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iWAG-GTP: S2a
Interface Support and High Availability Enhancements
This chapter
describes the enhancements for Intelligent Wireless Access Gateway-General
Packet Radio Service Tunneling Protocol (iWAG-GTP) to support S2a interface
type and related features for the trusted Wireless LAN (WLAN) Access Network
deployment.
This chapter also
covers iWAG-GTP high availability and In-Service Software Upgrade (ISSU)
enhancements to support different GTP-C and GTP-U addresses from Cisco Packet
Data Network Gateway (PGW) and Gateway GPRS Support Node (GGSN).
This chapter contains the following topics:
Finding Feature
Information
Your software release may not support all the features documented in
this module. For the latest caveats and feature information, see
Bug Search Tool and the
release notes for your platform and software release. To find information about
the features documented in this module, and to see a list of the releases in
which each feature is supported, see the feature information table at the end
of this module.
Use Cisco Feature Navigator to find information about platform support
and Cisco software image support. To access Cisco Feature Navigator, go to
www.cisco.com/go/cfn. An account on
Cisco.com is not required.
Information About
S2a Interface Support for GTPv2
iWAG-GTP supports the
S2a interface for trusted networks. Earlier, the implementation of GPRS
Tunneling Protocol Version 2 (GTPv2) on iWAG-GTP supported only the S5
interface and S8 interface that connect a serving gateway (SGW) and a packet
data network gateway (PGW). Effective from Cisco IOS XE Release 3.14, by
default, GTPv2 supports the S2a interface on the iWAG side for trusted WLAN
Access Network deployment, according to the specifications provided in 3GPP TS
29.274 V11.5.0.
In the new S2a
interface, GTPv2 supports some new information elements like Additional
Protocol Configuration Options (APCO) for Domain Name System (DNS)
provisioning, and IPv4 Configuration Parameters (IP4CP) for dynamic default
gateway provisioning.
The interface that
connects the iWAG to PGW is configurable for backwards compatibility, and S2a
interface is used by default.
ISSU and High
Availability Support for GTPv2
Because GTPv2
supports both S5/S8 interface and S2a interface, the interface type should be
stored on a per-PDP basis, so that the same interface type is used when
deleting the PDP.
In a high
availability (HA) scenario, the interface type should be checkpointed to the
standby RP so that after switchover, a PDP on the newly active RP has the
interface type information.
Table 1. ISSU and High
Availability Support for GTPv2
S5/S8
S2a
ISSU Upgrade
Supported
ISSU upgrade
is not applicable for S2a interface.
In releases
prior to Cisco IOS XE 3.14, S2a interface type was not supported.
ISSU Downgrade
Supported
Not
supported.
After
downgrade, only the S5/S8 interface type is supported, it may not be possible
to delete sessions.
SSO
Checkpoint
Supported
Supported
from Cisco IOS XE Release 3.14 onwards.
Example:
Configuring the S2a Interface for GTPv2
The following
example shows how to configure the S2a interface for GTPv2:
Router(config)#gtp
Router(config-gtp)#apn 1
Router(config-gtp-apn)#gtpv2 interface-type ?
s2a Interface between TWAG and PGW (default value for backwards compatibility)
s5s8 Interface between SGW and PGW
GTP Control and GTP
User Tunnel Address Separation for GTPv1 and GTPv2
In Cisco IOS XE
Release 3.11 and earlier, iWAG-GTP did not support separate GTP-C and GTP-U
paths to GGSN and PGW.
Effective from Cisco
IOS XE Release 3.12, iWAG-GTP partially supports GTP-C and GTP-U address
separation. The separation works only on non-high availability boxes because
there is no checkpointing of the GGSN and PGW data path (GTP-C) address to
standby RPs.
Effective from Cisco
IOS XE Release 3.14, iWAG-GTP supports different GTP-C and GTP-U addresses in
an HA setup for both GTPv1 and GTPv2.
Note
GTP path version is
not checkpointed to standby RPs. Therefore, GTPv1 and GTPv2 sessions are not
supported on the same path.
Additional PCO
Support on S2a Interface for DNS Provisioning
Effective from Cisco
IOS XE Release 3.14, GTPv2 supports a new information element type called
additional PCO to support DNS provisioning over the S2a interface.
Additional PCO
applies only to transparent single-connection mode. You can use PCO or
additional PCO options for DNS provisioning, but the default option is
additional PCO.
Example: Configuring
Additional PCO for GTPv2
The following
example shows how to configure additional PCO for GTPv2:
Router(config)#gtp
Router(config-gtp)#apn 1
Router(config-gtp-apn)#gtpv2 pco-type ?
apco Using APCO for DNS provisioning (default value for backwards compatibility)
pco Using PCO for DNS provisioning
IP4CP Support on
S2a Interface for Dynamic Provisioning of Default Gateway
The S2a interface
supports IPv4 Configuration Parameters (IP4CP) information element type. IP4CP
information element enables the PGW to dynamically provision the default
gateways instead of tedious local configuration on the iWAG. IP4CP is
applicable only to transparent single-connection mode.
In order to be
backward compatible, local configuration of default gateways is supported.
If the default
gateway address and subnet prefix length provisioned from PGW are the same as
for the locally configured default gateway, the default gateway is created as a
static default gateway.
If local
configuration does not exist, the dynamically provisioned default gateway is
used.
If there is no
IP4CP to provision the dynamic default gateway and there is no local
configuration, session creation fails due to the absence of a default gateway.
APN-AMBR Support for
GTPv2
APN aggregate maximum
bit rate (AMBR) is the maximum allowed total nonguaranteed bit rate (GBR)
throughput to a specific APN. It is specified interdependently for uplink and
downlink. The APN-AMBR IE type is used to define the per-APN uplink and
downlink aggregate maximum bit rate for a specific UE.
Effective from Cisco
IOS XE Release 3.14, GTPv2 supports the APN-AMBR IE type for uplink and
downlink.
Example:
Configuring APN-AMBR Uplink and Downlink for GTPv2
The following
example shows how to configure APN-AMBR uplink and downlink for GTPv2:
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Feature Information
for iWAG-GTP: S2a Interface Support and High-Availability Enhancements
The following table provides release information about the feature or features described in this module. This table lists
only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise,
subsequent releases of that software release train also support that feature.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco
Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.
Table 2. Feature Information for
iWAG-GTP: S2a Interface Support and High-Availability Enhancements
Feature
Name
Releases
Feature
Information
iWAG-GTP:
S2a Interface Support and High-Availability Enhancements
Cisco IOS
XE Release 3.14
In Cisco IOS
XE Release 3.14, this feature was implemented on the Cisco ASR 1000 Series
Aggregation Services Routers.