/*! \file gprs_ns.c
* GPRS Networks Service (NS) messages on the Gb interface.
* 3GPP TS 08.16 version 8.0.1 Release 1999 / ETSI TS 101 299 V8.0.1 (2002-05). */
/*
* (C) 2009-2017 by Harald Welte <laforge@gnumonks.org>
* (C) 2016-2017 sysmocom - s.f.m.c. GmbH
*
* All Rights Reserved
*
* SPDX-License-Identifier: GPL-2.0+
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <http://www.gnu.org/licenses/>.
*
*/
/*! \addtogroup libgb
* @{
*
* GPRS Networks Service (NS) messages on the Gb interface
* 3GPP TS 08.16 version 8.0.1 Release 1999 / ETSI TS 101 299 V8.0.1 (2002-05)
*
* Some introduction into NS: NS is used typically on top of frame relay,
* but in the ip.access world it is encapsulated in UDP packets. It serves
* as an intermediate shim betwen BSSGP and the underlying medium. It doesn't
* do much, apart from providing congestion notification and status indication.
*
* Terms:
*
* NS Network Service
* NSVC NS Virtual Connection
* NSEI NS Entity Identifier
* NSVL NS Virtual Link
* NSVLI NS Virtual Link Identifier
* BVC BSSGP Virtual Connection
* BVCI BSSGP Virtual Connection Identifier
* NSVCG NS Virtual Connection Goup
* Blocked NS-VC cannot be used for user traffic
* Alive Ability of a NS-VC to provide communication
*
* There can be multiple BSSGP virtual connections over one (group of) NSVC's. BSSGP will
* therefore identify the BSSGP virtual connection by a BVCI passed down to NS.
* NS then has to firgure out which NSVC's are responsible for this BVCI.
* Those mappings are administratively configured.
*
* This implementation has the following limitations:
* - Only one NS-VC for each NSE: No load-sharing function
* - NSVCI 65535 and 65534 are reserved for internal use
* - Only UDP is supported as of no
