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This is super interesting. In full blown 4g networks, voice is going to be handled via sip traffic via an IMS core. Some things to investigate: Is Verizon us

This is super interesting. In full blown 4g networks, voice is going to be handled via sip traffic via an IMS core. Some things to investigate: Is Verizon using separate APNs for their voice and data. Based on what is presented, I am guessing no... And that they jhave routing/QoS rules that are rather ungranular. They assume all sip traffic must be their own IMS traffic and then route it to their ims core, where a proxy is damaging the flow. Anyone who thinks that an operator will allow you to use SIP traffic over their LTE network forever is incomprehensibly naive. Paying customer voice traffic should not have to compete for resources with your data traffic. Net neutrality is not a suicide pact.

mdasen 13y ago
With Verizon, there's an issue of open access. Verizon bid on 700MHz spectrum with special "open access" rules that require them to allow any application. In the 2008 700MHz auction, there were five blocks up for auction and Verizon went for the one band that had these restrictions: that customers be allowed to use any compatible device they like and use any software, content, or services they like. Paying customer voice traffic is today, and can be in the future, carried on other spectrum.
- droopybuns 13y ago
  Spectrum is only part of the equation... And if they didn't design things right, they won't be able to take advantage of spectrum differently like you propose.
  - mdasen 13y ago
    Yeah. . .but to be a bit crass, that's totally Verizon's problem. I mean, at some point they have to have had meetings, "so, how will these open access rules affect our future?" And yea, I'm being a bit silly when I say "they have to have" (this is going to be a bit of a silly comment). Companies do dumb things all the time. But if the response was, "eh, who cares. I'm sure people will forget about it," then it's kinda their own fault. Without these restrictions, that spectrum may have raised more money. It was auctioned with these restrictions with the idea that the restrictions are in the public interest and that it might cause the winner to undergo additional costs or lose certain pricing options. If the result is, "c'mon dude, you can't really expect us to do that," I don't have a lot of pity for it. Net neutrality isn't meant to be a suicide pact, but to be frank, almost all of the wireless spectrum that the FCC has made available for mobile doesn't carry this restriction. Verizon knew this restriction going in and could have chosen not to bid on that spectrum. I think with Verizon having gone in with full knowledge of the restrictions involved, it's reasonable to hold them accountable.
p1mrx 13y ago
The big question is, does this only affect IPv4? Last time I had a Verizon phone, the IMS interface was IPv6-only, so VoLTE will probably use IPv6 as well.
- snuxoll 13y ago
  Yeah, it's because VZW uses carrier grade NAT for IPv4 traffic, when using IPv6 you get a publicly addressable IP and it's a non-issue.
Zigurd 13y ago
Nobody is running VoLTE, and there are no VoLTE handsets in the wild, and if they were running VoLTE, there is no way that SIP traffic could harm it any more than any other kind of traffic. Nor is SIP used solely for voice calls. C'mon, a "suicide pact?" That's way over the top. So to speak.
kevin_nisbet 13y ago
IMS/QOS on LTE is actually a very complicated topic, as it goes beyond routing/QoS rules. I'll try and comment on some of the points you hit on. So to clear up a few things: 1. They assume all sip traffic must by their own, and route to their IMS Core IMS SIP proxy information is relayed to the device when it attached to the network if it's IMS capable. It's up to the devices stack to use the proxy provided by the network, which as far as I'm aware no 3rd party software does at the moment. 2. Is Verizon using separate APNs for their voice and data. Based on http://support.verizonwireless.com/clc/devices/knowledge_base.html?id=46578 http://support.verizonwireless.com/clc/devices/knowledge_bas... it appears they may use vzwims I believe by convention, for roaming the "ims" APN is to be used, however, I'm having trouble locating the recommendation by either the GSMA or 3GPP, so now i'm not sure where I heard that. 3. routing/QoS rules that are rather nongranular Actually, LTE has spent immense effort in providing capabilities and controls around prioritizing very specific traffic. In high level concept, when you use the IMS core to generate a SIP call, the local SIP proxies will have links back to the PCRF (policy server). The PCRF is capable of generating IP Source/Destination rules that are sent to the network, to prioritize the specific RTP conversation. This is taken to the level in LTE network's, where the LTE network depending on the rule will "Guarantee" the bitrate is available, and the rule is pushed to all aspects of the network include the eNodeB (Cell Site). The over the air scheduler in the eNodeB is to respect the QoS rules to ensure traffic such as conversational-voice does not receive jitter/packet loss from background traffic (such as file transfer). Obviously, if you don't use the IMS core, you lose this capability, since it's not based on packet inspection, but by the proxy server itself knowing a call is in progress, and creating dynamic QoS rules just for that call. Even with the way net neutrality is going, from my view it looks like the standards body is providing the capabilities for a fairly QoS rich environment. Personally I don't have a problem with, the network understanding that your doing web browsing, and to deliver a better experience, you get higher network priority for you're basic web viewing, then the person down the street who's doing background file transfer, and saturating the cell site. The net neutrality problem is, if the carrier tries to leverage this not for experience, but profiteering, or to block certain types of traffic. However, that's a much larger debate that I don't think belongs here. 4. Paying customer voice traffic should not have to compete for resources with your data traffic This is effectively true already (see number 3 above). However, your point is more around that this is reason to block non-carrier SIP, which isn't the case. As an operator, I can just lop it in with the rest of the background data traffic, and you receive a user experience that matches. Since this is background data, there is also less of a guarantee that the service will work consistently, as it's not something explicitly tested for or verified in the many pieces of network infrastructure. As is indicated in other posts, this sounds like issues with the ALG, however, there are all kinds of things that can go wrong, NAT, Firewall, IDS. I once worked a problem with RTCP/RTP a number of years ago, where a bug in one of the network elements, actually got confused by the STUN packet, because it was being too smart and setting up rules based on inspection of RTCP. The funny thing about it, was that everything would've worked fine, if it wasn't being too clever to try and solve the problem for us. *I do work in the telecom industry, however, my views and comments do not reflect my employer in any way. All information here can be found publicly when knowing where to look, or is my own opinion.
yaantc 13y ago
VoLTE is not deployed yet (but soon). Voice and in general IMS traffic will use a separate APN, per the GSMA VoLTE specification. This spec requires that an APN called "IMS" be used, and Verizon is complying (even today, SMS is done over IMS with LTE). All operators will do that.

mdasen 13y ago

With Verizon, there's an issue of open access. Verizon bid on 700MHz spectrum with special "open access" rules that require them to allow any application. In the 2008 700MHz auction, there were five blocks up for auction and Verizon went for the one band that had these restrictions: that customers be allowed to use any compatible device they like and use any software, content, or services they like. Paying customer voice traffic is today, and can be in the future, carried on other spectrum.

droopybuns 13y ago
Spectrum is only part of the equation... And if they didn't design things right, they won't be able to take advantage of spectrum differently like you propose.
- mdasen 13y ago
  Yeah. . .but to be a bit crass, that's totally Verizon's problem. I mean, at some point they have to have had meetings, "so, how will these open access rules affect our future?" And yea, I'm being a bit silly when I say "they have to have" (this is going to be a bit of a silly comment). Companies do dumb things all the time. But if the response was, "eh, who cares. I'm sure people will forget about it," then it's kinda their own fault. Without these restrictions, that spectrum may have raised more money. It was auctioned with these restrictions with the idea that the restrictions are in the public interest and that it might cause the winner to undergo additional costs or lose certain pricing options. If the result is, "c'mon dude, you can't really expect us to do that," I don't have a lot of pity for it. Net neutrality isn't meant to be a suicide pact, but to be frank, almost all of the wireless spectrum that the FCC has made available for mobile doesn't carry this restriction. Verizon knew this restriction going in and could have chosen not to bid on that spectrum. I think with Verizon having gone in with full knowledge of the restrictions involved, it's reasonable to hold them accountable.

p1mrx 13y ago

The big question is, does this only affect IPv4? Last time I had a Verizon phone, the IMS interface was IPv6-only, so VoLTE will probably use IPv6 as well.

snuxoll 13y ago
Yeah, it's because VZW uses carrier grade NAT for IPv4 traffic, when using IPv6 you get a publicly addressable IP and it's a non-issue.

Zigurd 13y ago

Nobody is running VoLTE, and there are no VoLTE handsets in the wild, and if they were running VoLTE, there is no way that SIP traffic could harm it any more than any other kind of traffic. Nor is SIP used solely for voice calls. C'mon, a "suicide pact?" That's way over the top. So to speak.

kevin_nisbet 13y ago

IMS/QOS on LTE is actually a very complicated topic, as it goes beyond routing/QoS rules. I'll try and comment on some of the points you hit on. So to clear up a few things: 1. They assume all sip traffic must by their own, and route to their IMS Core IMS SIP proxy information is relayed to the device when it attached to the network if it's IMS capable. It's up to the devices stack to use the proxy provided by the network, which as far as I'm aware no 3rd party software does at the moment. 2. Is Verizon using separate APNs for their voice and data. Based on http://support.verizonwireless.com/clc/devices/knowledge_base.html?id=46578 http://support.verizonwireless.com/clc/devices/knowledge_bas... it appears they may use vzwims I believe by convention, for roaming the "ims" APN is to be used, however, I'm having trouble locating the recommendation by either the GSMA or 3GPP, so now i'm not sure where I heard that. 3. routing/QoS rules that are rather nongranular Actually, LTE has spent immense effort in providing capabilities and controls around prioritizing very specific traffic. In high level concept, when you use the IMS core to generate a SIP call, the local SIP proxies will have links back to the PCRF (policy server). The PCRF is capable of generating IP Source/Destination rules that are sent to the network, to prioritize the specific RTP conversation. This is taken to the level in LTE network's, where the LTE network depending on the rule will "Guarantee" the bitrate is available, and the rule is pushed to all aspects of the network include the eNodeB (Cell Site). The over the air scheduler in the eNodeB is to respect the QoS rules to ensure traffic such as conversational-voice does not receive jitter/packet loss from background traffic (such as file transfer). Obviously, if you don't use the IMS core, you lose this capability, since it's not based on packet inspection, but by the proxy server itself knowing a call is in progress, and creating dynamic QoS rules just for that call. Even with the way net neutrality is going, from my view it looks like the standards body is providing the capabilities for a fairly QoS rich environment. Personally I don't have a problem with, the network understanding that your doing web browsing, and to deliver a better experience, you get higher network priority for you're basic web viewing, then the person down the street who's doing background file transfer, and saturating the cell site. The net neutrality problem is, if the carrier tries to leverage this not for experience, but profiteering, or to block certain types of traffic. However, that's a much larger debate that I don't think belongs here. 4. Paying customer voice traffic should not have to compete for resources with your data traffic This is effectively true already (see number 3 above). However, your point is more around that this is reason to block non-carrier SIP, which isn't the case. As an operator, I can just lop it in with the rest of the background data traffic, and you receive a user experience that matches. Since this is background data, there is also less of a guarantee that the service will work consistently, as it's not something explicitly tested for or verified in the many pieces of network infrastructure. As is indicated in other posts, this sounds like issues with the ALG, however, there are all kinds of things that can go wrong, NAT, Firewall, IDS. I once worked a problem with RTCP/RTP a number of years ago, where a bug in one of the network elements, actually got confused by the STUN packet, because it was being too smart and setting up rules based on inspection of RTCP. The funny thing about it, was that everything would've worked fine, if it wasn't being too clever to try and solve the problem for us. *I do work in the telecom industry, however, my views and comments do not reflect my employer in any way. All information here can be found publicly when knowing where to look, or is my own opinion.

yaantc 13y ago

VoLTE is not deployed yet (but soon). Voice and in general IMS traffic will use a separate APN, per the GSMA VoLTE specification. This spec requires that an APN called "IMS" be used, and Verizon is complying (even today, SMS is done over IMS with LTE). All operators will do that.