Cisco Cisco Packet Data Gateway (PDG) Documentation Roadmaps
New In This Release
▀ Common Features
▄ Cisco ASR 5000 Series Product Overview
OL-22937-01
Benefits
This feature allows the P-CSCF to provide IPv4-IPv6 interworking in the following scenarios:
When UEs are IPv6-only and the IMS core network is IPv4-only
When UEs are IPv4-only and the IMS core network is IPv6-only
In addition, IPv4-IPv6 interworking helps an IPv4 IMS network transition to an all-IPv6 IMS network.
The following interworking requirements are currently supported:
IPv4 TCP and IPv6 TCP
Transport switching allowed based on size for both v4 and v6 network
UDP fragmentation allowed for both v4 and v6 networks
P-CSCF supports Mw and Gm interfaces on both v4 and v6
KPIs for Mw and Gm interfaces are supported on both v4 and v6
DNS supported for v4 and v6 networks
Interworking supported for IM and presence
Both v4 and v6 handsets are supported simultaneously on the same P-CSCF node
Description
P-CSCF will provide IPv4-IPv6 interworking functionality between IPv6-only UEs and IPv4-only core network
elements (I/S-CSCF) by acting as a dual stack. To achieve the dual-stack behavior, P-CSCF will be configured in two
services with the first service (V6-SVC) listening on an IPv6 address and the second service (V4-SVC) listening on an
IPv4 address. SIP messages coming from IPv6 UEs will come to V6-SVC and will be forwarded to the IPv4 core
network through V4-SVC. Similarly, messages from the IPv4 core network come to V4-SVC and will be forwarded to
IPv6 UEs via V6-SVC. P-CSCF also provides interworking functionality between IPV4-only UEs and IPv6-only core
network elements.
elements (I/S-CSCF) by acting as a dual stack. To achieve the dual-stack behavior, P-CSCF will be configured in two
services with the first service (V6-SVC) listening on an IPv6 address and the second service (V4-SVC) listening on an
IPv4 address. SIP messages coming from IPv6 UEs will come to V6-SVC and will be forwarded to the IPv4 core
network through V4-SVC. Similarly, messages from the IPv4 core network come to V4-SVC and will be forwarded to
IPv6 UEs via V6-SVC. P-CSCF also provides interworking functionality between IPV4-only UEs and IPv6-only core
network elements.
To identify the need for v4-v6 interworking for a new incoming IPv6 REGISTER arriving at V6-SVC, a route lookup is
performed based on the request-uri, first in V4-SVC context and then in V6-SVC context if the first lookup does not
return any matching route entry. If a matching IPv4 next-hop route entry is found, then this indicates that interworking
needs to be done. If no route entry is found, then a DNS query on request-uri domain is done for both A and AAAA
type records. If DNS response yields only an IPv4 address, then this is also the case for performing v4-v6 interworking.
performed based on the request-uri, first in V4-SVC context and then in V6-SVC context if the first lookup does not
return any matching route entry. If a matching IPv4 next-hop route entry is found, then this indicates that interworking
needs to be done. If no route entry is found, then a DNS query on request-uri domain is done for both A and AAAA
type records. If DNS response yields only an IPv4 address, then this is also the case for performing v4-v6 interworking.
Headers (such as Via, Path, etc.) are automatically set to IPv4 bind address of P-CSCF V4-SVC. Remaining headers
will be not be altered and sent as is toward the S-CSCF. The IPv4 address in a Path header received from S-CSCF in
200Ok of REGISTER will be replaced with V6-SVC‘s IPv6 address before forwarding to UE.
will be not be altered and sent as is toward the S-CSCF. The IPv4 address in a Path header received from S-CSCF in
200Ok of REGISTER will be replaced with V6-SVC‘s IPv6 address before forwarding to UE.
P-CSCF handling different v4-v6 interworking scenarios is shown below.
Figure 6.
v4v6interworking.wmf