Cisco ASR 5000 Series, Обзор продукта

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ASN Gateway Overview
▀ Data Tunnel Endpoint Support
▄ Cisco ASR 5000 Series Product Overview
OL-22938-02
Data Tunnel Endpoint Support
ASNGW supports forwarding downlink data to different endpoint tunnels other than the control address on the BS. In
addition, the ASNGW can process uplink data and control traffic on different paths (VLANs) on the ASNGW if the data
and control traffic are hosted on a different IP address.
The control and data tunnel endpoint can be different for the BS or the ASNGW. If the data tunnel endpoint is different
from the control endpoint, it applies for both downlink and uplink traffic destined to, or received from, the peer (BS or
ASNGW). This means that when downlink traffic is sent to the peer, the data tunnel endpoint is the destination IP
address; when the uplink traffic is received from this peer, the source IP address is the data tunnel endpoint. The GRE
key is unique for downlink and uplink data paths.
ASNGW with a Different Tunnel Endpoint
The ASNGW supports different data tunnel points on the BS for downlink traffic. The BS conveys its data tunnel
endpoint through the existing R6 TLVs within MS Info.
If the uplink has a different data tunnel point, the ASNGW adds this information in the message that carries MS
information, including the TLV or data path TLV that describes uplink service flow. There is a unique GRE key
assigned to the uplink data path.
The ASNGW includes the tunnel endpoint TLV in the data path messages to BS or from the non-anchor GW to the
anchor GW and vice-versa, to support the handoff functionality. After receiving the tunnel endpoint TLV within the
data path messages, the BS forwards all the uplink data traffic to the same address.
No Handoff (INE)
For the control and data path setup for the INE, the BS/ASN specifies the different IP addresses for control and data
traffic. For example, DT1 and BS1 are the data and control endpoints on the BS side. AS1 and AT1 are the data and
control endpoints respectively on the ASNGW side. If the ASNGW requires different data tunnel endpoints instead of
control addresses, the tunnel endpoint IP address has to be populated in the MS information TLV if it is per BS for DP
Reg Request/Response message.
The ASNGW creates an NPU flow using the tunnel IP address if received in the DP Reg Response message for the
uplink packet. From now on, all the data packets received from the BS have the source address of DT1. For all the
downlink traffic, the ASNGW forms the data packet using the ASNGW Data IP address as the source address; the AT1
and destination address of the tunnel are the tunnel endpoint (that is, DT1). If no tunnel end point attribute is received
from BS/ASNGW, by default, the control IP address is used for data traffic.
If the ASNGW requires a different data tunnel endpoint instead of a control address, the tunnel endpoint IP address is
populated in the MS information TLV if it is per BS for DP Reg Request/Response message.