is the Problem.
I have seen this 'Local Area Connection' Doesn't have a valid IP configuration. I've browsed and browsed and browsed. Over and over trying every solution. It's gotten me so frustrated.
I don't want to return the router. Nothing works for me. Jul 20, 2012 I was just playing a game, hosting a server with Hamachi, when all of a sudden, I disconnect from the internet. The Windows diagnostic says what I posted in the title. I have tried multiple things to get this working, but nothing seems to work. I have tried ipconfig /release, then going in the settings and tricking the network into giving me a new IP then typing ipconfig /renew.
And that didn't work. I have deleted the Bonjour thing out of my services. May 9, 2012 I just did a fresh install of windows 7 x64 on a 2tb hd. The only drivers I have installed are the chipset, the onboard audio, usb 3.0, onboard HD GFX, marvell raid controller, and the intel management engine.
The only other program installed is intel desktop utility. My onboard NIC is not working. I get an error saying the Local Area Connection doesn't have a valid IP configuration. I've tried setting the IP's and DNS addresses manually. I've tried disabling flow control. I've tried disabling IPV6.
I've tried restarting the computer numerous times. The cable is fine, it was working yesterday. This also happened a couple days ago when I uninstalled my BigFoot 2100NIC, so I just said screw it and reinstalled it and internet worked great after that. I've tried pinging two adresses and it failed to ping 192.168.1.1 (the router address).
I'm considering just installing the BigFoot I have right next to me, but i'm hesitant because the whole point of the clean OS install was to diagnose a stop 124 BSOD. I guess the question is would I rather have internets or GPU (the hardware I was planning on installing next), but its puzzling me why my onboard NIC is not working. Here's my IPconfig/all. I've already reset ipv4,ipv6 and winsock through cmd with admin. Windows IP Configuration Host Name.: Erik-PC Primary Dns Suffix.: Code.
Jan 27, 2013 I couldn't connect wirelessly to my NETGEAR router because of the 'DNS server isn't responding' error.I then eventually made the rather dumb mistake of doing a factory reset, so now the router isn't even in range apparently Therefore I connected to the router with a wired connection and after a 'Investigate router or broadband modem issues' error I eventually came to the error in the title.Currently I'm connected directly via my virgin modem with a wired connection, so this is my means of creating this thread. Below is what i got from ipconfig /all using a wired connection to my router. Microsoft Windows Version 6.1.7601 Copyright (c) 2009 Microsoft Corporation. All rights reserved.
C:Userschenupanipconfig /all Windows IP Configuration Host Name.: CGPC Primary Dns Suffix.: code. Jul 30, 2012 I am using hp pressario C7000 with window 7 32 bits. Can not access the internet.
The reports 'local area network doesn't have a valid ip configuration'. Jun 28, 2012 'Local Area Connection doesn't have a valid IP configuration', and then we are disconnected from the internet. We both can get back on pretty quickly by using the troubleshoot option on our desktops network button on the taskbar, however we'd like to know how to completely eradicate the disconnects as we both game online. We are using a Telus router which we received around a month ago.
My brother is connected wirelessly and I am hardwired in. We are both using Windows 7 with newer PC's (within the past year). Neither of us have a clue about networking so we are totally blanked on what settings to tweak to fix this issue, especially since it's not exclusively wireless or wired-in. Dec 2, 2012 I have a desktop PC using Windows 7 Pro. And a Airlink N 150 Mini USB wireless adapter. My 2Wire modem/router from AT&T was failing to stay connected and was replaced today with a Netgear 7550 modem/router from AT&T.
I installed the Netgear 7550 and am able to access the internet with my Asus Laptop, my LG Thrill phone, and my Samsung Galaxy 2 tablet with no problems. However, my Desktop cannot connect to the internet and the Window Network diagnostics returned the following message: Network Connection doesn't have a valid IP configuration. How do I go about connecting my desktop to the Netgear modem/router so that I have access to the internet? By the way I am able to connect to the internet using an ethernet cable and a LAN connection.
Hi everyone, I have some questions regarding ATM and DSL. Please explain my questions in a basic language. I have seen many configurations of DSL done on ATM interfaces.
1- DSL is related to ATM? 2- Does the service provider have also ATM interface and ATM network and what is the span of the ATM network.
It spans before internet gateway? 3-ATM cells are 53 byte, where as IP packets are 1500. How IP network works in this case (Going through DSL and ATM). 4- we can assign ip on ATM interface. How it works?
ATM has its own physical address. Hi Philip, 1- DSL is related to ATM? While DSL is primarily a physical layer technology, there are a few framing formats of choice that are carried over the DSL physical link signalling, and ATM is one of them. ADSL makes heavy use of ATM framing.
VDSL service is sometimes provided using Ethernet framing. The choice of ATM for DSL was logical because at the time DSL was an emerging technology, ATM was relatively popular with service providers.
Among other things, it allowed the provider to treat each DSL customer as if connected through a dedicated point-to-point 'connection' - in ATM, it is called the virtual circuit. Every customer had its own virtual circuit, so accounting, billing, etc. Was relatively easy to apply on virtual circuits independently. Also, because these virtual circuits never 'leaked into each other' in the provider's network, customers were perfectly isolated. 2- Does the service provider have also ATM interface and ATM network and what is the span of the ATM network.
It spans before internet gateway? Originally, yes. The ATM network was contiguous - it started at the customer's DSL interface, continued through the DSLAM and through the service provider's network (in fact, the service provider's network was based on ATM) up to the BRAS where the customer's packets were first inspected and either kept in the same service provider's network, or tunneled away to a different internet service provider.
Nowadays, ATM is not used anymore inside service provider's networks. While DSLAMs still need to speak ATM to customer's DSL modems and routers, they no longer use ATM on the interfaces toward the service provider's network. Instead, today's DSLAMs can use technologies such as MPLS pseudowires or Layer2 Tunneling Protocol to carry user data and direct it toward a BRAS. 3-ATM cells are 53 byte, where as IP packets are 1500. How IP network works in this case (Going through DSL and ATM).
IP packets are chopped up to pieces of at most 48 bytes (this is the size of the payload portion of an ATM cell) and are carried in multiple ATM cells. ATM actually uses a so-called ATM Adaptation Layer, or AAL, to assist in fragmenting the IP packets and putting them back together. There were multiple AAL types defined in an ATM network; DSL uses AAL5. You can read more about AAL5 here but it is admittedly a fairly involved reading: In original DSL deployments where the entire service provider network was ATM-based, IP packets became chopped and put piece-by-piece into individual ATM cells on the customer's DSL modem, proceeded in this form through the DSLAM and the service provider network to the BRAS where they were reassembled again. In today's networks, IP packets are still put piece-by-piece into ATM frames on customer DSL modems/routers, but based on DSLAM capabilities, they may be reassembled right at the DSLAM and carried over the service provider's network using any suitable technology currenly used - Ethernet, MPLS, L2TP. There is no ATM network anymore between the DSLAM and the BRAS.
4- we can assign ip on ATM interface. How it works? ATM has its own physical address. Addressing in ATM is a complex issue because on the ATM layer, there is the VPI/VCI addressing, and if we implemented the entire ATM stack including the higher protocols, we would also be using so-called NSAP addressing.
However, the relation between an IP address and a VPI/VCI is somewhat similar to the relation between an IP address configured on an Ethernet interface, and the interface's MAC address. With ATM interface, the IP address is independent of the whole ATM underneath. However, what allows other stations to talk to this IP address is the VPI/VCI configured on the ATM interface, that makes a specific virtual circuit to be processed by this interface and thus reach this IP address. If this ATM interface was used to reach multiple other stations over the ATM network, each of these stations would sit on a different virtual circuit with a different VPI/VCI combination. In the simplest case, you would need to define a mapping of all remote IP addresses onto the specific VPI/VCI combinations that identify virtual circuits going to these respective remote IP hosts. More complex environments used dynamic helper protocols to set up these mappings automatically. Please feel welcome to ask further!
Best regards, Peter. Hi Philip, I apologize for this late reply. It's been a busy week. 1- Originally, can I compare ATM with TCP/IP? You said physical layer of ATM can be DSL?
ATM does not have its own physical and transport and application layers? It is really difficult to exactly compare TCP/IP to ATM because they have been developed in very different environments with very different goals. Even though ATM itself has a fairly complex reference model consisting of 4 layers plus additional planes, it was most often treated just like a (sophisticated) data link layer technology. To TCP/IP, an ATM network was simply an OSI Layer1+2 technology. It is difficult to place or map ATM onto OSI model because, depending on the way it was deployed and perceived, it could be seen either as Layer1+2 (physical + data-link layer) or Layer1+2+3 (up to network layer) technology. ATM provides virtual circuits between attached hosts, allowing them to talk to each other directly as immediate neighbors, and this would be exactly what OSI Layer2 does.
However, ATM also had its own addressing model and was capable of searching for best paths between any two end hosts, which is a Layer3 function. The ATM addressing was derived either from ITU-T E.164 telephone numbering plan (for public networks), or from ISO NSAP addressing (also called ATM End System Address, AESA, for private networks). If the entire internet was based on ATM and used ATM addressing, we would not need IP anymore, and we would be placing TCP/UDP/etc. Segments directly into ATM cells, bypassing IP entirely. So from this point of view, ATM was also capable of running as a Layer3 technology. Because it is the style of deploying ATM that has an impact whether ATM will be reduced to Layer2 or Layer3 services, it is so difficult to state with clarity whether ATM is Layer2 or Layer3 technology.
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In any case, ATM had numerous physical layer implementations. Check out for a list of them, and notice that there are different speeds and even different interface types - for LAN, usually, 25 Mbps and 155 Mbps were standardized, while for WAN interfaces (T1, E1, T3, DS1, etc.), there was a multitude of different speeds. With specific regard to DSL, DSL is just another physical layer to ATM. As you are asking about the layers ATM does or does not have, let's check out the ATM reference model from the: ATM has its physical layer called PHY in many variants. Then there is the ATM layer that is roughly equivalent to the data-link layer in that it concerns with carrying 'frames' called ATM cells between attached devices. Above the ATM layer is the ATM Adaptation Layer, also called AAL, that governs all processes related to segmentation and reassembly of IP packets and their contents into ATM cells.
There were 6 AAL types in total (AAL0 through AAL5) for different types of traffic having different quality of service requirements. Out of these, DSL uses AAL5 which is arguably the simplest one. Our common networks and data-link layer technologies do not usually have a layer similar to AAL, but because the operations of AAL are so closely tied to the process of carrying useful data in ATM cells, AAL and ATM together provide services we're used to seeing in the data-link layer, and that is what is also suggested in the picture above. ATM did not in general specify higher layer protocols, so you don't see a network/transport/session/presentation/app layer in this model.
It simply has the 4th layer saying 'higher protocols', and that's where all higher protocols are. 2- How about PPPOA? It is IP over PPP over ATM over DSL? Why do we need to set MTU 1500 in PPPOA?
How do you relate it to IP packet and PPP frame and ATM cells? This is an extensive question and requires lots of explaining.
ATM - as a technology - can provide a virtual circuit between a subscriber and his service provider, but there is a lack of other features a service provider needs to do: authenticating the subscriber, performing the accounting, negotiating what higher protocols will be carried over the virtual circuit (such as IPv4 or IPv6), what settings should those higher protocols use, etc. The virtual circuit provided by ATM was just a raw data conduit, and some other protocol offering all these services was required to carry customer's data over this conduit. PPP was the natural choice here. It provides easy framing, authentication, accounting properties, it is able to carry multiple packet types itself, it provides mechanisms to negotiate which higher level protocols will be used and how they should be configured, so from this point of view, it was just perfect. However, there are different ways of carrying PPP frames over ATM circuits, and this causes considerable confusion. It is absolutely possible for a DSL router to receive IP packets from an attached LAN, encapsulate them into PPP frames and hand them over to the ATM/DSL interface. This ATM/DSL interface will encapsulate the PPP frames into an AAL5 datagram, chop it into ATM cells and send them over the DSL link.
This mode of operation is called PPP-over-ATM, or PPPoA, and is based on sending PPP frames right down the ATM/DSL interface. Contrary to what you said, PPPoA does not require modifying the DSL's interface MTU. AAL5 is capable of carrying (segmenting and reassembling) upper-layer datagrams of up to roughly 64 KiB which is far beyond the usual IP packet sizes. With PPPoA, there are absolutely no MTU issues.
The use of PPPoA poses a very strong requirement: It assumes that the device that originates PPP frames is also the endpoint of the ATM circuit (because it needs to feed the created PPP frames directly into the ATM circuit). This in turn means that the device running the PPP driver must be the very device with the DSL interface. For a modern DSL router, there's no problem in doing that because a DSL router has both a built-in DSL interface and also runs the PPP driver internally. However, in the beginnings of DSL, such integrated routers were extremely rare or did not exist at all. Also, there were no PCI or similar PC extension boards with DSL interfaces on them.
Instead, there were only external DSL modems that operated in an extremely simplified way: They had an Ethernet LAN interface, and a DSL WAN interface. Every Ethernet frame received on the LAN interface of a DSL modem was encapsulated in its entirety (including the headers) into AAL5, cut into ATM cells and sent out the DSL interface. In the opposite direction, data arriving in ATM cells on the DSL interface were reassembled into Ethernet frames and sent out the Ethernet interface. There was no routing, no NAT, no PPP, no additional processing involved on such a DSL modem at all. The DSL modem simply carried Ethernet frames to and from the service provider inside ATM cells. With the lack of any PPP driver in a DSL modem, the PPP driver had to be running on a normal PC using a common Ethernet interface. This posed another problem - if the PC can be connected to the DSL modem over an Ethernet interface only, how should the PPP frames created on the PC be delivered to the DSL modem so they can be ultimately forwarded to the service provider, and vice versa?
You probably guessed it - the PPP frames would get encapsulated into Ethernet frames, and the Ethernet frames would be then sent to the DSL modem, cut into pieces and carried inside ATM cells over the DSL link to the service provider. This approach is called PPP-over-Ethernet, or PPPoE. PPPoE was actually developed independently of ATM and DSL as a means of turning an Ethernet-based LAN into an overlay network of point-to-point PPP circuits between end hosts and an access concentrator, but it came very handy with DSL as well.
With PPPoE, therefore, the basic idea is that the PPP is running on the PC while the DSL modem only takes care of carrying the resulting Ethernet frames over the DSL ATM link as a series of ATM cells and their contents, and the PPP frames will be carried inside the Ethernet frames. However, because Ethernet frames can carry at most 1500 bytes in their payload, this payload now needs to accomodate the added PPP and PPPoE headers plus the original IP packet. PPPoE encapsulation consumes additional 8 bytes in its headers that need to fit into the Ethernet payload. This means that whatever IP packets are originated by the PC, they have to be smaller by 8 bytes than usual, otherwise, after the PPP+PPPoE headers are added, the resulting Ethernet frame would be oversized and considered invalid. This is the reason why PPPoE needs to have the interface MTU modified from 1500 to 1492 to accomodate the added 8 bytes of PPP+PPPoE headers - to prevent the resulting payload exceeding the maximum allowable size of 1500 bytes for an Ethernet frame. With today's modern DSL routers running PPP and PPPoE inside, you actually have a choice of configuring your DSL connection as PPPoA (direct PPP into ATM without the intermediary Ethernet encapsulation), or PPPoE. PPPoA is superior to PPPoE in terms of lesser overhead and no MTU issues.
However, whether you can use either PPPoE or PPPoA depends on your service provider; some of them support both modes while others support only one of these and you need to discuss with your service provider which mode should be used. It may come off as surprising to learn that even with integrated DSL routers using their built-in DSL interface, running DSL in PPPoE mode will cause every IP packet routed over the DSL link to be encapsulated in Ethernet+PPPoE+PPP headers even though there is no Ethernet link involved on the WAN side. This is, however, done to meet the provider's expectations.
Whenever PPPoE is used, the service provider expects that all data coming in from subscribers of the ATM virtual circuits are encapsulated in Ethernet+PPPoE+PPP frames. The service provider does not care where does the subscriber run his PPP driver - whether it is on his PC or on his integrated router. This gives the service provider the flexibility to communicate in the same way with any kind of customer, either those using simple DSL modems and running PPP software on their PCs, or those using integrated DSL routers.
So to sum it up:. PPPoA encapsulates PPP frames right into ATM cells (after being handled by AAL5). There are no MTU issues with PPPoA and no MTU modification is required. However, this mode requires that PPP software must be run on the same device that has the DSL interface installed. PPPoE encapsulates PPP frames into Ethernet frames plus additional PPPoE headers (to provide specific PPPoE operations; I'm not going to discuss them at this point), and the Ethernet frames are subsequently AAL5-encapsulated and carried in ATM cells. Because the Ethernet payload size is limited to 1500 bytes, the resulting PPPoE+PPP+IP datagram must not exceed 1500 bytes, and with PPPoE+PPP consuming 8 bytes, the maximum size of IP packets needs to be decreased to 1492 bytes.
PPPoE allows the user to run PPP software on his PC and use a simple DSL modem, or a DSL router configured in bridged mode, to communicate with the service provider. More complex environments used dynamic helper protocols to set up these mappings automatically. That protocol is NHRP? Yes, among others.
There were multiple protocols involved in ATM that dealt with addressing: ATMARP, NHRP, plus helper protocols such as ILMI and PNNI. Best regards, Peter. Hi Philip, 1- DSL is related to ATM? While DSL is primarily a physical layer technology, there are a few framing formats of choice that are carried over the DSL physical link signalling, and ATM is one of them. ADSL makes heavy use of ATM framing. VDSL service is sometimes provided using Ethernet framing. The choice of ATM for DSL was logical because at the time DSL was an emerging technology, ATM was relatively popular with service providers.
Among other things, it allowed the provider to treat each DSL customer as if connected through a dedicated point-to-point 'connection' - in ATM, it is called the virtual circuit. Every customer had its own virtual circuit, so accounting, billing, etc. Was relatively easy to apply on virtual circuits independently. Also, because these virtual circuits never 'leaked into each other' in the provider's network, customers were perfectly isolated.
2- Does the service provider have also ATM interface and ATM network and what is the span of the ATM network. It spans before internet gateway? Originally, yes. The ATM network was contiguous - it started at the customer's DSL interface, continued through the DSLAM and through the service provider's network (in fact, the service provider's network was based on ATM) up to the BRAS where the customer's packets were first inspected and either kept in the same service provider's network, or tunneled away to a different internet service provider. Nowadays, ATM is not used anymore inside service provider's networks.
While DSLAMs still need to speak ATM to customer's DSL modems and routers, they no longer use ATM on the interfaces toward the service provider's network. Instead, today's DSLAMs can use technologies such as MPLS pseudowires or Layer2 Tunneling Protocol to carry user data and direct it toward a BRAS. 3-ATM cells are 53 byte, where as IP packets are 1500. How IP network works in this case (Going through DSL and ATM). IP packets are chopped up to pieces of at most 48 bytes (this is the size of the payload portion of an ATM cell) and are carried in multiple ATM cells.
ATM actually uses a so-called ATM Adaptation Layer, or AAL, to assist in fragmenting the IP packets and putting them back together. There were multiple AAL types defined in an ATM network; DSL uses AAL5. You can read more about AAL5 here but it is admittedly a fairly involved reading: In original DSL deployments where the entire service provider network was ATM-based, IP packets became chopped and put piece-by-piece into individual ATM cells on the customer's DSL modem, proceeded in this form through the DSLAM and the service provider network to the BRAS where they were reassembled again. In today's networks, IP packets are still put piece-by-piece into ATM frames on customer DSL modems/routers, but based on DSLAM capabilities, they may be reassembled right at the DSLAM and carried over the service provider's network using any suitable technology currenly used - Ethernet, MPLS, L2TP.
There is no ATM network anymore between the DSLAM and the BRAS. 4- we can assign ip on ATM interface.
How it works? ATM has its own physical address. Addressing in ATM is a complex issue because on the ATM layer, there is the VPI/VCI addressing, and if we implemented the entire ATM stack including the higher protocols, we would also be using so-called NSAP addressing. However, the relation between an IP address and a VPI/VCI is somewhat similar to the relation between an IP address configured on an Ethernet interface, and the interface's MAC address. With ATM interface, the IP address is independent of the whole ATM underneath. However, what allows other stations to talk to this IP address is the VPI/VCI configured on the ATM interface, that makes a specific virtual circuit to be processed by this interface and thus reach this IP address. If this ATM interface was used to reach multiple other stations over the ATM network, each of these stations would sit on a different virtual circuit with a different VPI/VCI combination.
In the simplest case, you would need to define a mapping of all remote IP addresses onto the specific VPI/VCI combinations that identify virtual circuits going to these respective remote IP hosts. More complex environments used dynamic helper protocols to set up these mappings automatically.
Please feel welcome to ask further! Best regards, Peter. Hi Philip, I apologize for this late reply. It's been a busy week. 1- Originally, can I compare ATM with TCP/IP?
You said physical layer of ATM can be DSL? ATM does not have its own physical and transport and application layers? It is really difficult to exactly compare TCP/IP to ATM because they have been developed in very different environments with very different goals. Even though ATM itself has a fairly complex reference model consisting of 4 layers plus additional planes, it was most often treated just like a (sophisticated) data link layer technology.
To TCP/IP, an ATM network was simply an OSI Layer1+2 technology. It is difficult to place or map ATM onto OSI model because, depending on the way it was deployed and perceived, it could be seen either as Layer1+2 (physical + data-link layer) or Layer1+2+3 (up to network layer) technology. ATM provides virtual circuits between attached hosts, allowing them to talk to each other directly as immediate neighbors, and this would be exactly what OSI Layer2 does. However, ATM also had its own addressing model and was capable of searching for best paths between any two end hosts, which is a Layer3 function. The ATM addressing was derived either from ITU-T E.164 telephone numbering plan (for public networks), or from ISO NSAP addressing (also called ATM End System Address, AESA, for private networks). If the entire internet was based on ATM and used ATM addressing, we would not need IP anymore, and we would be placing TCP/UDP/etc.
Segments directly into ATM cells, bypassing IP entirely. So from this point of view, ATM was also capable of running as a Layer3 technology. Because it is the style of deploying ATM that has an impact whether ATM will be reduced to Layer2 or Layer3 services, it is so difficult to state with clarity whether ATM is Layer2 or Layer3 technology. In any case, ATM had numerous physical layer implementations. Check out for a list of them, and notice that there are different speeds and even different interface types - for LAN, usually, 25 Mbps and 155 Mbps were standardized, while for WAN interfaces (T1, E1, T3, DS1, etc.), there was a multitude of different speeds. With specific regard to DSL, DSL is just another physical layer to ATM. As you are asking about the layers ATM does or does not have, let's check out the ATM reference model from the: ATM has its physical layer called PHY in many variants.
Then there is the ATM layer that is roughly equivalent to the data-link layer in that it concerns with carrying 'frames' called ATM cells between attached devices. Above the ATM layer is the ATM Adaptation Layer, also called AAL, that governs all processes related to segmentation and reassembly of IP packets and their contents into ATM cells. There were 6 AAL types in total (AAL0 through AAL5) for different types of traffic having different quality of service requirements. Out of these, DSL uses AAL5 which is arguably the simplest one.
Our common networks and data-link layer technologies do not usually have a layer similar to AAL, but because the operations of AAL are so closely tied to the process of carrying useful data in ATM cells, AAL and ATM together provide services we're used to seeing in the data-link layer, and that is what is also suggested in the picture above. ATM did not in general specify higher layer protocols, so you don't see a network/transport/session/presentation/app layer in this model. It simply has the 4th layer saying 'higher protocols', and that's where all higher protocols are. 2- How about PPPOA? It is IP over PPP over ATM over DSL? Why do we need to set MTU 1500 in PPPOA? How do you relate it to IP packet and PPP frame and ATM cells?
This is an extensive question and requires lots of explaining. ATM - as a technology - can provide a virtual circuit between a subscriber and his service provider, but there is a lack of other features a service provider needs to do: authenticating the subscriber, performing the accounting, negotiating what higher protocols will be carried over the virtual circuit (such as IPv4 or IPv6), what settings should those higher protocols use, etc. The virtual circuit provided by ATM was just a raw data conduit, and some other protocol offering all these services was required to carry customer's data over this conduit. PPP was the natural choice here. It provides easy framing, authentication, accounting properties, it is able to carry multiple packet types itself, it provides mechanisms to negotiate which higher level protocols will be used and how they should be configured, so from this point of view, it was just perfect.
However, there are different ways of carrying PPP frames over ATM circuits, and this causes considerable confusion. It is absolutely possible for a DSL router to receive IP packets from an attached LAN, encapsulate them into PPP frames and hand them over to the ATM/DSL interface.
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This ATM/DSL interface will encapsulate the PPP frames into an AAL5 datagram, chop it into ATM cells and send them over the DSL link. This mode of operation is called PPP-over-ATM, or PPPoA, and is based on sending PPP frames right down the ATM/DSL interface. Contrary to what you said, PPPoA does not require modifying the DSL's interface MTU. AAL5 is capable of carrying (segmenting and reassembling) upper-layer datagrams of up to roughly 64 KiB which is far beyond the usual IP packet sizes. With PPPoA, there are absolutely no MTU issues. The use of PPPoA poses a very strong requirement: It assumes that the device that originates PPP frames is also the endpoint of the ATM circuit (because it needs to feed the created PPP frames directly into the ATM circuit).
This in turn means that the device running the PPP driver must be the very device with the DSL interface. For a modern DSL router, there's no problem in doing that because a DSL router has both a built-in DSL interface and also runs the PPP driver internally. However, in the beginnings of DSL, such integrated routers were extremely rare or did not exist at all. Also, there were no PCI or similar PC extension boards with DSL interfaces on them. Instead, there were only external DSL modems that operated in an extremely simplified way: They had an Ethernet LAN interface, and a DSL WAN interface. Every Ethernet frame received on the LAN interface of a DSL modem was encapsulated in its entirety (including the headers) into AAL5, cut into ATM cells and sent out the DSL interface. In the opposite direction, data arriving in ATM cells on the DSL interface were reassembled into Ethernet frames and sent out the Ethernet interface.
There was no routing, no NAT, no PPP, no additional processing involved on such a DSL modem at all. The DSL modem simply carried Ethernet frames to and from the service provider inside ATM cells.
With the lack of any PPP driver in a DSL modem, the PPP driver had to be running on a normal PC using a common Ethernet interface. This posed another problem - if the PC can be connected to the DSL modem over an Ethernet interface only, how should the PPP frames created on the PC be delivered to the DSL modem so they can be ultimately forwarded to the service provider, and vice versa? You probably guessed it - the PPP frames would get encapsulated into Ethernet frames, and the Ethernet frames would be then sent to the DSL modem, cut into pieces and carried inside ATM cells over the DSL link to the service provider. This approach is called PPP-over-Ethernet, or PPPoE. PPPoE was actually developed independently of ATM and DSL as a means of turning an Ethernet-based LAN into an overlay network of point-to-point PPP circuits between end hosts and an access concentrator, but it came very handy with DSL as well. With PPPoE, therefore, the basic idea is that the PPP is running on the PC while the DSL modem only takes care of carrying the resulting Ethernet frames over the DSL ATM link as a series of ATM cells and their contents, and the PPP frames will be carried inside the Ethernet frames.
However, because Ethernet frames can carry at most 1500 bytes in their payload, this payload now needs to accomodate the added PPP and PPPoE headers plus the original IP packet. PPPoE encapsulation consumes additional 8 bytes in its headers that need to fit into the Ethernet payload. This means that whatever IP packets are originated by the PC, they have to be smaller by 8 bytes than usual, otherwise, after the PPP+PPPoE headers are added, the resulting Ethernet frame would be oversized and considered invalid. This is the reason why PPPoE needs to have the interface MTU modified from 1500 to 1492 to accomodate the added 8 bytes of PPP+PPPoE headers - to prevent the resulting payload exceeding the maximum allowable size of 1500 bytes for an Ethernet frame. With today's modern DSL routers running PPP and PPPoE inside, you actually have a choice of configuring your DSL connection as PPPoA (direct PPP into ATM without the intermediary Ethernet encapsulation), or PPPoE. PPPoA is superior to PPPoE in terms of lesser overhead and no MTU issues. However, whether you can use either PPPoE or PPPoA depends on your service provider; some of them support both modes while others support only one of these and you need to discuss with your service provider which mode should be used.
It may come off as surprising to learn that even with integrated DSL routers using their built-in DSL interface, running DSL in PPPoE mode will cause every IP packet routed over the DSL link to be encapsulated in Ethernet+PPPoE+PPP headers even though there is no Ethernet link involved on the WAN side. This is, however, done to meet the provider's expectations. Whenever PPPoE is used, the service provider expects that all data coming in from subscribers of the ATM virtual circuits are encapsulated in Ethernet+PPPoE+PPP frames. The service provider does not care where does the subscriber run his PPP driver - whether it is on his PC or on his integrated router. This gives the service provider the flexibility to communicate in the same way with any kind of customer, either those using simple DSL modems and running PPP software on their PCs, or those using integrated DSL routers. So to sum it up:. PPPoA encapsulates PPP frames right into ATM cells (after being handled by AAL5).
There are no MTU issues with PPPoA and no MTU modification is required. However, this mode requires that PPP software must be run on the same device that has the DSL interface installed. PPPoE encapsulates PPP frames into Ethernet frames plus additional PPPoE headers (to provide specific PPPoE operations; I'm not going to discuss them at this point), and the Ethernet frames are subsequently AAL5-encapsulated and carried in ATM cells. Because the Ethernet payload size is limited to 1500 bytes, the resulting PPPoE+PPP+IP datagram must not exceed 1500 bytes, and with PPPoE+PPP consuming 8 bytes, the maximum size of IP packets needs to be decreased to 1492 bytes. PPPoE allows the user to run PPP software on his PC and use a simple DSL modem, or a DSL router configured in bridged mode, to communicate with the service provider. More complex environments used dynamic helper protocols to set up these mappings automatically. That protocol is NHRP?
Yes, among others. There were multiple protocols involved in ATM that dealt with addressing: ATMARP, NHRP, plus helper protocols such as ILMI and PNNI. Best regards, Peter.