diff --git a/Makefile.dep b/Makefile.dep
index 5e40df93ee3eaac84daca5b124523c2661782ba1..2c14046231d11bd621345f2aabcbc9aa93551cc3 100644
--- a/Makefile.dep
+++ b/Makefile.dep
@@ -48,6 +48,11 @@ ifneq (,$(filter sixlowpan,$(USEMODULE)))
USEMODULE += vtimer
endif
+ifneq (,$(filter ng_sixlowpan_ctx,$(USEMODULE)))
+ USEMODULE += ng_ipv6_addr
+ USEMODULE += vtimer
+endif
+
ifneq (,$(filter ng_ipv6_hdr,$(USEMODULE)))
USEMODULE += ng_inet_csum
USEMODULE += ng_pktbuf
diff --git a/sys/Makefile b/sys/Makefile
index b734317e10306e874738b41b6e8cd92b618b4931..dd4b6ba0dce01b2fbbc5e6ec7d4c3cd79f6df724 100644
--- a/sys/Makefile
+++ b/sys/Makefile
@@ -92,6 +92,9 @@ endif
ifneq (,$(filter ng_pktbuf,$(USEMODULE)))
DIRS += net/crosslayer/ng_pktbuf
endif
+ifneq (,$(filter ng_sixlowpan_ctx,$(USEMODULE)))
+ DIRS += net/network_layer/ng_sixlowpan/ctx
+endif
ifneq (,$(filter netapi,$(USEMODULE)))
DIRS += net/crosslayer/netapi
endif
diff --git a/sys/include/net/ng_sixlowpan/ctx.h b/sys/include/net/ng_sixlowpan/ctx.h
new file mode 100644
index 0000000000000000000000000000000000000000..40e1544ebf92e3b3705839eebb6ba3c731fd2d16
--- /dev/null
+++ b/sys/include/net/ng_sixlowpan/ctx.h
@@ -0,0 +1,103 @@
+/*
+ * Copyright (C) 2015 Martine Lenders <mlenders@inf.fu-berlin.de>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @defgroup net_ng_sixlowpan_ctx Contexts for 6LoWPAN address compression
+ * @ingroup net_ng_sixlowpan
+ * @brief Context buffer for stateful 6LoWPAN address compression
+ * @see <a href="https://tools.ietf.org/html/rfc6282#section-3.1.2">
+ * RFC 6282, section 3.1.2
+ * </a>
+ * @see <a href="http://tools.ietf.org/html/rfc6775#section-4.2">
+ * RFC 6775, section 4.2
+ * </a>
+ * @{
+ *
+ * @file
+ * @brief Context buffer definitions
+ *
+ * @author Martine Lenders <mlenders@inf.fu-berlin.de>
+ */
+#ifndef NG_SIXLOWPAN_CTX_H_
+#define NG_SIXLOWPAN_CTX_H_
+
+#include <inttypes.h>
+
+#include "net/ng_ipv6/addr.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+#define NG_SIXLOWPAN_CTX_SIZE (16) /**< maximum number of entries in
+ * context buffer */
+
+typedef struct {
+ ng_ipv6_addr_t prefix; /**< The prefix associated to this context. */
+ uint8_t prefix_len; /**< Length of ng_sixlowpan_ctx_t::prefix in bit. */
+ /**
+ * @brief 4-bit Context ID.
+ *
+ * @note This needs to be here to easily translate prefixes to
+ * ID.
+ */
+ uint8_t id;
+ /**
+ * @brief Lifetime in minutes this context is valid.
+ *
+ * @see <a href="http://tools.ietf.org/html/rfc6775#section-4.2">
+ * 6LoWPAN Context Option
+ * </a>
+ */
+ uint16_t ltime;
+} ng_sixlowpan_ctx_t;
+
+/**
+ * @brief Gets a context matching the given IPv6 address best with its prefix.
+ *
+ * @param[in] addr An IPv6 address.
+ *
+ * @return The context associated with the best prefix for @p addr.
+ * @return NULL if there is no such context.
+ */
+ng_sixlowpan_ctx_t *ng_sixlowpan_ctx_lookup_addr(const ng_ipv6_addr_t *addr);
+
+/**
+ * @brief Gets context by ID.
+ *
+ * @param[in] id A context ID.
+ *
+ * @return The context associated with @p id.
+ * @return NULL if there is no such context.
+ */
+ng_sixlowpan_ctx_t *ng_sixlowpan_ctx_lookup_id(uint8_t id);
+
+/**
+ * @brief Updates (or adds if currently not registered) a context
+ *
+ * @param[in] id The ID for the context.
+ * Must be < @ref NG_SIXLOWPAN_CTX_SIZE.
+ * @param[in] prefix The prefix for the context.
+ * @param[in] prefix_len Length of @p prefix in bits. Must be > 0, when
+ * @p ltime > 0.
+ * @param[in] ltime New lifetime of the context. The context will
+ * be removed if 0.
+ *
+ * @return The new context on success.
+ * @return NULL, on error or on removal.
+ */
+ng_sixlowpan_ctx_t *ng_sixlowpan_ctx_update(uint8_t id, const ng_ipv6_addr_t *prefix,
+ uint8_t prefix_len, uint16_t ltime);
+
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* NG_SIXLOWPAN_CTX_H_ */
+/** @} */
diff --git a/sys/net/network_layer/ng_sixlowpan/ctx/Makefile b/sys/net/network_layer/ng_sixlowpan/ctx/Makefile
new file mode 100644
index 0000000000000000000000000000000000000000..afa4a1ee6dc5de5ecbd8a79cff16d8818618fd33
--- /dev/null
+++ b/sys/net/network_layer/ng_sixlowpan/ctx/Makefile
@@ -0,0 +1,3 @@
+MODULE = ng_sixlowpan_ctx
+
+include $(RIOTBASE)/Makefile.base
diff --git a/sys/net/network_layer/ng_sixlowpan/ctx/ng_sixlowpan_ctx.c b/sys/net/network_layer/ng_sixlowpan/ctx/ng_sixlowpan_ctx.c
new file mode 100644
index 0000000000000000000000000000000000000000..3bd57f68ef9820534608d369cad7eba6573944d8
--- /dev/null
+++ b/sys/net/network_layer/ng_sixlowpan/ctx/ng_sixlowpan_ctx.c
@@ -0,0 +1,172 @@
+/*
+ * Copyright (C) 2015 Martine Lenders <mlenders@inf.fu-berlin.de>
+ *
+ * This file is subject to the terms and conditions of the GNU Lesser
+ * General Public License v2.1. See the file LICENSE in the top level
+ * directory for more details.
+ */
+
+/**
+ * @{
+ *
+ * @file
+ */
+
+#include <stdbool.h>
+#include <inttypes.h>
+
+#include "mutex.h"
+#include "net/ng_sixlowpan/ctx.h"
+#include "vtimer.h"
+
+#define ENABLE_DEBUG (0)
+#include "debug.h"
+
+static ng_sixlowpan_ctx_t _ctxs[NG_SIXLOWPAN_CTX_SIZE];
+static uint32_t _ctx_inval_times[NG_SIXLOWPAN_CTX_SIZE];
+static mutex_t _ctx_mutex = MUTEX_INIT;
+
+static uint32_t _current_minute(void);
+static void _update_lifetime(unsigned int id);
+
+#if ENABLE_DEBUG
+static char ipv6str[NG_IPV6_ADDR_MAX_STR_LEN];
+#endif
+
+static inline bool _still_valid(unsigned int id)
+{
+ _update_lifetime(id);
+ return (_ctxs[id].ltime > 0);
+}
+
+ng_sixlowpan_ctx_t *ng_sixlowpan_ctx_lookup_addr(const ng_ipv6_addr_t *addr)
+{
+ uint8_t best = 0;
+ ng_sixlowpan_ctx_t *res = NULL;
+
+ mutex_lock(&_ctx_mutex);
+
+ for (unsigned int id = 0; id < NG_SIXLOWPAN_CTX_SIZE; id++) {
+ if (_still_valid(id)) {
+ uint8_t match = ng_ipv6_addr_match_prefix(&_ctxs[id].prefix, addr);
+
+ if ((_ctxs[id].prefix_len <= match) && (match > best)) {
+ best = match;
+ res = _ctxs + id;
+ }
+ }
+ }
+
+ mutex_unlock(&_ctx_mutex);
+
+#if ENABLE_DEBUG
+ if (res != NULL) {
+ DEBUG("6lo ctx: found context (%u, %s/%" PRIu8 ") ", res->id,
+ ng_ipv6_addr_to_str(ipv6str, &res->prefix, sizeof(ipv6str)),
+ res->prefix_len);
+ DEBUG("for address %s\n", ng_ipv6_addr_to_str(ipv6str, addr, sizeof(ipv6str)));
+ }
+#endif
+
+ return res;
+}
+
+ng_sixlowpan_ctx_t *ng_sixlowpan_ctx_lookup_id(uint8_t id)
+{
+ if (id >= NG_SIXLOWPAN_CTX_SIZE) {
+ return NULL;
+ }
+
+ mutex_lock(&_ctx_mutex);
+
+ if (_still_valid((unsigned int)id)) {
+ DEBUG("6lo ctx: found context (%u, %s/%" PRIu8 ")\n", id,
+ ng_ipv6_addr_to_str(ipv6str, &_ctxs[id].prefix, sizeof(ipv6str)),
+ _ctxs[id].prefix_len);
+ mutex_unlock(&_ctx_mutex);
+ return _ctxs + id;
+ }
+
+ mutex_unlock(&_ctx_mutex);
+
+ return NULL;
+}
+
+ng_sixlowpan_ctx_t *ng_sixlowpan_ctx_update(uint8_t id, const ng_ipv6_addr_t *prefix,
+ uint8_t prefix_len, uint16_t ltime)
+{
+ if ((id >= NG_SIXLOWPAN_CTX_SIZE)) {
+ return NULL;
+ }
+
+ mutex_lock(&_ctx_mutex);
+
+ _ctxs[id].ltime = ltime;
+
+ if (ltime == 0) {
+ mutex_unlock(&_ctx_mutex);
+ DEBUG("6lo ctx: remove context (%u, %s/%" PRIu8 ")\n", id,
+ ng_ipv6_addr_to_str(ipv6str, &_ctxs[id].prefix, sizeof(ipv6str)),
+ _ctxs[id].prefix_len);
+ return NULL;
+ }
+
+ /* test prefix_len now so that invalidation is possible regardless of the
+ * value. */
+ if (prefix_len == 0) {
+ mutex_unlock(&_ctx_mutex);
+ _ctxs[id].ltime = 0;
+ return NULL;
+ }
+
+ if (prefix_len > NG_IPV6_ADDR_BIT_LEN) {
+ _ctxs[id].prefix_len = NG_IPV6_ADDR_BIT_LEN;
+ }
+ else {
+ _ctxs[id].prefix_len = prefix_len;
+ }
+
+ _ctxs[id].id = id;
+
+ if (!ng_ipv6_addr_equal(&(_ctxs[id].prefix), prefix)) {
+ ng_ipv6_addr_set_unspecified(&(_ctxs[id].prefix));
+ ng_ipv6_addr_init_prefix(&(_ctxs[id].prefix), prefix,
+ _ctxs[id].prefix_len);
+ }
+ DEBUG("6lo ctx: update context (%u, %s/%" PRIu8 "), lifetime: %" PRIu16 " min\n",
+ id, ng_ipv6_addr_to_str(ipv6str, &_ctxs[id].prefix, sizeof(ipv6str)),
+ _ctxs[id].prefix_len, _ctxs[id].ltime);
+ _ctx_inval_times[id] = ltime + _current_minute();
+
+ mutex_unlock(&_ctx_mutex);
+
+ return _ctxs + id;
+}
+
+static uint32_t _current_minute(void)
+{
+ timex_t now;
+ vtimer_now(&now);
+ return now.seconds / 60;
+}
+
+static void _update_lifetime(unsigned int id)
+{
+ uint32_t now;
+
+ if (_ctxs[id].ltime == 0) {
+ return;
+ }
+
+ now = _current_minute();
+
+ if (now >= _ctx_inval_times[id]) {
+ DEBUG("6lo ctx: context %u was invalidated\n", id);
+ _ctxs[id].ltime = 0;
+ }
+ else {
+ _ctxs[id].ltime = (uint16_t)(_ctx_inval_times[id] - now);
+ }
+}
+
+/** @} */