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jpereira edited this page Oct 17, 2014 · 14 revisions

SoftGREd

The Linux OpenSource solution for L2oGRE inspired on Alcatel 7750, used to Auto Provisioning for Tunnel GRE (Generic Routing Encapsulation)

Welcome to the SoftGREd wiki! Here you can find all relevant information to the SoftGREd service. It is tried to keep the information as current as possible. Feel free to add/change/correct if you see something missing or wrong.

What is L2oGRE Tunnels?

Soft-GRE refers to stateless GRE tunneling, whereby the AP forwards GRE encapsulated traffic to the WLAN-GW, and the GW reflects back the encapsulation in the downstream traffic towards the AP. WLAN-GW does not require any per-AP end-point IP address configuration. The WLAN-GW learns the encapsulation as part of creating the subscriber state on processing the encapsulated control and data traffic.

Encapsulation

The GRE encapsulation is based on RFC 1701/2784, Generic Routing Encapsulation (GRE), WLAN-GW will encapsulate according to RFC 1701 with all the flag fields set to 0, and no optional fields present. WLAN-GW is able to receive both encapsulation specified in RFC 1701 and RFC 2784, with all flag fields set to 0, and no optional fields present in the header.

Some of the advantages of soft-GRE:

  • Resources are only consumed on the WLAN-GW if there is one or more active subscriber on the AP. Merely broadcasting an SSID from an AP does not result in any state on the WLAN-GW.
  • No per-AP tunnel end-point configuration on WLAN-GW. This is important as the AP can get renumbered.
  • No control protocol to setup and maintain tunnel state on WLAN-GW. Soft-GRE tunnel termination is performed on dedicated IOMs with MS-ISAs (referred to as WLAN-GW IOM) Each slot requires two MS-ISAs dedicated for soft-GRE tunnel termination. MS-ISA provides tunnel encapsulation/de-capsulation, bandwidth shaping per tunnel (or per-tunnel per SSID), and anchor point for inter-AP mobility. The 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.
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