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jpereira edited this page Oct 17, 2014 · 14 revisions

softgre

Auto Provisioning for Tunnel GRE (Generic Routing Encapsulation)

-- Under development, not yet usable.

description

-- The idea is copied from Alcatel 7750

Layer 2 over Soft-GRE 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. Following are 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.

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.

**Build using Debian **

  1. my system used to devel, is a Debian 7.6 (wheezy) root@build:# lsb_release -a No LSB modules are available. Distributor ID: Debian Description: Debian GNU/Linux 7.6 (wheezy) Release: 7.6 Codename: wheezy root@build:#

  2. Install the development dependencies root@build:~# apt-get install git build-essential autoconf automake pkg-config

  3. now, install the softgre build dependencies root@build:~# apt-getinstall libdhash-dev libpcap-dev iproute-dev libapache2-mod-php5

  4. clone the project and build root@build:# git clone https://github.com/jpereira/softgre.git softgre.git root@build:# cd softgre.git root@build:# ./autogen.sh root@build:# ./configure root@build:# make root@build:# make install

  5. check the help of softgre root@build:~# softgred --help

  6. sample of settings Example: We have a interface 'eth0' there is a 'endpoint' of GRE tunnel, and we have a trunk interface 'eth1'. that can reach many vlans, like 2420,2421 and 2422. Now, we would like to attach with some vlans over GRE tunnel.

-> Create a bridge

ip link add br-vlan2420 type bridge

ip link add br-vlan2421 type bridge

ip link add br-vlan2422 type bridge

-> Create the local VLANs

ip link add link eth1 name eth1.2420 up type vlan id 2420

ip link add link eth1 name eth1.2421 up type vlan id 2421

ip link add link eth1 name eth1.2422 up type vlan id 2422

-> Attach the local VLANs with the bridges

ip link set eth1.2420 master br-vlan2420

ip link set eth1.2421 master br-vlan2421

ip link set eth1.2422 master br-vlan2422

-> Now, we can begin the provision!

softgred -ddd -i eth0 -a 10@br-vlan2420 -a 11@br-vlan2421 -a 12@br-vlan2422 1> /var/log/softgred.log 2>&1

-> Conclusion

Everything that arrive in GRE tunnel, will be forwarded to internals VLANs/bridge.

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