SDP Alternate Connectivity

The Oracle Communications Session Border Controller can create an egress-side SDP offer containing both IPv4 and IPv6 media addresses via a mechanism which allows multiple IP addresses, of different address families (i.e., IPv4 & IPv6) in the same SDP offer. Our implementation is based on the RFC draft "draft-boucadair-mmusic-altc-09".

Each realm on the Oracle Communications Session Border Controller can be configured with an alternate family realm on which to receive media in the alt family realm parameter in the realm config. As deployed, one realm will be IPv4, and the alternate will be IPv6. The Oracle Communications Session Border Controller creates the outbound INVITE with IPv4 and IPv6 addresses to accept the media, each in an a=altc: line and each in its own realm. The IP addresses inserted into the a=altc: line are from the egress realm’s and alt-realm-family realm’s steering pools. Observe in the image how the red lines indicate the complementary, alternate realms.

You can configure the order in which the a=altc: lines appear in the SDP in the pref-address-type parameter in the realm-config. This parameter can be set to

IPv4 - SDP contains the IPv4 address first
IPv6 - SDP contains the IPv6 address first
NONE - SDP contains the native address family of the egress realm first

In the 200OK to the INVITE, the callee chooses either the IPv6 or IPv4 address to use for the call’s media transport between itself and Oracle Communications Session Border Controller. After the Oracle Communications Session Border Controller receives the 200OK, the chosen flow is installed, and the unused socket is discarded.

For two realms from different address families to share the same phy-interface and vlan, you use a .4 or .6 tag in the network-interface reference. When IPv4 and IPv6 realms share the same network-interface and VLAN, you identify them by realm name and network-interface configured as:

IPv4 - <phy-interface>:<vlan>.4
IPv6 - <phy-interface>:<vlan>.6

If the INVITE’s egress realm is IPv6, pref-address-type = NONE, the outbound SDP has these a=altc: lines:

a=altc:1 IPv6 2001:4860:4860::8889 20001
a=altc:2 IPv4 10.10.10.21 20001

If the INVITE’s egress realm is IPv6, pref-address-type = IPv4, the outbound SDP has these a=altc: lines:

a=altc:1 IPv4 10.10.10.21 20001
a=altc:2 IPv6 2001:4860:4860::8889 20001

SDP Alternate connectivity supports B2B and hairpin call scenarios. SDP Alternate connectivity also supports singleterm, B2B, and hairpin call scenarios.

When providing SDP alternate connectivity for SRTP traffic, in the security policy configuration element, the network-interface parameter’s value must be configured with a .4 or .6 suffix to indicate IPv4 or IPv6 network, respectively.

SDP Alternate Connectivity Configuration

To configure SDP alternate connectivity:

Access the realm-config configuration element.

ORACLE# configure terminal
ORACLE(configure)# media-manager
ORACLE(media-manager)# realm-config
ORACLE(realm-config)#

Select the realm-config object to edit.

ORACLE(realm-config)# select
identifier:
1: realm01 left-left:0 0.0.0.0

selection: 1
ORACLE(realm-config)#

alt-realm-family — Enter the realm name of the alternate realm, from which to use an IP address in the other address family. If this parameter is within an IPv4 realm configuration, you will enter an IPv6 realm name.
pref-address-type — Set the order in which the a=altc: lines suggest preference. Valid values are:
- none — address family type of egress realm signaling
- ipv4 — IPv4 realm/address first
- ipv6 — IPv6 realm/address first
Type done to save your configuration.