Re: [MMUSIC] New Version Notification for draft-reddy-mmusic-ice-happy-eyeballs-04.txt

[Ari Keränen <[e-mail]>]

On 31/01/14 15:44, Pal Martinsen (palmarti) wrote:
> On 30 Jan 2014, at 12:34 pm, Ari Keränen <[e-mail]> wrote:
>> On 28/01/14 15:49, Pal Martinsen (palmarti) wrote:
[...]
>> What I would find helpful for discussion is that if you could provide a step-by-step example of how the candidate lists are formed and connectivity checks done in cases where a) both support this with same promo algo b) both support this but with different promo algo c) only one endpoint supports this.
>>
>
> As I do believe in running code, I wrote a simple implementation of the algorithm described below.

That's very nice, but unfortunately that didn't compile on my Mac so I 
couldn't give it a try.

>> Also maybe a recommended promo algo would make sense so that there is at least a fair chance that both will use the same algo/values and get most out of this.
>>
> First shot an an algorithm:
>
> 5.  Example Algorithm for Choosing the Local Preference
>
>     The value space for the local preference is from 0 to 65535
>     inclusive.  This value space can be divided up in chunks for each IP
>     address family.
>
>     An IPv6 and IPv4 start priority must be given.  In this example IPv6
>     starts at 60000 and IPv4 at 59000.  This leaves enough address space
>     to further play with the values if pr interface priorities needs to
>     be added.  The highest value should be given to the address family
>     that should be prioritized.
>
>          IPv6    IPv4
>           Start   Start
>     65535  60k     59k    58k    57k    56k    55k                    0
>     +--------+------+------+------+------+------+---------------------+
>     |        | IPv6 | IPv4 | IPv6 | IPv4 | IPv6 |                     |
>     |        | (1)  |  (1) |  (2) |  (2) |  (3) |                     |
>     +--------+------+------+------+------+------+---------------------+
>               <- N->
>
>
>     The local preference can be calculated by the given formula:
>
>
>           local_preference = N*2*(Cn/Cmax)
>
>     Where N is the absolute value of IPv6_start-IPv4_start.  This ensures
>     a positive number even if IPv4 is the highest priority.  Cn is the
>     number of current candidates of a specific IP address type and
>     candidate type (HOST, SRFLX, RELAY).  Cmax is the number of allowed
>     consecutive candidates of the same IP address type.
>

Could you give an example how this algorithm and some priority values, 
e.g., from your program, result in the candidate pairs and order of 
checks? Especially the pairing part with respect to different types of 
candidates and IP families is where I'm afraid things may go wrong.


Cheers,
Ari