Re: [Softwires] GI-DS-lite as working group item?

[Behcet Sarikaya <[e-mail]>]

Hi Med,



> Dear Cameron, all,

GI-DSLite does not define any protocol but an 
> architecture where a tunnel is used together with a new enhanced NAT44 table 
> (because more de-multiplexing information than for basic NAT44 table is 
> required). So, what should be standardised there?

(1) The behaviour of 
> the gateway?

(2) The tunnel establishment "procedure"? This is an 
> operational consideration as a matter of fact. In addition, the tunnel is not 
> required in the majority of the scenarios. Normal routing actions can be done in 
> the gateway to redirect the traffic to the appropriate CGN. I don't see a 
> deployment context where more that +16M UEs (or Access Devices) will be serviced 
> by the same CGN device. 

(3) The structure of the enhanced NAT table?: 
> Other proposals are on the table such as Layer-2 Aware NAT 
> (http://tools.ietf.org/html/draft-miles-behave-l2nat-00) or Per-interface NAT 
> (http://tools.ietf.org/html/draft-arkko-dual-stack-extra-lite-00). Should we 
> define a generic table structure for all enhanced NAT? 

The document does 
> not define the problem to be solved and neither why a new solution is required. 
> Is the targeted problem a valid problem to be solved? Please find below my 
> analysis on the mobile use case. Several scenarios can be envisaged as listed 
> below:

> (a) Co-located model: the NAT is co-located in the PGW/GGSN. No 
> issue with private IPv4 addresses. GTP TID can even be used a de-multiplexing 
> factor if required.

> (b) 1:1 model: the CGN and the PGW/GGSN are not 
> embedded in the same device. Each PGW/GGSN is configured how to reach its 
> attached CGN. There is no private IPv4 @ depletion problem.

> (c) N:1 
> model: a single CGN serve a group of PGW/GGSN. Indeed, having +16M of customers 
> is a valid case. **BUT** which Service Provider will accept to service this huge 
> amount of UEs with the same node (if we suppose that a mega centralised CGN 
> implementation is found in the market)? This is single point of failure design 
> which SHOULD NOT BE RECOMMENDED.

IMHO it is N:1 and that's why GI-DS lite is interesting to the operators. I agree with you that having 16M+ MNs NAT'ed by a single CGN is something I have not heard of, yes there there is a problem.

Let's hope that we are not going to have that problem. If IPv6 migration progresses fast we may not.


Regards,

Behcet