Data-Plane; Uplink Data Path; Downlink Data Path; Overlapping Ip Address Support - Cisco ASR 5000 Administration Manual

▀ Product Overview

Data-Plane

Uplink Data Path

The uplink data packet from UE is sent by WLC to D-eWAG over the mapped VLAN for that UE session. D-eWAG
identifies the session for the received data-packet based on the source IP address. After the session is identified, the data
packet is placed over the GTP-U tunnel created with GGSN for this session. This ensures that the packet reaches the
appropriate APN network.

Downlink Data Path

D-eWAG uniquely identifies a session based on the GTP-U tunnel from GGSN and extracts the IP packet from GTP-U
tunnel. This IP packet contains the destination IP address set to the UE's IP address allocated during DHCP signaling
(and actually allocated by GGSN). D-eWAG sends the IP packet downstream to the WLC over the correct VLAN. D-
eWAG always uses the same VLAN over which the DHCP packets are received for this UE session in this case. The
WLC also takes care of delivering the IP packet to the UE over WLAN.

Overlapping IP Address Support

Important:
available only for lab testing purposes.
If the IP address allocated by GGSN during the PDP Context Creation is expected to be unique for each UE session
(across the different APN/PLMN), then Overlapping IP Address support is not required. In that case, identification of
the session for the data-traffic at D-eWAG can be based only on the Source IP address.
To support Overlapping IP addresses, identification of data-traffic is done based on the {VLAN-ID, Source-IP-Address}
pair, which ensures that the overlapping IP addresses can exist across operators/APN.
Following table shows the overlapping IP address support in various possible deployment models of D-eWAG:
Table 5. Overlapping IP Address Support
Model
One SSID mapped to one
VLAN mapped to one
APN.
One SSID mapped to one
VLAN mapped to multiple
APN.
One SSID mapped to
multiple VLAN mapped to
one APN.
▄ Cisco ASR 5000 Enhanced Wireless Access Gateway Administration Guide
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In this release, Overlapping IP Address support is not fully qualified and is not supported, it is
Overlapping IP Support
Yes, the VLAN has to be
always different for different
APN.
No
Yes, the VLAN has to be
always different for different
APN.
DHCP-based Enhanced Wireless Access Gateway Overview
Notes
a. Each SSID should always be mapped to unique VLAN in this
case even if it is served using multiple WLCs.
b. Different VLAN used for all UE sessions connecting through
different SSIDs and uplink packets can be identified uniquely with
{vlan+src.ip} pair at D-eWAG.
a. Each SSID should always be mapped to a unique VLAN in this
case, even if it is served using multiple WLCs.
b. Same VLAN used for all UE sessions and uplink packets cannot
be identified uniquely with {vlan+src.ip} pair at D-eWAG.
a. WLCs can be different with different VLAN for same SSID.
b. WLC can be configured with AP-Group to use different VLAN.
c. Set of VLANs serving one APN are different from set of VLANs
serving another APN. This way overlapping-ip can be supported.