RE: Hello everybody
On Mon, 2005-02-14 at 16:36 +, Rui Campos wrote: > Hi Dan, > > Thanks for your quick answers! > > I am wondering whether "Network Manager" could manage such a switch in a > transparent way for the applications. Anyway, you already answered this > question in our comprehensive explanation. Thanks for that! Without something like Mobile-IP, I think it's impossible not to break existing IP connections. Instead, we need to make applications aware of the network events that NM broadcasts, like "network now up" and "network now down". In the gaim example, when gaim receives the "down" signal, it should disconnect its connections, and wait for the "up" signal. If it receives that signal within, say, 10 seconds, it should reconnect the connections that were broken by the "down" event. If not, perhaps it should display the "You were disconnected" dialog. Its a hard problem, because there is no guarantee how long the network will stay "down". The user may be searching for the correct WEP key or passphrase, may be away from their desk when the passphrase dialog pops up, or they may have traveled to an area where no network connection is possible. Applications have to take into account that the network does not have to come back up immediately. Really, they have to be anything other than incompetent about network state, which is what they are now. Evolution, for example, has online/offline modes, but it expects the network to be available when you choose "offline", because it tells each of its backends (IMAP, POP3, etc) to move to offline mode where each backend may do something like cache mail. That takes time. In the NM model, you don't have any time since the network has already gone away. > In my PhD thesis (I just started four months ago :-)), I am looking for > mobility and multihoming support in an integrated fashion, in a > heterogeneous environment. The kind of mobility support I am interested in > is similar to that provided by Mobile IP framework, i.e. changes in network > access are transparent to transport and application layer. > > P.S. By the way, have you ever considered some kind of synergy between > Mobile IP and such a Network Manager? I had talked about it with one of our other guys here quite a while back. I just went and read http://www.computer.org/internet/v2n1/perkins.htm to brush up a bit. It appears that this would need both kernel-side and user-space-side components. First, on the kernel side, we need to ensure that the encapsulated packets from the home agent are decapsulated correctly and delivered to the upper layers of the TCP stack with the correct home IP address intact. That seems like a job of the network stack or of iptables, which can rewrite packets depending on certain rules. Of course, since these rules would be dynamic, iptables might need modification. But certainly something on the kernel side needs it. On the user-space side, where NM lives, we'd need a couple more things. First, when we move to new networks, we would need to broadcast a request for a new "care-of" address. Once the reply was received, NM would need to notify the kernel of the new care-of address so it could rewrite the packets correctly. NM would then need to ensure that the care-of address works correctly, then notify the home-agent of the new care-of address. NM would then need to set up the IP-within-IP tunnel. Once that is done, the network is more or less "up" and applications could send and receive data with no interruption. In an upcoming rewrite of NM (starting this spring), I hope to make the NM architecture more modular to support more services and devices. For example, the Mobile-IP bits don't really need to be a core part of NM, but could be a service that NM depends on and makes requests of. Something like "Hi, Mobile-IP, please get a new care-of address and tell me when you're done." The mobile IP bits don't need to know which network you're connecting to (ie wired, wireless, whatever), they just need to know which particular network interface to start operating on. NM doesn't need to know about the details of the Mobile-IP negotiations, just when they either complete successfully, or fail, so that NM can announce the network as "up" or switch the connection to something else. As long as the kernel facilities are there to support Mobile-IP, the packet encapsulation/decapsulation, and delivery of packets with the correct "Home" IP address to the application layers, I think this isn't a hard problem to solve. Dan ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
RE: Hello everybody
Hi Dan, Thanks for your quick answers! I am wondering whether "Network Manager" could manage such a switch in a transparent way for the applications. Anyway, you already answered this question in our comprehensive explanation. Thanks for that! In my PhD thesis (I just started four months ago :-)), I am looking for mobility and multihoming support in an integrated fashion, in a heterogeneous environment. The kind of mobility support I am interested in is similar to that provided by Mobile IP framework, i.e. changes in network access are transparent to transport and application layer. I hope I have answered your question! BR, Rui Campos P.S. By the way, have you ever considered some kind of synergy between Mobile IP and such a Network Manager? -Original Message- From: Dan Williams [mailto:[EMAIL PROTECTED] Sent: segunda-feira, 14 de Fevereiro de 2005 16:18 To: Rui Campos Cc: networkmanager-list@gnome.org Subject: Re: Hello everybody On Mon, 2005-02-14 at 15:53 +, Rui Campos wrote: > I am doing my PhD in the networking area (particularly in Mobile > Networks) and I am very interested in this Network Manager, you have > been designing and implementing. Can anybody tell me a bit more about > it? For example, are you considering things like Mobility, i.e. > always-on connectivity service? In the web page of the project, I > think that you don't refer explicitly to such a feature! Hi, Great to hear you're interested. The point of NetworkManager was to _attempt_ to provide a network connection no matter where you are. Eventually, we hope to support things like Bluetooth, GPRS, and probably ISDN and modems as well. The auto-switching capability is a large part of this, for example: if you've been using the wireless network, and you plug in the cable, NM will switch your connection to the cable. When you unplug (or undock) it will switch to wireless. NM attempts to be as automatic as possible. Some issues that get in the way are likely to be solved in the future, for example not all wired cards support link-detection right now, and NM just ignores those cards unless you explicitly tell it to switch to them. Furthermore, many wireless cards don't report correct signal quality, making it impossible to pick wireless base stations based on their quality or proximity. This stuff slowly gets fixed in the kernel though. Many applications (like gaim or evolution) also aren't aware of network changes, so when NM switches the network connection gaim pops up a "you've been disconnected" dialog. Support for NetworkManager will gradually work its way into these apps. We don't support WPA or other types of authentication besides WEP right now, but that will hopefully be fixed in the coming months. Again, that needs to be seamless so the user is minimally interrupted. Could you explain a bit more about the areas of mobility that you're interested in, or some of the things you're looking at for your thesis? Thanks Dan ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
Re: Hello everybody
On Mon, 2005-02-14 at 15:53 +, Rui Campos wrote: > I am doing my PhD in the networking area (particularly in Mobile > Networks) and I am very interested in this Network Manager, you have > been designing and implementing. Can anybody tell me a bit more about > it? For example, are you considering things like Mobility, i.e. > always-on connectivity service? In the web page of the project, I > think that you donât refer explicitly to such a feature! Hi, Great to hear you're interested. The point of NetworkManager was to _attempt_ to provide a network connection no matter where you are. Eventually, we hope to support things like Bluetooth, GPRS, and probably ISDN and modems as well. The auto-switching capability is a large part of this, for example: if you've been using the wireless network, and you plug in the cable, NM will switch your connection to the cable. When you unplug (or undock) it will switch to wireless. NM attempts to be as automatic as possible. Some issues that get in the way are likely to be solved in the future, for example not all wired cards support link-detection right now, and NM just ignores those cards unless you explicitly tell it to switch to them. Furthermore, many wireless cards don't report correct signal quality, making it impossible to pick wireless base stations based on their quality or proximity. This stuff slowly gets fixed in the kernel though. Many applications (like gaim or evolution) also aren't aware of network changes, so when NM switches the network connection gaim pops up a "you've been disconnected" dialog. Support for NetworkManager will gradually work its way into these apps. We don't support WPA or other types of authentication besides WEP right now, but that will hopefully be fixed in the coming months. Again, that needs to be seamless so the user is minimally interrupted. Could you explain a bit more about the areas of mobility that you're interested in, or some of the things you're looking at for your thesis? Thanks Dan ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
Hello everybody
Hi all, I have just joined the list! Hello everybody! I am doing my PhD in the networking area (particularly in Mobile Networks) and I am very interested in this Network Manager, you have been designing and implementing. Can anybody tell me a bit more about it? For example, are you considering things like Mobility, i.e. always-on connectivity service? In the web page of the project, I think that you don’t refer explicitly to such a feature! Thanks in advance for your answers! Best Regards, Rui Campos ___ NetworkManager-list mailing list NetworkManager-list@gnome.org http://mail.gnome.org/mailman/listinfo/networkmanager-list
