AudioCodes Mediant 4000 SBC User Manual page 464

CHAPTER 19 Coders and Profiles
Parameter Description
■ [3] Prefer IPv6 = SDP offer includes IPv4 and IPv6
media IP addresses, but the first (preferred) media is
IPv6.
To indicate ANAT support, the device uses the SIP Allow
header or to enforce ANAT it uses the Require header:
Require: sdp-anat
In the outgoing SDP, each 'm=' field is associated with an
ANAT group. This is done using the 'a=mid:' and
'a=group:ANAT' fields. Each 'm=' field appears under a
unique 'a=mid:' number, for example:
a=mid:1
m=audio 63288 RTP/AVP 0 8 18 101
c=IN IP6 3000::290:8fff:fe40:3e21
The 'a=group:ANAT' field shows the 'm=' fields belonging
to it, using the number of the 'a=mid:' field. In addition, the
ANAT group with the preferred 'm=' fields appears first. For
example, the preferred group includes 'm=' fields under
'a=mid:1' and 'a=mid3':
a=group:ANAT 1 3
a=group:ANAT 2 4
If you configure the parameter to a "prefer" option, the
outgoing SDP offer contains two medias which are the
same except for the "c=" field. The first media is the
preferred address type (and this type is also on the session
level "c=" field), while the second media has its "c=" field
with the other address type. Both medias are grouped by
ANAT. For example, if the incoming SDP contains two
medias, one secured and the other non-secured, the device
sends the outgoing SDP with four medias:
■ Two secured medias grouped in the first ANAT group,
one with IPv4 and the other with IPv6. The first is the
preferred type.
■ Two non-secured medias grouped in the second ANAT
group, one with IPv4 and the other with IPv6. The first
is the preferred type.
Note:
■ The parameter is applicable only when the device offers
an SDP.
■ The IP addressing version is determined according to
the first SDP "m=" field.
■ The feature is applicable to any type of media (e.g.,
audio and video) that has an IP address.
■ The corresponding global parameter is
MediaIPVersionPreference.
- 431 -
Mediant 4000 SBC | User's Manual