The GRE encapsulation is based on RFC 1701/2784, Generic Routing Encapsulation (GRE), WLAN-GW encapsulates according to RFC 1701 with all the flag fields set to 0, and no optional fields present. WLAN-GW can receive both encapsulations specified in RFC 1701 and RFC 2784, with all flag fields set to 0, and no optional fields present in the header.
The encapsulation is built as follows:
Outer Ethernet header: (14 bytes)
Source MAC: MAC address of the Wi-Fi AP/RG/HGW HW address
Destination MAC: MAC address of the first IP NH the Wi-Fi AP/RG/HGW is connected to (for example, CMTS, IP aggregation router, BNG, and so on)
Outer VLAN: (4 bytes): optional, typically used for service delineation in the access or aggregation network.
Outer IPv4 Header: (20 bytes)
Source IP — IP address used for WAN addressing which is retrieved by the AP/RG from the ISP through DHCP, PPPoX, and so on
Destination IP — Soft-GRE server address which can be retrieved by a DHCP Option, PPPoX option or configured by TR69 or configured statically in a boot file (in cable environment).
DSCP — Reflects QoS used in the access/aggregation network.
TTL — Should be set to 255 or should reflect the amount of IP hops in the access/aggregation network
GRE: (4 bytes)
All flags are set to 0, such as checksum, sequence number and keys are not present.
The Ether-Type is set to 0x6558 for native Ethernet is used, and 0x8847 when MPLS encapsulation is used.
MPLS Pseudowire Label (4 bytes)
Label Value, statically assigned in the Wi-Fi AP/Controller and reflected from the soft-GRE server to the Wi-Fi AP/Controller. The Label is unique within the context of the source IP address of the tunnel.
EXP: 0 (not used)
TTL: 255 (not used)
Inner Ethernet header: (14 bytes)
Source MAC: MAC address of the UE
Destination MAC: MAC address of the soft-GRE server/WLAN-GW.
Inner VLAN: (4 bytes): optional, inserted by AP/RG per unique SSID (typically, when the AP is providing SSID per retailer). WLAN-GW allows mapping the VLAN to a service context per retailer, in the data plane.
Inner IPv4 Header: (20 bytes)
Source IP: Client’s IP address obtained via DHCP (tunneled).
Destination IP: IP address of the destination client trying to reach.
DSCP: set by the client/application
TTL: set by the client/application
Soft-GRE tunnel termination is performed on dedicated IOMs with MS-ISAs (referred to as WLAN-GW IOM). Each WLAN-GW IOM requires both MS-ISAs to be plugged in for soft-GRE tunnel termination. MS-ISA provides tunnel encapsulation/decapsulation and anchor point for inter-AP mobility. The carrier IOMs of the ISA where the tunnel is terminated performs bandwidth shaping per tunnel (or per-tunnel per SSID). ESM function such as per-subscriber anti-spoofing (IP and MAC), filters, hierarchical policing, and lawful intercept are provided on the carrier IOM corresponding to the ISA where the subscriber is anchored.
An ESM and soft-gre configuration is required for wlan-gw functions. Subscriber and group interfaces are configured as part of normal ESM configuration. The group interface is enabled for wlan-gw by configuration. L2oGRE is the currently supported soft tunnel types. The wlan-gw related configuration includes the following:
Tunnel end-point IP address.
Service context for tunnel termination.
TCP MSS segment size. This is set in TCP SYN and SYN-ACKs by WLAN-GW to adjust to the MTU on access/aggregation network to prevent fragmentation of upstream and downstream TCP packets.
Mobility related configuration, including mobility trigger packet types (normal data or special Ethernet IAPP fame), and hold-down time between successive mobility triggers.
VLAN to retailer mapping. The AP typically inserts a unique dot1Q tag per retail service provider in the Ethernet payload. The mapping of dot1Q tag to retail service context is configured under wlan-gw tunnel. The subscriber is then created in the configured retail service context. The retail service context can also be provided by AAA server in authentication-accept message based on subscriber credentials or SSID information contained in DHCP Option82.
Egress QoS configuration for downstream traffic entering the wlan-gw module for tunnel encapsulation. This includes type of aggregate bandwidth shaping (per-tunnel or per-retailer), aggregate-rate-limit, egress QoS policy and scheduler policy. The tunnel shaping can be configured to be applied only when there is more than one subscriber on the tunnel. By default the shaping if configured is applied when first subscriber on the tunnel logs in.
*B:Dut-C>config>service>vprn>sub-if>grp-if>wlan-gw# info detail
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authentication
no authentication-policy
hold-time sec 5
exit
no data-triggered-ue-creation
dhcp
shutdown
active-lease-time min 10
initial-lease-time min 10
no l2-aware-ip-address
no primary-dns
no primary-nbns
no secondary-dns
no secondary-nbns
exit
egress
no agg-rate-limit
no hold-time
qos 1
no scheduler-policy
no shape-multi-client-only
no shaping
exit
gw-addresses
address 10.1.1.4
exit
no http-redirect-policy
no nat-policy
mobility
hold-time 5
no trigger
exit
router 70
no tcp-mss-adjust
track-mobility
mac-format "aa:"
no radius-proxy-cache
exit
wlan-gw-group 3
vlan-tag-ranges
range start 0 end 100
authentication
no authentication-policy
hold-time sec 5
exit
no data-triggered-ue-creation
dhcp
shutdown
active-lease-time min 10
initial-lease-time min 10
no l2-aware-ip-address
no primary-dns
no primary-nbns
no secondary-dns
no secondary-nbns
exit
no http-redirect-policy
no nat-policy
retail-svc-id 35
track-mobility
mac-format "aa:"
no radius-proxy-cache
exit
exit
exit
no shutdown