Дорожная карта для Cisco Cisco Packet Data Gateway (PDG)
PDG/TTG Overview
Network Deployment(s) and Interfaces ▀
Cisco ASR 5000 Series Product Overview ▄
OL-22938-01
GTP (GPRS Tunneling Protocol) is the primary protocol used in the GPRS core network. It allows subscribers in a
UMTS network to move from place to place while continuing to connect to the Internet as if from one location at the
GGSN. It does this by carrying the subscriber‘s data from the subscriber‘s current SGSN to the GGSN that is handling
the subscriber‘s session.
UMTS network to move from place to place while continuing to connect to the Internet as if from one location at the
GGSN. It does this by carrying the subscriber‘s data from the subscriber‘s current SGSN to the GGSN that is handling
the subscriber‘s session.
The TTG functions as an SGSN in the GPRS/UMTS network to provide an SGTP (SGSN GPRS Tunneling Protocol)
service. The SGTP service enables the TTG to use GTP over the Gn' interface to carry packet data between itself and
the GGSN.
service. The SGTP service enables the TTG to use GTP over the Gn' interface to carry packet data between itself and
the GGSN.
TTG Logical Network Interfaces (Reference Points)
The following table provides descriptions of the logical network interfaces supported by the TTG in a GPRS/UMTS
data network.
data network.
Table 68. TTG Logical Network Interfaces
Interface
Description
Wu
The reference point between the WLAN UE and the TTG.
The Wu interface carries the IPSec tunnels between the UEs in the WLAN and the TTG. The IPSec tunnels carry the
ESP (Encapsulating Security Payload) packets between the UEs and the TTG.
The Wu interface carries the IPSec tunnels between the UEs in the WLAN and the TTG. The IPSec tunnels carry the
ESP (Encapsulating Security Payload) packets between the UEs and the TTG.
Wm
The reference point between the TTG and the 3GPP AAA server.
Gn'
The reference point between the TTG and the GGSN.
To provide PDG functionality in existing GGSN deployments, the TTG functions as an SGSN. For every IPSec tunnel
that is established between the TTG and a WLAN UE, the TTG initiates a PDP context and a corresponding GTP
tunnel over the Gn' interface to the GGSN. The TTG forwards the W-APN and IMSI of the WLAN UE to the GGSN in
the Create-PDP-Context-Request message.
The following messages are supported over the Gn' reference point:
To provide PDG functionality in existing GGSN deployments, the TTG functions as an SGSN. For every IPSec tunnel
that is established between the TTG and a WLAN UE, the TTG initiates a PDP context and a corresponding GTP
tunnel over the Gn' interface to the GGSN. The TTG forwards the W-APN and IMSI of the WLAN UE to the GGSN in
the Create-PDP-Context-Request message.
The following messages are supported over the Gn' reference point:
Create PDP Context Request / Response
Update PDP Context Request / Response
Delete PDP Context Request / Response
Error Indication
Version Not Supported
GTP Payload Forwarding
GTP Echo