PDN Gateway Overview
Features and Functionality - Base Software ▀
Cisco ASR 5x00 Packet Data Network Gateway Administration Guide ▄
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If the UE requests IPv4 Link MTU size in the PCO options during Initial Attach or PDN connectivity request, the P-GW
will provide the preconfigured value based on the APN.
If the MTU size configuration on APN is changed, the new MTU size will take effect only for new PDN connections
and initial attaches. P-GW will not update for the existing PDN connections.
If UE does not request IPv4 Link MTU size, P-GW will not include the IPv4 Link MTU size.
Multiple PDN Support
Enables an APN-based user experience that enables separate connections to be allocated for different services including
IMS, Internet, walled garden services, or off-deck content services.
The MAG function on the S-GW can maintain multiple PDN or APN connections for the same user session. The MAG
runs a single node level Proxy Mobile IPv6 tunnel for all user sessions toward the LMA function of the P-GW. When a
user wants to establish multiple PDN connections, the MAG brings up the multiple PDN connections over the same
PMIPv6 session to one or more P-GW LMAs. The P-GW in turn allocates separate IP addresses (Home Network
Prefixes) for each PDN connection and each one can run one or multiple EPC default & dedicated bearers. To request
the various PDN connections, the MAG includes a common MN-ID and separate Home Network Prefixes, APNs and a
Handover Indication Value equal to one in the PMIPv6 Binding Updates.
Important:
Up to 11 multiple PDN connections are supported.
Node Functionality GTP Echo
This feature helps exchange capabilities of two communicating GTP nodes, and uses the new feature based on whether
it is supported by the other node.
This feature allows S-GW to exchange its capabilities (MABR, PRN, NTSR) with the peer entities through ECHO
messages. By this, if both the peer nodes support some common features, then they can make use of new messages to
communicate with each other.
With new “node features” IE support in ECHO request/response message, each node can send its supported features
(MABR, PRN, NTSR). This way, S-GW can learn the peer node’s supported features. S-GW’s supported features can
be configured by having some configuration at the service level.
If S-GW wants to use new message, such as P-GW Restart Notification, then S-GW should check if the peer node
supports this new feature or not. If the peer does not support it, then S-GW should fall back to old behavior.
If S-GW receives a new message from the peer node, and if S-GW does not support this new message, then S-GW
should ignore it. If S-GW supports the particular feature, then it should handle the new message as per the specification.
Non-Optimized e-HRPD to Native LTE (E-UTRAN) Mobility Handover
This feature enables a seamless inter-technology roaming capability in support of dual mode e-HRPD/e-UTRAN access
terminals.
The non-optimized inter-technology mobility procedure is rooted at the P-GW as the mobility anchor point for
supporting handovers for dual radio technology e-HRPD/E-UTRAN access terminals. To support this type of call
handover, the P-GW supports handoffs between the GTP-based S5/S8 (GTPv2-C / GTPv1-U) and PMIPv6 S2a
tunneled connections. It also provisions IPv4, IPv6, or dual stack IPv4/IPv6 PDN connections from a common address
