[Serusers] Deploying VoIP on a WAN

[Greger V. Teigre]

There is great pressure from large vendors of boxes to use Session Border 
Controllers.  SBCs is one of the few, new big "new product class" 
opportunitites for network equipment providers (as well as VoIP/video 
equipment providers).  The marketing machines of these giants have been 
quite successful at scaring others to design recommended interconnect etc 
using SBCs. Why is that?

IMHO, there are several reasons:
1. Traditional telcos and operators are used to "walled garden" setups and 
are mighty uncomfortable with alternative ways of handling traffic over 
their network edges
2. Sometimes it easier (and faster) to throw hardware at a problem (the 
"magic fix-it box") instead of upgrading competence and people. You contain 
a set of rather technical issues in a box and you have somebody to blame 
(the vendor)
3. The telco industry is highly reliant on the equipment and software 
vendors. Over years, there has been established a perception in the industry 
(also among executives) that unless you control and manage the full stack, 
from end-to-end, you are not taking seriously the threats to security and 
service outage ("hiding your internal topology" is a typical security 
argument that sometimes/often translates to "internal servers/boxes = no 
security", "public servers/boxes = security deliver by vendor")
4. Using SBCs you can control in more detail media streams, signalling, etc 
and some telcos and operators actually has something to gain from that. They 
want to charge for the video conference service, not allow multiple, 
concurrent and uncharged mediastreams between endpoints.

In fact, some SBCs started out as something like SER+rtpproxy + a nice web 
interface (maybe even in implementation ;-).  Then they added all sorts of 
options and control niceties.  Many SBCs' implementations have (as Jiri 
pointed out) bugs, simplistic implementations, and will most definitely over 
time constitute a large part of the cost of a roll-out for many telcos. You 
see the same problem in smaller scale with Application Layer Gateways (ALGs) 
in NATs and firewalls. Also, the firewalls look into more and more packets 
on the application layer. A simple change (or new combination of options) in 
the application layer protocol will cause problems when the ALG does not 
understand.  See the business opportunity for vendors?  (Software 
maintenance is already a large part of equipment manufacturers' revenues.)

IMO, there will be two different approaches: Some will use SBCs, some will 
not. Those who don't will increase their competence and gain experience that 
will help them every time a new service is brought the market. The SBC users 
will have trouble with "time-to-market" compared to non-SBC users. Both 
models may be successful dependent on the market they serve.

Jiri's post describes very well how SBCs in the long run can be a greater 
cost than benefit.

So, to the recommendations (yes, free ;-):
- If the endpoints are routable on the public Internet anyway (or behind a 
NAT with a public address), why do you need to hide your topology?  (that's 
one of the big problems for mobile operators as phones with Internet 
connection can get services and "only" pay for bandwidth...)
- Need for a quick, get-started, basic service with interconnect, NAT 
handling etc and have enough money: Go for SBCs (or use the SER - Getting 
Started document from ONsip.org if you don't have the money ;-)
- You're business model is based on tightly controlled services (charged per 
service/option) with high service level agreement and slow introduction of 
new services: Go for SBCs
- If you expect to introduce new services quickly, experiment with what 
sticks, want to have a flexible pricing model for bundles etc: Drop the SBCs

So, regarding interconnect: There will be providers who require SBCs (or 
recommend). Go for those without, if you don't use them yourself.  (or maybe 
more important: do your business models fit?)

g-)

----- Original Message ----- 
From: "Joao Pereira" <joao.pereira at fccn.pt>
To: "Michael Heckner" <ser at michas-zuhause.de>; "Rui Ribeiro" <racr at fccn.pt>; 
<serusers at lists.iptel.org>
Sent: Monday, February 06, 2006 9:58 PM
Subject: Re: [Serusers] Deploying VoIP on a WAN


> Michael Heckner wrote:
>
>> Hi Joao,
>>
>> Joao Pereira schrieb:
>>
>>> Hi,
>>>
>>> As many of you may know, we are undertaking several tests in order to 
>>> test
>>> the interoperability between several PBX IP from different vendors. 
>>> Until
>>> now, we were trusting that the VoIP IP PBX were good enough to be
>>> interconnected directly, however, one of the vendors have presented the 
>>> "SBC" concept.
>>>
>>> The "SBC" (Session Border Controller) is not a new concept since we were
>>> using it anyway when we setup a (Asterisk+SER+SIP Proxy) Box to handle 
>>> the
>>> "on-net dialout" calls.
>>>
>>> I'm now overwhelmed with the amount of SBCs that are suggested by the 
>>> vendors
>>> to implement a solution.
>>> (http://www.juniper.net/solutions/literature/solutionbriefs/351085.pdf)
>>>
>>> Can anyone drop me some lines about this? I urgently need some feedback 
>>> on
>>> this.
>>
>>
>> the SBC must be present whenever you leave your IP network.
>
> Ok, but can I do the same with a B2BUA in my SER/Asterisk  box?
>
>>
>> If you deal with residential users, and you work with a SIP Proxy, you 
>> want to hide your proxy and your internal topology from the outside. So 
>> you need an SBC there, or, speaking more precisly, one interface of the 
>> SBC must concentrate the external network traffic,
>>
>> The same is true, when you do interconnection with other carriers, 
>> instead of publishing the IP address of your proxy, you provide them with 
>> (another) IP address assigned to an interface of the SBC.
>
>> The amount of SBC is dependng on the expected network traffic, and the 
>> amount of interfaces, you require. Some boxes work perfectly with logical 
>> interfaces, i.e. assign multiple IP addresses to a single physical 
>> interface.
>
> Yes, thats something I can put in my SER/Asterisk box, instead of buying 
> some proprietary SBC.
>
>>
>> I propose to do detailed network and traffic engineering to ensure that 
>> you select an appropriate solution.
>
> Do you know where can I find more information about VoIP WAN deployments? 
> I want to know if the SBC is the only solution, or if it is the market 
> demanding solution. Thats because I m already calling outside my LAN, and 
> doing trunking with telcos, without the SBC....
>
>
> Joao Pereira
> FCCN
>
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