Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
[EMAIL PROTECTED] wrote: A similar problem would be created if a web server relied on DNS that was only hosted on servers in New Orleans. Do you (or somebody) know of recent numbers of what percentage of domains have all their DNS servers in; a) same subnet b) same AS c) same geographical zone (faultline, floodplain, coastline, etc.) Obviously if everything served by the DNS is co-located in the same failed facility, it does not matter that much if the names resolve to IP addresses which are unreachable anyway. Pete
Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
I've had several reports that cell phone users who can't make *or* receive calls are successfully sending *and* receiving SMS. It could be that the problem is one of not enough cell channels and working phone circuits for all the phone calls people want to make, but that the SMS channel is not overloaded and thus SMS traffic can zip on thru (when the cell has power and can reach a working cell tower). This was my personal experience during the July 7th terrorist attacks in London. I couldn't make or receive voice calls but SMS did get through both incoming and outgoing. However the delivery of SMS messages was sometimes delayed by as much as an hour. SMS takes far less network bandwidth than voice calls. Originally it was implemented as part of the control network of GSM (rather like SS7) but I believe that most carriers now simply use IP networks to carry their SMS traffic. By now it has become clear that the response to the New Orleans disaster has been completely screwed up because of lack of reliable communications in and out of the city. There are tons of food, water, medical supplies and personnel hung up on edge of the city because no-one seems to know what is needed, where it is needed, how to get it there, etc. --Michael Dillon
RE: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
SMS is all IP these days. Look at mBlox for more data. Others like them. The real key to SMS (and IP) that makes VoIP and PSTN so different is SMS does not need to be real time, and it does not have to be in order (i.e. packet 2 does not have to come after packet 3 etc.). It delivers whatever data it can when it can Thus extremely low bandwidth required (1 bit per second would take a long time to get the message through, but it would make it) -Original Message- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of [EMAIL PROTECTED] Sent: Friday, September 02, 2005 5:57 AM To: nanog@merit.edu Subject: Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake I've had several reports that cell phone users who can't make *or* receive calls are successfully sending *and* receiving SMS. It could be that the problem is one of not enough cell channels and working phone circuits for all the phone calls people want to make, but that the SMS channel is not overloaded and thus SMS traffic can zip on thru (when the cell has power and can reach a working cell tower). This was my personal experience during the July 7th terrorist attacks in London. I couldn't make or receive voice calls but SMS did get through both incoming and outgoing. However the delivery of SMS messages was sometimes delayed by as much as an hour. SMS takes far less network bandwidth than voice calls. Originally it was implemented as part of the control network of GSM (rather like SS7) but I believe that most carriers now simply use IP networks to carry their SMS traffic. By now it has become clear that the response to the New Orleans disaster has been completely screwed up because of lack of reliable communications in and out of the city. There are tons of food, water, medical supplies and personnel hung up on edge of the city because no-one seems to know what is needed, where it is needed, how to get it there, etc. --Michael Dillon
Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
On Thu, Sep 01, 2005 at 09:41:40AM -0700, jc dill wrote: It is sometimes the case in disasters that people from inside can call out but that people from outside can't call in because the circuits into the disaster area become overloaded. This would hold true especially in the case where many people in the disaster area have no access to working phones, so those with working phones can easily get a free outbound circuit - meanwhile frantic friends and family clog up the incoming circuits trying to reach phones that are out of service or people who simply aren't near the phone and who can't answer but those calls still tie up circuits each time they are attempted. It could also be deliberate; one comment I've heard in relation to emergency communications is that one message out can stop eight messages back in. If someone inside the affected area can speak to a friend/family member to say that they're ok, and they're in shelter X in town Y, that friend/family member can/will tell the others others concerned about the disaster victim this info, freeing up communication resources into the affected area. Prioritizing outgoing calls over incoming calls might help with this. Bob
Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
But then, people don't really care about this, as cell is in the exact same boat and huge numbers of people rely on just their cell phone and no longer have a fixed line (in Europe at least). I have read accounts that suggest that cellphone subscribers from New Orleans only have one way service. In other words, if you left New Orleans with your cellphone then you can make outgoing calls but no-one can call you. I don't know how widespread this is, but knowing that there has to be an SS7 switch in New Orleans directing those incoming calls to your new location, I can imaging that loss of such a switch would create problems. A similar problem would be created if a web server relied on DNS that was only hosted on servers in New Orleans. --Michael Dillon
Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
[EMAIL PROTECTED] wrote: But then, people don't really care about this, as cell is in the exact same boat and huge numbers of people rely on just their cell phone and no longer have a fixed line (in Europe at least). I have read accounts that suggest that cellphone subscribers from New Orleans only have one way service. In other words, if you left New Orleans with your cellphone then you can make outgoing calls but no-one can call you. I don't know how widespread this is, but knowing that there has to be an SS7 switch in New Orleans directing those incoming calls to your new location, I can imaging that loss of such a switch would create problems. It is sometimes the case in disasters that people from inside can call out but that people from outside can't call in because the circuits into the disaster area become overloaded. This would hold true especially in the case where many people in the disaster area have no access to working phones, so those with working phones can easily get a free outbound circuit - meanwhile frantic friends and family clog up the incoming circuits trying to reach phones that are out of service or people who simply aren't near the phone and who can't answer but those calls still tie up circuits each time they are attempted. I've had several reports that cell phone users who can't make *or* receive calls are successfully sending *and* receiving SMS. It could be that the problem is one of not enough cell channels and working phone circuits for all the phone calls people want to make, but that the SMS channel is not overloaded and thus SMS traffic can zip on thru (when the cell has power and can reach a working cell tower). jc
Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
On Thu, 01 Sep 2005 08:48:04 +0300, Petri Helenius said: [EMAIL PROTECTED] wrote: It's clearly possible to find telco engineers with 5/10/15 years experience in running PSTN (might even find somebody with 40-50 years? :). It's possible to find network engineers with lots of BGP experience. Where do you find a senior engineer with 5+ years experience in enterprise-scale VoIP deployment? Deployable enterprise VoIP products existed in 1998. So it would be somebody who was there doing it back then? Goes 5+ with a margin. Yes, but I hear that both of the guys who actually *DEPLOYED* anything enterprise-wide in 1998 are happily employed and not available. pgpQYgDKA7sWw.pgp Description: PGP signature
Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
At the risk of replying to myself, The below article is about the core, not the edge Theres another article on Telecom's site relating to trials for edge IP equipment. So my take on the NZ situation was a bit warped. I do see a risk in the move toward IP systems at the edge. At the core is a different story to at least some degree. Twas also pointed out that British Telecom are heading down the same track as Telecom NZ, and their rollout should be completed earlier. I trust therefore that it has all been thought out in terms of robustness and the like. As was pointed out to me offlist, when the PSTN falls over, alternate-network based IP systems do have their merits - but I've always favoured the simple over the complex from a view of resilience. IP stuff has that many more layers to break? Operationally, natural disasters and the like do reveal our reliance on increasingly complex systems, with x number of additional dependencies that can take the service down. Of course, events like Katrina are fairly extreme, but in general, people should have some sort of fallback position. Its not a bad general rule. Mark. On Wed, 31 Aug 2005, Mark Foster wrote: Telecom New Zealand announced the other day their intention to do precisely this. In relatively short order we will replace the entire PSTN and be delivering all our services for customers over the IP network. That has the potential to reduce costs for customers and put a lot more control and flexibility in customers. hands, wherever they are . at home, at work or on the move.. From http://www.telecom-media.co.nz/releases_detail.asp?id=3223page=index I have to say I would usually agree with you - but it looks like I may not have a choice, going forward... The whole country to be migrated by 2012. The whole idea of not having POTS to fall back on doesn't sit well with me - As part of AREC we prepare for a situation where all other means have failed. Suddenly it seems so much more likely... ? Mark. On Tue, 30 Aug 2005, Fergie (Paul Ferguson) wrote: Me? I personally never trade my POTS for VoIP... - ferg -- Iljitsch van Beijnum [EMAIL PROTECTED] wrote: On 30-aug-2005, at 22:08, Fergie (Paul Ferguson) wrote: In this age of cheap commoditized consumer electronics and advanced mobile technology, why can't all the people of a city make contact during an emergency? Simple: it's too expensive. Keep this in mind when trading in your POTS service for VoIP service over the internet. Discounting the local loop which is often the same in both cases, POTS is extremely reliable while VoIP over the public internet, well, isn't. But apparently people that switch to VoIP don't mind the reduced likelihood of being able to make calls during the next large scale emergency.
Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
On 31-aug-2005, at 10:04, Mark Foster wrote: I do see a risk in the move toward IP systems at the edge. At the core is a different story to at least some degree. Twas also pointed out that British Telecom are heading down the same track as Telecom NZ, and their rollout should be completed earlier. I trust therefore that it has all been thought out in terms of robustness and the like. There are two types of VoIP: voice over a private, tightly controlled IP network, and voice over the public internet. Now obviously the latter is a risky proposition, as it imports all the limitations of the internet into the voice service. Apart from the fact that many parts of the internet aren't all that robust (but some are), this is a problem because voice and IP react differently to congestion collapse, which invariably happens to some degree in big emergencies. With IP, delays and packet loss build up, slowing everything down, but allowing many protocols to continue to work at a reduced rate. With PSTN, initiating calls starts failing more and more, but when you get through, you generally get to talk because you get a reserved piece of the scarce bandwidth. With VoIP, packet loss and delay eventually make the service useless. So VoIP fails harder than either traditional IP apps and PSTN. However, voice over a private network isn't entirely trouble-free, even though the private network can be designed such that congestion is a less fatal problem. And it does have the advantage that it allows IP routing protocols to route ongoing calls around failed parts of the network. On the other hand, in a circuit switched network you can do all kinds of interesting stuff (such as restarting all your control software) without breaking your sessions. We're only now seeing this in IP, and I think it's not really possible to reach the same levels with IP routing even in the long run. And then there is all this SIP stuff, which I'm (thankfully) only superficially familiar with, but never seemed particular robust to me. And voice over any kind of packet infrastructure introduces significant additional delays. I think in 10 years or so we'll realize that TDM isn't so bad after all.
Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
With VoIP, packet loss and delay eventually make the service useless. So VoIP fails harder than either traditional IP apps and PSTN. That is only in theory. In practice, during times of impending congestion collapse, IP network operators reconfigure the network to cope. For instance when DDoS is detected, people set up ACLs and trigger black hole routes. I think that it is possible for network operators to define an analogous action plan to stave off congestion collapse in an emergency situation. I'm not sure exactly what that action plan would look like, but I'm sure other list members will have plenty of good ideas. If you'll recall, just a few days ago people were talking about how they informally identified IP connectivity to emergency response sites so that those sites could be given priority in restoring service. We just need to sit down and talk these things over with our local emergency response organizations and learn where network operators can become part of the solution. On the other hand, in a circuit switched network you can do all kinds of interesting stuff (such as restarting all your control software) without breaking your sessions. We're only now seeing this in IP, and I think it's not really possible to reach the same levels with IP routing even in the long run. MPLS may have the edge here because you can have backup paths and fast reroute to keep traffic flowing if you have an orderly plan for rebooting routers. And voice over any kind of packet infrastructure introduces significant additional delays. Experience with the Inter-NOC phone system http://www.pch.net/inoc-dba/ seems to suggest otherwise. Some kinds of packet infrastructure only introduce insignificant delays. It would be interesting to know if any of the academics among us have studied the behavior of a SIP-based VoIP network during various types of failure and congestion scenarios. I suspect that problems will be mostly found under certain specific sets of conditions and if we know what those conditions are and how they impact voice services, then we can plan actions to mitigate the problems. One thing that IP network operators can do is throw bandwidth at a problem by shedding load, i.e. killing traffic that is deemed non-essential. This would free bandwidth for traffic that is deemed important. This has nothing to do with QoS per se becaus it can be implemented in many ways up to and including unplugging sites that generate non-essential traffic. All indications are that the next few decades will see an increased number of emergency situation like the tsunami, terror attacks in major cities, hurricanes, earthquakes. We have gotten very good at running the network through normal times, maybe we should now focus on how to keep it running through times of extreme stress. --Michael Dillon
Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
Iljitsch van Beijnum wrote: There are two types of VoIP: voice over a private, tightly controlled IP network, and voice over the public internet. Now obviously the latter is a risky proposition, as it imports all the limitations of the internet into the voice service. I'm not so sure; someone cuts an ISDN-30 into our building and the sky falls down. Someone cuts some fibre carrying IP and life (and communications) carry on .. Perhaps you've made a fair and good comment on the marurity of most off-the-shelf voip products or implementations. But the key, in my mind, is that VoIP across the internet, when done well, imports all of the opportunities of internet routing into voice service. -a
Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
--On August 31, 2005 2:03:01 PM +0100 [EMAIL PROTECTED] wrote: ... On the other hand, in a circuit switched network you can do all kinds of interesting stuff (such as restarting all your control software) without breaking your sessions. We're only now seeing this in IP, and I think it's not really possible to reach the same levels with IP routing even in the long run. MPLS may have the edge here because you can have backup paths and fast reroute to keep traffic flowing if you have an orderly plan for rebooting routers. Which does us no good in the case that we're close to the edge device and need to reboot the control plane of a nearby router. To me it seems Juniper and Cisco are both making huge steps in understanding this is necessary technology they can 'borrow' from telco's. You've a highly intelligent, but fairly decoupled control plane, with a fairly dumb, but largely automatic 'forwarding' or 'circuit fabric' plane being directed by the control plane. If the control plane takes a nap, the bottom end continues what it was doing until something (control plane coming back online, backup control plane doing takeover) tells it otherwise. No this isn't easily possible in most instances, even with just bare IP and with NAT it becomes really difficult because of the large amount of intelligence (relatively speaking) required to handle NAT. I should clarify that when I say NAT I mean PNAT and application/protocol specific NAT that requires more than just simple packet mangling. I think though, that eventually this will be commonplace, certainly in the core, and even really close to the edges. the M10i's approach this sort of resiliency. the T series and the larger M series also work like thisI think that the ONS' also are pushing on this (though admittedly aren't exactly IP...) Anyway, point is, that if you're right up close to the edge, MPLS may not matter, towards the core sure, where you're away from actual end connections and there's redundancy around you when you need to do a control plane restart. There will always be upgrades. Further there will always be other issues, however, in my mind atleast, today's networks are far more resilient and faster to heal than they've been in the past, atleast in IP PSTN...well...They're reliability king, until something unexpected happens. There were reports on here I believe it was even about call routing issues during this outage, not capacity type issues, simple lack of the systems ability to reconfigure and cope with loss of connectivity. There are places for both PSTN and IP though.
Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
On Wed, 31 Aug 2005 20:19:23 BST, Andy Davidson said: Perhaps you've made a fair and good comment on the marurity of most off-the-shelf voip products or implementations. But the key, in my mind, is that VoIP across the internet, when done well, imports all of the opportunities of internet routing into voice service. The crucial point being that when done well is something that you usually can't evaluate until it's too late. And there's maturity level for more than just products and implementations. It's clearly possible to find telco engineers with 5/10/15 years experience in running PSTN (might even find somebody with 40-50 years? :). It's possible to find network engineers with lots of BGP experience. Where do you find a senior engineer with 5+ years experience in enterprise-scale VoIP deployment? pgp8HAOS0l7C5.pgp Description: PGP signature
Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
On 31-aug-2005, at 21:19, Andy Davidson wrote: There are two types of VoIP: voice over a private, tightly controlled IP network, and voice over the public internet. Now obviously the latter is a risky proposition, as it imports all the limitations of the internet into the voice service. I'm not so sure; someone cuts an ISDN-30 into our building and the sky falls down. Yes, single homing sucks. Someone cuts some fibre carrying IP and life (and communications) carry on .. You can get your ISDN 30 over redundant fibers too, that's not the problem. Perhaps you've made a fair and good comment on the marurity of most off-the-shelf voip products or implementations. But the key, in my mind, is that VoIP across the internet, when done well, imports all of the opportunities of internet routing into voice service. You say that as if it's a good thing. :-) I think in the long run, it makes sense to have end-to-end IP calls over the internet. However, this is not going to be as reliable as the PSTN for many years to come, because there are is no inter-AS QoS deployment, routing protocols take their sweet time (180 seconds BGP timeout anyone?) and the internet is becoming fairly non-transparent because of all the goo people keep pouring into the machinery in the name of security and the like. However, using the public internet as a local loop is bad. Here in the Netherlands, the incumbent telco isn't allowed to lower its prices, but everyone (including the incumbent telco) can sell voice minutes to PSTN destinations over an IP local loop for any price they want. So basically they're forced to kill off the local leg of the PSTN to be able to compete on medium/long distance. This is not good. Not so long ago, when there was a failure in the long distance infrastructure, you could still make local calls. With the current intelligent networks that's not always the case anymore, but if the emergency number stuff is done properly, you can still call 911/112 when the long distance stuff is down. With inet local loop that will no longer be the case in most cities. But then, people don't really care about this, as cell is in the exact same boat and huge numbers of people rely on just their cell phone and no longer have a fixed line (in Europe at least).
Re: Replacing PSTN with VoIP wise? Was Re: Phone networks struggle in Hurricane Katrina's wake
[EMAIL PROTECTED] wrote: It's clearly possible to find telco engineers with 5/10/15 years experience in running PSTN (might even find somebody with 40-50 years? :). It's possible to find network engineers with lots of BGP experience. Where do you find a senior engineer with 5+ years experience in enterprise-scale VoIP deployment? Deployable enterprise VoIP products existed in 1998. So it would be somebody who was there doing it back then? Goes 5+ with a margin. Pete
