diff --git a/repos/os/include/net/arp.h b/repos/os/include/net/arp.h
index 17310000f..77e0e85aa 100644
--- a/repos/os/include/net/arp.h
+++ b/repos/os/include/net/arp.h
@@ -57,19 +57,15 @@ class Net::Arp_packet
 {
 	private:
 
-		/***********************
-		 ** ARP header fields **
-		 ***********************/
-
-		Genode::uint16_t _hw_addr_type;
-		Genode::uint16_t _prot_addr_type;
-		Genode::uint8_t  _hw_addr_sz;
-		Genode::uint8_t  _prot_addr_sz;
+		Genode::uint16_t _hardware_address_type;
+		Genode::uint16_t _protocol_address_type;
+		Genode::uint8_t  _hardware_address_size;
+		Genode::uint8_t  _protocol_address_size;
 		Genode::uint16_t _opcode;
-		Genode::uint8_t  _src_mac_addr[Ethernet_frame::ADDR_LEN];
-		Genode::uint8_t  _src_ip_addr[Ipv4_packet::ADDR_LEN];
-		Genode::uint8_t  _dst_mac_addr[Ethernet_frame::ADDR_LEN];
-		Genode::uint8_t  _dst_ip_addr[Ipv4_packet::ADDR_LEN];
+		Genode::uint8_t  _src_mac[Ethernet_frame::ADDR_LEN];
+		Genode::uint8_t  _src_ip[Ipv4_packet::ADDR_LEN];
+		Genode::uint8_t  _dst_mac[Ethernet_frame::ADDR_LEN];
+		Genode::uint8_t  _dst_ip[Ipv4_packet::ADDR_LEN];
 
 	public:
 
@@ -166,127 +162,29 @@ class Net::Arp_packet
 		}
 
 
-		/******************************
-		 ** ARP field read-accessors **
-		 ******************************/
+		/***************
+		 ** Accessors **
+		 ***************/
 
-		/**
-		 * \return link layer type (Arp_packet::Hardware_type).
-		 */
-		Genode::uint16_t hardware_address_type() {
-			return host_to_big_endian(_hw_addr_type); }
+		Genode::uint16_t hardware_address_type() const { return host_to_big_endian(_hardware_address_type); }
+		Genode::uint16_t protocol_address_type() const { return host_to_big_endian(_protocol_address_type); }
+		Genode::uint8_t  hardware_address_size() const { return _hardware_address_size; }
+		Genode::uint8_t  protocol_address_size() const { return _protocol_address_size; }
+		Genode::uint16_t opcode()                const { return host_to_big_endian(_opcode); }
+		Mac_address      src_mac()               const { return Mac_address((void *)&_src_mac); }
+		Ipv4_address     src_ip()                const { return Ipv4_address((void *)&_src_ip); }
+		Mac_address      dst_mac()               const { return Mac_address((void *)&_dst_mac); }
+		Ipv4_address     dst_ip()                const { return Ipv4_address((void *)&_dst_ip); }
 
-		/**
-		 * \return network/internet layer type (Ether_frame::EtherType).
-		 */
-		Genode::uint16_t protocol_address_type() {
-			return host_to_big_endian(_prot_addr_type); }
-
-		/**
-		 * \return size in bytes of hardware address.
-		 */
-		Genode::uint8_t hardware_address_size() { return _hw_addr_sz; }
-
-		/**
-		 * \return size in bytes of protocol address.
-		 */
-		Genode::uint8_t protocol_address_size() { return _prot_addr_sz; }
-
-		/**
-		 * \return operation code (Arp_packet::Opcode).
-		 */
-		Genode::uint16_t opcode() const { return host_to_big_endian(_opcode); }
-
-		/**
-		 * \return source MAC address.
-		 */
-		Mac_address src_mac() const {
-			return Mac_address((void *)&_src_mac_addr); }
-
-		/**
-		 * \return source IP address.
-		 */
-		Ipv4_address src_ip() const {
-			return Ipv4_address((void *)&_src_ip_addr); }
-
-		/**
-		 * \return destination MAC address.
-		 */
-		Mac_address dst_mac() const {
-			return Mac_address((void *)&_dst_mac_addr); }
-
-		/**
-		 * \return destination IP address.
-		 */
-		Ipv4_address dst_ip() const {
-			return Ipv4_address((void *)&_dst_ip_addr); }
-
-
-		/******************************
-		 ** ARP field write-accessors **
-		 ******************************/
-
-		/**
-		 * \return link layer type (Arp_packet::Hardware_type).
-		 */
-		void hardware_address_type(Genode::uint16_t v) {
-			_hw_addr_type = host_to_big_endian(v); }
-
-		/**
-		 * \return network/internet layer type (Ether_frame::EtherType).
-		 */
-		void protocol_address_type(Genode::uint16_t v) {
-			_prot_addr_type = host_to_big_endian(v); }
-
-		/**
-		 * \return size in bytes of hardware address.
-		 */
-		void hardware_address_size(Genode::uint8_t v) { _hw_addr_sz = v; }
-
-		/**
-		 * \return size in bytes of protocol address.
-		 */
-		void protocol_address_size(Genode::uint8_t v) { _prot_addr_sz = v; }
-
-		/**
-		 * Set Operation code.
-		 *
-		 * \param opcode  Arp_packet::Opcode to set.
-		 */
-		void opcode(Genode::uint16_t opcode) {
-			_opcode = host_to_big_endian(opcode); }
-
-		/**
-		 * Set source MAC address.
-		 *
-		 * \param src_mac_addr  MAC address to set.
-		 */
-		void src_mac(Mac_address src_mac_addr) {
-			src_mac_addr.copy(&_src_mac_addr); }
-
-		/**
-		 * Set source IP address.
-		 *
-		 * \param src_ip_addr  IP address to set.
-		 */
-		void src_ip(Ipv4_address src_ip_addr) {
-			src_ip_addr.copy(&_src_ip_addr); }
-
-		/**
-		 * Set destination MAC address.
-		 *
-		 * \param src_mac_addr  MAC address to set.
-		 */
-		void dst_mac(Mac_address dst_mac_addr) {
-			dst_mac_addr.copy(&_dst_mac_addr); }
-
-		/**
-		 * Set destination IP address.
-		 *
-		 * \param src_ip_addr  IP address to set.
-		 */
-		void dst_ip(Ipv4_address dst_ip_addr) {
-			dst_ip_addr.copy(&_dst_ip_addr); }
+		void hardware_address_type(Genode::uint16_t v) { _hardware_address_type = host_to_big_endian(v); }
+		void protocol_address_type(Genode::uint16_t v) { _protocol_address_type = host_to_big_endian(v); }
+		void hardware_address_size(Genode::uint8_t v)  { _hardware_address_size = v; }
+		void protocol_address_size(Genode::uint8_t v)  { _protocol_address_size = v; }
+		void opcode(Genode::uint16_t v)                { _opcode = host_to_big_endian(v); }
+		void src_mac(Mac_address v)                    { v.copy(&_src_mac); }
+		void src_ip(Ipv4_address v)                    { v.copy(&_src_ip); }
+		void dst_mac(Mac_address v)                    { v.copy(&_dst_mac); }
+		void dst_ip(Ipv4_address v)                    { v.copy(&_dst_ip); }
 
 
 		/***************************
@@ -298,10 +196,10 @@ class Net::Arp_packet
 		 *         address resolution with respect to IPv4 addresses.
 		 */
 		bool ethernet_ipv4() const {
-			return (   host_to_big_endian(_hw_addr_type)   == ETHERNET
-			        && host_to_big_endian(_prot_addr_type) == (Genode::uint16_t)Ethernet_frame::Type::IPV4
-			        && _hw_addr_sz   == Ethernet_frame::ADDR_LEN
-			        && _prot_addr_sz == Ipv4_packet::ADDR_LEN);
+			return (   host_to_big_endian(_hardware_address_type) == ETHERNET
+			        && host_to_big_endian(_protocol_address_type) == (Genode::uint16_t)Ethernet_frame::Type::IPV4
+			        && _hardware_address_size == Ethernet_frame::ADDR_LEN
+			        && _protocol_address_size == Ipv4_packet::ADDR_LEN);
 		}
 
 
diff --git a/repos/os/include/net/dhcp.h b/repos/os/include/net/dhcp.h
index 6df51fd42..c37056109 100644
--- a/repos/os/include/net/dhcp.h
+++ b/repos/os/include/net/dhcp.h
@@ -67,19 +67,8 @@ class Net::Dhcp_packet
 
 		class No_dhcp_packet : Genode::Exception {};
 
-
-		class Client_hw_address
-		{
-			public:
-				Genode::uint8_t addr[16];
-		};
-
 	private:
 
-		/************************
-		 ** DHCP packet fields **
-		 ************************/
-
 		Genode::uint8_t   _op;
 		Genode::uint8_t   _htype;
 		Genode::uint8_t   _hlen;
@@ -91,18 +80,18 @@ class Net::Dhcp_packet
 		Genode::uint8_t   _yiaddr[Ipv4_packet::ADDR_LEN];
 		Genode::uint8_t   _siaddr[Ipv4_packet::ADDR_LEN];
 		Genode::uint8_t   _giaddr[Ipv4_packet::ADDR_LEN];
-		Client_hw_address _chaddr;
+		Genode::uint8_t   _chaddr[16];
 		Genode::uint8_t   _sname[64];
 		Genode::uint8_t   _file[128];
 		Genode::uint32_t  _magic_cookie;
 		Genode::uint8_t   _opts[0];
 
-		enum Flag {
-			BROADCAST = 0x80
-		};
+		enum Flag { BROADCAST = 0x80 };
 
 	public:
 
+		enum class Htype : Genode::uint8_t { ETH = 1 };
+
 		/**
 		 * This class represents the data layout of an DHCP option.
 		 */
@@ -181,33 +170,47 @@ class Net::Dhcp_packet
 		}
 
 
-		/*******************************
-		 ** DHCP field read-accessors **
-		 *******************************/
+		/***************
+		 ** Accessors **
+		 ***************/
 
-		Genode::uint8_t  op()    const { return _op;                       }
-		Genode::uint8_t  htype() const { return _htype;                    }
-		Genode::uint8_t  hlen()  const { return _hlen;                     }
-		Genode::uint8_t  hops()  const { return _hops;                     }
-		Genode::uint32_t xid()   const { return host_to_big_endian(_xid);  }
-		Genode::uint16_t secs()  const { return host_to_big_endian(_secs); }
+		Genode::uint8_t   op()           const { return _op; }
+		Htype             htype()        const { return (Htype)_htype; }
+		Genode::uint8_t   hlen()         const { return _hlen; }
+		Genode::uint8_t   hops()         const { return _hops; }
+		Genode::uint32_t  xid()          const { return host_to_big_endian(_xid); }
+		Genode::uint16_t  secs()         const { return host_to_big_endian(_secs); }
+		bool              broadcast()    const { return _flags & BROADCAST; }
+		Ipv4_address      ciaddr()       const { return Ipv4_address((void *)_ciaddr);  }
+		Ipv4_address      yiaddr()       const { return Ipv4_address((void *)_yiaddr);  }
+		Ipv4_address      siaddr()       const { return Ipv4_address((void *)_siaddr);  }
+		Ipv4_address      giaddr()       const { return Ipv4_address((void *)_giaddr);  }
+		Mac_address       client_mac()   const { return Mac_address((void *)&_chaddr); }
+		char const       *server_name()  const { return (char const *)&_sname; }
+		char const       *file()         const { return (char const *)&_file;  }
+		Genode::uint32_t  magic_cookie() const { return host_to_big_endian(_magic_cookie); }
+		Genode::uint16_t  flags()        const { return host_to_big_endian(_flags); }
+		void             *opts()         const { return (void *)_opts; }
 
-		bool broadcast() { return _flags & BROADCAST;    }
+		void flags(Genode::uint16_t v) { _flags = host_to_big_endian(v); }
+		void file(const char* v)       { Genode::memcpy(_file, v, sizeof(_file));  }
+		void op(Genode::uint8_t v)     { _op = v; }
+		void htype(Htype v)            { _htype = (Genode::uint8_t)v; }
+		void hlen(Genode::uint8_t v)   { _hlen = v; }
+		void hops(Genode::uint8_t v)   { _hops = v; }
+		void xid(Genode::uint32_t v)   { _xid  = host_to_big_endian(v);  }
+		void secs(Genode::uint16_t v)  { _secs = host_to_big_endian(v); }
+		void broadcast(bool v)         { _flags = v ? BROADCAST : 0; }
+		void ciaddr(Ipv4_address v)    { v.copy(&_ciaddr); }
+		void yiaddr(Ipv4_address v)    { v.copy(&_yiaddr); }
+		void siaddr(Ipv4_address v)    { v.copy(&_siaddr); }
+		void giaddr(Ipv4_address v)    { v.copy(&_giaddr); }
+		void client_mac(Mac_address v) { v.copy(&_chaddr); }
 
-		Ipv4_address ciaddr() {
-			return Ipv4_address(&_ciaddr);  }
-		Ipv4_address yiaddr() {
-			return Ipv4_address(&_yiaddr);  }
-		Ipv4_address siaddr() const {
-			return Ipv4_address((void *)&_siaddr);  }
-		Ipv4_address giaddr() {
-			return Ipv4_address(&_giaddr);  }
 
-		Mac_address client_mac() const {
-			return Mac_address((void *)&_chaddr); }
-
-		const char* server_name()  { return (const char*) &_sname; }
-		const char* file()         { return (const char*) &_file;  }
+		/**********************
+		 ** Option utilities **
+		 **********************/
 
 		Option *option(Option_type op)
 		{
@@ -224,33 +227,6 @@ class Net::Dhcp_packet
 		}
 
 
-		/*******************************
-		 ** DHCP field write-accessors **
-		 *******************************/
-
-		void op(Genode::uint8_t op)       { _op = op;             }
-		void htype(Genode::uint8_t htype) { _htype = htype;       }
-		void hlen(Genode::uint8_t hlen)   { _hlen = hlen;         }
-		void hops(Genode::uint8_t hops)   { _hops = hops;         }
-		void xid(Genode::uint32_t xid)    { _xid = host_to_big_endian(_xid);   }
-		void secs(Genode::uint16_t secs)  { _secs = host_to_big_endian(_secs); }
-
-		void broadcast(bool broadcast) {
-			_flags = broadcast ? BROADCAST : 0;       }
-
-		void ciaddr(Ipv4_address ciaddr) {
-			ciaddr.copy(&_ciaddr); }
-		void yiaddr(Ipv4_address yiaddr) {
-			yiaddr.copy(&_yiaddr); }
-		void siaddr(Ipv4_address siaddr) {
-			siaddr.copy(&_siaddr); }
-		void giaddr(Ipv4_address giaddr) {
-			giaddr.copy(&_giaddr); }
-
-		void client_mac(Mac_address mac) {
-			mac.copy(&_chaddr); }
-
-
 		/*************************
 		 ** Convenience methods **
 		 *************************/
diff --git a/repos/os/include/net/ethernet.h b/repos/os/include/net/ethernet.h
index f94984dc5..fa52272d2 100644
--- a/repos/os/include/net/ethernet.h
+++ b/repos/os/include/net/ethernet.h
@@ -54,10 +54,10 @@ class Net::Ethernet_frame
 
 	private:
 
-		Genode::uint8_t  _dst_mac[ADDR_LEN]; /* destination mac address */
-		Genode::uint8_t  _src_mac[ADDR_LEN]; /* source mac address */
-		Genode::uint16_t _type;              /* encapsulated protocol */
-		unsigned         _data[0];           /* encapsulated data */
+		Genode::uint8_t  _dst[ADDR_LEN]; /* destination mac address */
+		Genode::uint8_t  _src[ADDR_LEN]; /* source mac address */
+		Genode::uint16_t _type;          /* encapsulated protocol */
+		unsigned         _data[0];       /* encapsulated data */
 
 	public:
 
@@ -85,56 +85,19 @@ class Net::Ethernet_frame
 		}
 
 
-		/***********************************
-		 ** Ethernet field read-accessors **
-		 ***********************************/
+		/***************
+		 ** Accessors **
+		 ***************/
 
-		/**
-		 * \return destination MAC address of frame.
-		 */
-		Mac_address dst() const { return Mac_address((void *)&_dst_mac); }
+		Mac_address                    dst()  const { return Mac_address((void *)_dst); }
+		Mac_address                    src()  const { return Mac_address((void *)_src); }
+		Type                           type() const { return (Type)host_to_big_endian(_type); }
+		template <typename T> T const *data() const { return (T const *)(_data); }
+		template <typename T> T       *data()       { return (T *)(_data); }
 
-		/**
-		 * \return source MAC address of frame.
-		 */
-		Mac_address src() const { return Mac_address((void *)&_src_mac); }
-
-		/**
-		 * \return EtherType - type of encapsulated protocol.
-		 */
-		Type type() const { return (Type)host_to_big_endian(_type); }
-
-		/**
-		 * \return payload data.
-		 */
-		template <typename T> T *       data()       { return (T *)(_data); }
-		template <typename T> T const * data() const { return (T const *)(_data); }
-
-
-		/***********************************
-		 ** Ethernet field write-accessors **
-		 ***********************************/
-
-		/**
-		 * Set the destination MAC address of this frame.
-		 *
-		 * \param mac  MAC address to be set.
-		 */
-		void dst(Mac_address mac) { mac.copy(&_dst_mac); }
-
-		/**
-		 * Set the source MAC address of this frame.
-		 *
-		 * \param mac  MAC address to be set.
-		 */
-		void src(Mac_address mac) { mac.copy(&_src_mac); }
-
-		/**
-		 * Set type of encapsulated protocol.
-		 *
-		 * \param type  the EtherType to be set.
-		 */
-		void type(Type type) { _type = host_to_big_endian((Genode::uint16_t)type); }
+		void dst(Mac_address v) { v.copy(&_dst); }
+		void src(Mac_address v) { v.copy(&_src); }
+		void type(Type type)    { _type = host_to_big_endian((Genode::uint16_t)type); }
 
 
 		/***************
diff --git a/repos/os/include/net/ipv4.h b/repos/os/include/net/ipv4.h
index 4f3b74b52..2997cd746 100644
--- a/repos/os/include/net/ipv4.h
+++ b/repos/os/include/net/ipv4.h
@@ -91,16 +91,17 @@ class Net::Ipv4_packet
 
 		unsigned         _header_length   : 4;
 		unsigned         _version         : 4;
-		Genode::uint8_t  _diff_service;
+		unsigned         _diff_service    : 6;
+		unsigned         _ecn             : 2;
 		Genode::uint16_t _total_length;
 		Genode::uint16_t _identification;
 		unsigned         _flags           : 3;
 		unsigned         _fragment_offset : 13;
 		Genode::uint8_t  _time_to_live;
 		Genode::uint8_t  _protocol;
-		Genode::uint16_t _header_checksum;
-		Genode::uint8_t  _src_addr[ADDR_LEN];
-		Genode::uint8_t  _dst_addr[ADDR_LEN];
+		Genode::uint16_t _checksum;
+		Genode::uint8_t  _src[ADDR_LEN];
+		Genode::uint8_t  _dst[ADDR_LEN];
 		unsigned         _data[0];
 
 		/**
@@ -116,6 +117,12 @@ class Net::Ipv4_packet
 
 	public:
 
+		enum class Protocol : Genode::uint8_t
+		{
+			TCP = 6,
+			UDP = 17,
+		};
+
 		enum Precedence {
 			NETWORK_CONTROL      = 7,
 			INTERNETWORK_CONTROL = 6,
@@ -150,54 +157,40 @@ class Net::Ipv4_packet
 		}
 
 
-		/*******************************
-		 ** IPv4 field read-accessors **
-		 *******************************/
+		/***************
+		 ** Accessors **
+		 ***************/
 
-		Genode::uint8_t version() { return _version; }
+		Genode::size_t                  header_length()          const { return _header_length; }
+		Genode::uint8_t                 version()                const { return _version; }
+		Genode::uint8_t                 diff_service()           const { return _diff_service; }
+		Genode::uint8_t                 ecn()                    const { return _ecn; }
+		Genode::size_t                  total_length()           const { return host_to_big_endian(_total_length); }
+		Genode::uint16_t                identification()         const { return host_to_big_endian(_identification); }
+		Genode::uint8_t                 flags()                  const { return _flags; }
+		Genode::size_t                  fragment_offset()        const { return _fragment_offset; }
+		Genode::uint8_t                 time_to_live()           const { return _time_to_live; }
+		Protocol                        protocol()               const { return (Protocol)_protocol; }
+		Genode::uint16_t                checksum()               const { return host_to_big_endian(_checksum); }
+		Ipv4_address                    src()                    const { return Ipv4_address((void *)&_src); }
+		Ipv4_address                    dst()                    const { return Ipv4_address((void *)&_dst); }
+		template <typename T> T const * data()                   const { return (T const *)(_data); }
+		template <typename T> T *       data()                         { return (T *)(_data); }
 
-		/* returns the number of 32-bit words the header occupies */
-		Genode::uint8_t header_length() { return _header_length; }
-		Genode::uint8_t precedence()    { return _diff_service & PRECEDENCE; }
+		void header_length(Genode::size_t v)     { _header_length = v; }
+		void version(Genode::uint8_t v)          { _version = v; }
+		void diff_service(Genode::uint8_t v)     { _diff_service = v; ; }
+		void ecn(Genode::uint8_t v)              { _ecn = v; ; }
+		void total_length(Genode::size_t v)      { _total_length = host_to_big_endian((Genode::uint16_t)v); }
+		void identification(Genode::uint16_t v)  { _identification = host_to_big_endian(v); }
+		void flags(Genode::uint8_t v)            { _flags = v; ; }
+		void fragment_offset(Genode::size_t v)   { _fragment_offset = v; ; }
+		void time_to_live(Genode::uint8_t v)     { _time_to_live = v; }
+		void protocol(Protocol v)                { _protocol = (Genode::uint8_t)v; }
+		void checksum(Genode::uint16_t checksum) { _checksum = host_to_big_endian(checksum); }
+		void src(Ipv4_address v)                 { v.copy(&_src); }
+		void dst(Ipv4_address v)                 { v.copy(&_dst); }
 
-		bool low_delay()              { return _diff_service & DELAY;      }
-		bool high_throughput()        { return _diff_service & THROUGHPUT; }
-		bool high_reliability()       { return _diff_service & RELIABILITY;}
-		bool minimize_monetary_cost() { return _diff_service & COST;       }
-
-		Genode::uint16_t total_length()   { return host_to_big_endian(_total_length);   }
-		Genode::uint16_t identification() { return host_to_big_endian(_identification); }
-
-		bool no_fragmentation() { return _flags & NO_FRAGMENT;             }
-		bool more_fragments()   { return _flags & MORE_FRAGMENTS;          }
-
-		Genode::size_t   fragment_offset() { return _fragment_offset;      }
-		Genode::uint8_t  time_to_live()    { return _time_to_live;         }
-		Genode::uint8_t  protocol() const  { return _protocol;             }
-
-		Genode::uint16_t checksum() { return host_to_big_endian(_header_checksum); }
-
-		Ipv4_address dst() const { return Ipv4_address((void *)&_dst_addr); }
-		Ipv4_address src() const { return Ipv4_address((void *)&_src_addr); }
-
-		template <typename T> T const * header() const { return (T const *)(this); }
-		template <typename T> T *       data()         { return (T *)(_data); }
-		template <typename T> T const * data()   const { return (T const *)(_data); }
-
-		/********************************
-		 ** IPv4 field write-accessors **
-		 ********************************/
-
-		void version(Genode::size_t version)    { _version = version; }
-		void header_length(Genode::size_t len)  { _header_length = len; }
-
-		void total_length(Genode::uint16_t len) { _total_length = host_to_big_endian(len); }
-		void time_to_live(Genode::uint8_t ttl)  { _time_to_live = ttl; }
-
-		void checksum(Genode::uint16_t checksum) { _header_checksum = host_to_big_endian(checksum); }
-
-		void dst(Ipv4_address ip) { ip.copy(&_dst_addr); }
-		void src(Ipv4_address ip) { ip.copy(&_src_addr); }
 
 		/***************
 		 ** Operators **
diff --git a/repos/os/include/net/tcp.h b/repos/os/include/net/tcp.h
index 4ba6604ae..6c697d81c 100644
--- a/repos/os/include/net/tcp.h
+++ b/repos/os/include/net/tcp.h
@@ -46,14 +46,16 @@ class Net::Tcp_packet
 		uint16_t _dst_port;
 		uint32_t _seq_nr;
 		uint32_t _ack_nr;
-		uint8_t  _data_offset;
-		uint8_t  _flags;
+		unsigned _data_offset : 4;
+		unsigned _reserved    : 3;
+		unsigned _flags_msb   : 1;
+		uint8_t  _flags_lsb;
 		uint16_t _window_size;
 		uint16_t _checksum;
 		uint16_t _urgent_ptr;
 		uint32_t _data[0];
 
-		struct Flags : Genode::Register<8>
+		struct Flags : Genode::Register<16>
 		{
 			struct Fin : Bitfield<0, 1> { };
 			struct Syn : Bitfield<1, 1> { };
@@ -61,30 +63,46 @@ class Net::Tcp_packet
 			struct Psh : Bitfield<3, 1> { };
 			struct Ack : Bitfield<4, 1> { };
 			struct Urg : Bitfield<5, 1> { };
+			struct Ece : Bitfield<6, 1> { };
+			struct Crw : Bitfield<7, 1> { };
+			struct Ns  : Bitfield<8, 1> { };
 		};
 
 	public:
 
-		bool fin() const { return Flags::Fin::get(_flags); };
-		bool syn() const { return Flags::Syn::get(_flags); };
-		bool rst() const { return Flags::Rst::get(_flags); };
-		bool psh() const { return Flags::Psh::get(_flags); };
-		bool ack() const { return Flags::Ack::get(_flags); };
-		bool urg() const { return Flags::Urg::get(_flags); };
-
-		enum Protocol_id { IP_ID = 6 };
-
 		class No_tcp_packet : Exception {};
 
+
+		Tcp_packet(size_t size) {
+			if (size < sizeof(Tcp_packet)) { throw No_tcp_packet(); } }
+
+
+		/***************
+		 ** Accessors **
+		 ***************/
+
+		Port     src_port()    const { return Port(host_to_big_endian(_src_port)); }
+		Port     dst_port()    const { return Port(host_to_big_endian(_dst_port)); }
+		uint32_t seq_nr()      const { return host_to_big_endian(_seq_nr); }
+		uint32_t ack_nr()      const { return host_to_big_endian(_ack_nr); }
+		uint8_t  data_offset() const { return _data_offset; }
+		uint16_t flags()       const { return _flags_lsb | _flags_msb << 8; }
+		uint16_t window_size() const { return host_to_big_endian(_window_size); }
+		uint16_t checksum()    const { return host_to_big_endian(_checksum); }
+		uint16_t urgent_ptr()  const { return host_to_big_endian(_urgent_ptr); }
+		bool     ns()          const { return Flags::Ns::get(flags()); };
+		bool     ece()         const { return Flags::Ece::get(flags()); };
+		bool     crw()         const { return Flags::Crw::get(flags()); };
+		bool     fin()         const { return Flags::Fin::get(flags()); };
+		bool     syn()         const { return Flags::Syn::get(flags()); };
+		bool     rst()         const { return Flags::Rst::get(flags()); };
+		bool     psh()         const { return Flags::Psh::get(flags()); };
+		bool     ack()         const { return Flags::Ack::get(flags()); };
+		bool     urg()         const { return Flags::Urg::get(flags()); };
+
 		void src_port(Port p) { _src_port = host_to_big_endian(p.value); }
 		void dst_port(Port p) { _dst_port = host_to_big_endian(p.value); }
 
-		Port src_port()  const { return Port(host_to_big_endian(_src_port)); }
-		Port dst_port()  const { return Port(host_to_big_endian(_dst_port)); }
-		uint16_t flags() const { return host_to_big_endian(_flags); }
-
-		Tcp_packet(size_t size) {
-			if (size < sizeof(Tcp_packet)) { throw No_tcp_packet(); } }
 
 		/**
 		 * TCP checksum is calculated over the tcp datagram + an IPv4
@@ -111,7 +129,7 @@ class Net::Tcp_packet
 				uint16_t d = ip_dst.addr[i] << 8 | ip_dst.addr[i + 1];
 				sum += s + d;
 			}
-			uint8_t prot[] = { 0, IP_ID };
+			uint8_t prot[] = { 0, (uint8_t)Ipv4_packet::Protocol::TCP };
 			sum += host_to_big_endian(*(uint16_t *)&prot) + tcp_size;
 
 			/* sum up TCP packet itself */
diff --git a/repos/os/include/net/udp.h b/repos/os/include/net/udp.h
index c798c2e9f..c47d5a5b4 100644
--- a/repos/os/include/net/udp.h
+++ b/repos/os/include/net/udp.h
@@ -51,9 +51,6 @@ class Net::Udp_packet
 
 	public:
 
-		enum Protocol_id { IP_ID = 0x11 };
-
-
 		/**
 		 * Exception used to indicate protocol violation.
 		 */
@@ -71,20 +68,20 @@ class Net::Udp_packet
 		}
 
 
-		/******************************
-		 ** UDP field read-accessors **
-		 ******************************/
+		/***************
+		 ** Accessors **
+		 ***************/
 
-		Port             src_port() const { return Port(host_to_big_endian(_src_port)); }
-		Port             dst_port() const { return Port(host_to_big_endian(_dst_port)); }
-		Genode::uint16_t length()   const { return host_to_big_endian(_length);   }
-		Genode::uint16_t checksum() const { return host_to_big_endian(_checksum); }
+		Port                            src_port() const { return Port(host_to_big_endian(_src_port)); }
+		Port                            dst_port() const { return Port(host_to_big_endian(_dst_port)); }
+		Genode::uint16_t                length()   const { return host_to_big_endian(_length);   }
+		Genode::uint16_t                checksum() const { return host_to_big_endian(_checksum); }
+		template <typename T> T const * data()     const { return (T const *)(_data); }
+		template <typename T> T *       data()           { return (T *)(_data); }
 
-		void src_port(Port p) { _src_port = host_to_big_endian(p.value); }
-		void dst_port(Port p) { _dst_port = host_to_big_endian(p.value); }
-
-		template <typename T> T *       data()       { return (T *)(_data); }
-		template <typename T> T const * data() const { return (T const *)(_data); }
+		void length(Genode::uint16_t v) { _length = host_to_big_endian(v); }
+		void src_port(Port p)           { _src_port = host_to_big_endian(p.value); }
+		void dst_port(Port p)           { _dst_port = host_to_big_endian(p.value); }
 
 
 		/***************
@@ -127,7 +124,7 @@ class Net::Udp_packet
 				Genode::uint16_t d = dst.addr[i] << 8 | dst.addr[i + 1];
 				sum += s + d;
 			}
-			Genode::uint8_t prot[] = { 0, IP_ID };
+			Genode::uint8_t prot[] = { 0, (Genode::uint8_t)Ipv4_packet::Protocol::UDP };
 			sum += host_to_big_endian(*(Genode::uint16_t*)&prot) + length();
 
 			/*
diff --git a/repos/os/src/lib/net/ipv4.cc b/repos/os/src/lib/net/ipv4.cc
index 76ae764d6..5be75d3b4 100644
--- a/repos/os/src/lib/net/ipv4.cc
+++ b/repos/os/src/lib/net/ipv4.cc
@@ -26,11 +26,11 @@ void Net::Ipv4_packet::print(Genode::Output &output) const
 {
 	Genode::print(output, "\033[32mIPV4\033[0m ", src(), " > ", dst(), " ");
 	switch (protocol()) {
-	case Tcp_packet::IP_ID:
+	case Protocol::TCP:
 		Genode::print(output,
 		              *reinterpret_cast<Tcp_packet const *>(data<void>()));
 		break;
-	case Udp_packet::IP_ID:
+	case Protocol::UDP:
 		Genode::print(output,
 		              *reinterpret_cast<Udp_packet const *>(data<void>()));
 		break;
@@ -84,7 +84,7 @@ Ipv4_address Ipv4_packet::ip_from_string(const char *ip)
 
 Genode::uint16_t Ipv4_packet::calculate_checksum(Ipv4_packet const &packet)
 {
-	Genode::uint16_t const *data = packet.header<Genode::uint16_t>();
+	Genode::uint16_t const *data = (Genode::uint16_t *)&packet;
 	Genode::uint32_t const sum = host_to_big_endian(data[0])
 	                           + host_to_big_endian(data[1])
 	                           + host_to_big_endian(data[2])
diff --git a/repos/os/src/lib/net/stat.cc b/repos/os/src/lib/net/stat.cc
index f21a78ba2..8d0f287f4 100644
--- a/repos/os/src/lib/net/stat.cc
+++ b/repos/os/src/lib/net/stat.cc
@@ -30,7 +30,7 @@ enum Measurement::status Measurement::_check(Net::Ethernet_frame * eth,
 	Ipv4_packet *ip = new (eth->data<void>()) Ipv4_packet(size -
 	                                                sizeof(Ethernet_frame));
 
-	if (ip->protocol() != Udp_packet::IP_ID)
+	if (ip->protocol() != Ipv4_packet::Protocol::UDP)
 		return Measurement::UNKNOWN;
 
 	Udp_packet *udp = new (ip->data<void>()) Udp_packet(size - sizeof(Ethernet_frame)
diff --git a/repos/os/src/lib/net/tcp.cc b/repos/os/src/lib/net/tcp.cc
index 84617e8e3..60b6bc40f 100644
--- a/repos/os/src/lib/net/tcp.cc
+++ b/repos/os/src/lib/net/tcp.cc
@@ -27,5 +27,8 @@ void Net::Tcp_packet::print(Genode::Output &output) const
 	if (psh()) { Genode::print(output, "p"); }
 	if (ack()) { Genode::print(output, "a"); }
 	if (urg()) { Genode::print(output, "u"); }
+	if (ece()) { Genode::print(output, "e"); }
+	if (crw()) { Genode::print(output, "c"); }
+	if (ns())  { Genode::print(output, "n"); }
 	Genode::print(output, "' ");
 }
diff --git a/repos/os/src/server/nic_bridge/component.cc b/repos/os/src/server/nic_bridge/component.cc
index 5466ca0a7..cc22b5944 100644
--- a/repos/os/src/server/nic_bridge/component.cc
+++ b/repos/os/src/server/nic_bridge/component.cc
@@ -54,7 +54,7 @@ bool Session_component::handle_ip(Ethernet_frame *eth, Genode::size_t size)
 	Ipv4_packet *ip =
 		new (eth->data<void>()) Ipv4_packet(size - sizeof(Ethernet_frame));
 
-	if (ip->protocol() == Udp_packet::IP_ID)
+	if (ip->protocol() == Ipv4_packet::Protocol::UDP)
 	{
 		Udp_packet *udp = new (ip->data<void>())
 			Udp_packet(size - sizeof(Ipv4_packet));
diff --git a/repos/os/src/server/nic_bridge/nic.cc b/repos/os/src/server/nic_bridge/nic.cc
index 5e6ab1a04..5d99fde5b 100644
--- a/repos/os/src/server/nic_bridge/nic.cc
+++ b/repos/os/src/server/nic_bridge/nic.cc
@@ -70,7 +70,7 @@ bool Net::Nic::handle_ip(Ethernet_frame *eth, Genode::size_t size) {
 		Ipv4_packet(size - sizeof(Ethernet_frame));
 
 	/* is it an UDP packet ? */
-	if (ip->protocol() == Udp_packet::IP_ID)
+	if (ip->protocol() == Ipv4_packet::Protocol::UDP)
 	{
 		Udp_packet *udp = new (ip->data<void>())
 			Udp_packet(size - sizeof(Ipv4_packet));
diff --git a/repos/os/src/server/nic_router/domain.cc b/repos/os/src/server/nic_router/domain.cc
index 0b40e4166..cd21e37b2 100644
--- a/repos/os/src/server/nic_router/domain.cc
+++ b/repos/os/src/server/nic_router/domain.cc
@@ -13,7 +13,7 @@
 
 /* local includes */
 #include <configuration.h>
-#include <protocol_name.h>
+#include <l3_protocol.h>
 
 /* Genode includes */
 #include <util/xml_node.h>
diff --git a/repos/os/src/server/nic_router/interface.cc b/repos/os/src/server/nic_router/interface.cc
index ab16339e1..5cf0b0ec7 100644
--- a/repos/os/src/server/nic_router/interface.cc
+++ b/repos/os/src/server/nic_router/interface.cc
@@ -19,7 +19,7 @@
 /* local includes */
 #include <interface.h>
 #include <configuration.h>
-#include <protocol_name.h>
+#include <l3_protocol.h>
 
 using namespace Net;
 using namespace Genode;
@@ -54,13 +54,13 @@ static void _destroy_links(Link_side_tree &links,
 }
 
 
-static void _link_packet(uint8_t  const  prot,
-                         void    *const  prot_base,
-                         Link           &link,
-                         bool     const  client)
+static void _link_packet(L3_protocol  const  prot,
+                         void        *const  prot_base,
+                         Link               &link,
+                         bool         const  client)
 {
 	switch (prot) {
-	case Tcp_packet::IP_ID:
+	case L3_protocol::TCP:
 		if (client) {
 			static_cast<Tcp_link *>(&link)->client_packet(*(Tcp_packet *)(prot_base));
 			return;
@@ -68,77 +68,77 @@ static void _link_packet(uint8_t  const  prot,
 			static_cast<Tcp_link *>(&link)->server_packet(*(Tcp_packet *)(prot_base));
 			return;
 		}
-	case Udp_packet::IP_ID:
+	case L3_protocol::UDP:
 		static_cast<Udp_link *>(&link)->packet();
 		return;
 	default: throw Interface::Bad_transport_protocol(); }
 }
 
 
-static void _update_checksum(uint8_t       const prot,
+static void _update_checksum(L3_protocol   const prot,
                              void         *const prot_base,
                              size_t        const prot_size,
                              Ipv4_address  const src,
                              Ipv4_address  const dst)
 {
 	switch (prot) {
-	case Tcp_packet::IP_ID:
+	case L3_protocol::TCP:
 		((Tcp_packet *)prot_base)->update_checksum(src, dst, prot_size);
 		return;
-	case Udp_packet::IP_ID:
+	case L3_protocol::UDP:
 		((Udp_packet *)prot_base)->update_checksum(src, dst);
 		return;
 	default: throw Interface::Bad_transport_protocol(); }
 }
 
 
-static Port _dst_port(uint8_t const prot, void *const prot_base)
+static Port _dst_port(L3_protocol const prot, void *const prot_base)
 {
 	switch (prot) {
-	case Tcp_packet::IP_ID: return (*(Tcp_packet *)prot_base).dst_port();
-	case Udp_packet::IP_ID: return (*(Udp_packet *)prot_base).dst_port();
+	case L3_protocol::TCP: return (*(Tcp_packet *)prot_base).dst_port();
+	case L3_protocol::UDP: return (*(Udp_packet *)prot_base).dst_port();
 	default: throw Interface::Bad_transport_protocol(); }
 }
 
 
-static void _dst_port(uint8_t  const prot,
-                      void    *const prot_base,
-                      Port     const port)
+static void _dst_port(L3_protocol  const prot,
+                      void        *const prot_base,
+                      Port         const port)
 {
 	switch (prot) {
-	case Tcp_packet::IP_ID: (*(Tcp_packet *)prot_base).dst_port(port); return;
-	case Udp_packet::IP_ID: (*(Udp_packet *)prot_base).dst_port(port); return;
+	case L3_protocol::TCP: (*(Tcp_packet *)prot_base).dst_port(port); return;
+	case L3_protocol::UDP: (*(Udp_packet *)prot_base).dst_port(port); return;
 	default: throw Interface::Bad_transport_protocol(); }
 }
 
 
-static Port _src_port(uint8_t const prot, void *const prot_base)
+static Port _src_port(L3_protocol const prot, void *const prot_base)
 {
 	switch (prot) {
-	case Tcp_packet::IP_ID: return (*(Tcp_packet *)prot_base).src_port();
-	case Udp_packet::IP_ID: return (*(Udp_packet *)prot_base).src_port();
+	case L3_protocol::TCP: return (*(Tcp_packet *)prot_base).src_port();
+	case L3_protocol::UDP: return (*(Udp_packet *)prot_base).src_port();
 	default: throw Interface::Bad_transport_protocol(); }
 }
 
 
-static void _src_port(uint8_t  const prot,
-                      void    *const prot_base,
-                      Port     const port)
+static void _src_port(L3_protocol  const prot,
+                      void        *const prot_base,
+                      Port         const port)
 {
 	switch (prot) {
-	case Tcp_packet::IP_ID: ((Tcp_packet *)prot_base)->src_port(port); return;
-	case Udp_packet::IP_ID: ((Udp_packet *)prot_base)->src_port(port); return;
+	case L3_protocol::TCP: ((Tcp_packet *)prot_base)->src_port(port); return;
+	case L3_protocol::UDP: ((Udp_packet *)prot_base)->src_port(port); return;
 	default: throw Interface::Bad_transport_protocol(); }
 }
 
 
-static void *_prot_base(uint8_t const  prot,
-                        size_t  const  prot_size,
-                        Ipv4_packet   &ip)
+static void *_prot_base(L3_protocol const  prot,
+                        size_t      const  prot_size,
+                        Ipv4_packet       &ip)
 {
 	switch (prot) {
-	case Tcp_packet::IP_ID: return new (ip.data<void>()) Tcp_packet(prot_size);
-	case Udp_packet::IP_ID: return new (ip.data<void>()) Udp_packet(prot_size);
+	case L3_protocol::TCP: return new (ip.data<void>()) Tcp_packet(prot_size);
+	case L3_protocol::UDP: return new (ip.data<void>()) Udp_packet(prot_size);
 	default: throw Interface::Bad_transport_protocol(); }
 }
 
@@ -147,12 +147,12 @@ static void *_prot_base(uint8_t const  prot,
  ** Interface **
  ***************/
 
-void Interface::_pass_prot(Ethernet_frame &eth,
-                           size_t   const  eth_size,
-                           Ipv4_packet    &ip,
-                           uint8_t  const  prot,
-                           void    *const  prot_base,
-                           size_t   const  prot_size)
+void Interface::_pass_prot(Ethernet_frame       &eth,
+                           size_t         const  eth_size,
+                           Ipv4_packet          &ip,
+                           L3_protocol    const  prot,
+                           void          *const  prot_base,
+                           size_t         const  prot_size)
 {
 	_update_checksum(prot, prot_base, prot_size, ip.src(), ip.dst());
 	_pass_ip(eth, eth_size, ip);
@@ -168,33 +168,35 @@ void Interface::_pass_ip(Ethernet_frame &eth,
 }
 
 
-Forward_rule_tree &Interface::_forward_rules(uint8_t const prot) const
+Forward_rule_tree &
+Interface::_forward_rules(L3_protocol const prot) const
 {
 	switch (prot) {
-	case Tcp_packet::IP_ID: return _domain.tcp_forward_rules();
-	case Udp_packet::IP_ID: return _domain.udp_forward_rules();
+	case L3_protocol::TCP: return _domain.tcp_forward_rules();
+	case L3_protocol::UDP: return _domain.udp_forward_rules();
 	default: throw Bad_transport_protocol(); }
 }
 
 
-Transport_rule_list &Interface::_transport_rules(uint8_t const prot) const
+Transport_rule_list &
+Interface::_transport_rules(L3_protocol const prot) const
 {
 	switch (prot) {
-	case Tcp_packet::IP_ID: return _domain.tcp_rules();
-	case Udp_packet::IP_ID: return _domain.udp_rules();
+	case L3_protocol::TCP: return _domain.tcp_rules();
+	case L3_protocol::UDP: return _domain.udp_rules();
 	default: throw Bad_transport_protocol(); }
 }
 
 
 void
-Interface::_new_link(uint8_t                       const  protocol,
+Interface::_new_link(L3_protocol                   const  protocol,
                      Link_side_id                  const &local,
                      Pointer<Port_allocator_guard> const  remote_port_alloc,
                      Interface                           &remote_interface,
                      Link_side_id                  const &remote)
 {
 	switch (protocol) {
-	case Tcp_packet::IP_ID:
+	case L3_protocol::TCP:
 		{
 			Tcp_link &link = *new (_alloc)
 				Tcp_link(*this, local, remote_port_alloc, remote_interface,
@@ -208,7 +210,7 @@ Interface::_new_link(uint8_t                       const  protocol,
 			}
 			return;
 		}
-	case Udp_packet::IP_ID:
+	case L3_protocol::UDP:
 		{
 			Udp_link &link = *new (_alloc)
 				Udp_link(*this, local, remote_port_alloc, remote_interface,
@@ -226,32 +228,32 @@ Interface::_new_link(uint8_t                       const  protocol,
 }
 
 
-Link_side_tree &Interface::_links(uint8_t const protocol)
+Link_side_tree &Interface::_links(L3_protocol const protocol)
 {
 	switch (protocol) {
-	case Tcp_packet::IP_ID: return _tcp_links;
-	case Udp_packet::IP_ID: return _udp_links;
+	case L3_protocol::TCP: return _tcp_links;
+	case L3_protocol::UDP: return _udp_links;
 	default: throw Bad_transport_protocol(); }
 }
 
 
-void Interface::link_closed(Link &link, uint8_t const prot)
+void Interface::link_closed(Link &link, L3_protocol const prot)
 {
 	_closed_links(prot).insert(&link);
 }
 
 
-void Interface::dissolve_link(Link_side &link_side, uint8_t const prot)
+void Interface::dissolve_link(Link_side &link_side, L3_protocol const prot)
 {
 	_links(prot).remove(&link_side);
 }
 
 
-Link_list &Interface::_closed_links(uint8_t const protocol)
+Link_list &Interface::_closed_links(L3_protocol const protocol)
 {
 	switch (protocol) {
-	case Tcp_packet::IP_ID: return _closed_tcp_links;
-	case Udp_packet::IP_ID: return _closed_udp_links;
+	case L3_protocol::TCP: return _closed_tcp_links;
+	case L3_protocol::UDP: return _closed_udp_links;
 	default: throw Bad_transport_protocol(); }
 }
 
@@ -273,14 +275,14 @@ void Interface::_adapt_eth(Ethernet_frame          &eth,
 }
 
 
-void Interface::_nat_link_and_pass(Ethernet_frame      &eth,
-                                   size_t        const  eth_size,
-                                   Ipv4_packet         &ip,
-                                   uint8_t       const  prot,
-                                   void         *const  prot_base,
-                                   size_t        const  prot_size,
-                                   Link_side_id  const &local,
-                                   Interface           &interface)
+void Interface::_nat_link_and_pass(Ethernet_frame        &eth,
+                                   size_t          const  eth_size,
+                                   Ipv4_packet           &ip,
+                                   L3_protocol     const  prot,
+                                   void           *const  prot_base,
+                                   size_t          const  prot_size,
+                                   Link_side_id    const &local,
+                                   Interface             &interface)
 {
 	Pointer<Port_allocator_guard> remote_port_alloc;
 	try {
@@ -313,7 +315,7 @@ void Interface::_handle_ip(Ethernet_frame          &eth,
 
 	/* try to route via transport layer rules */
 	try {
-		uint8_t       const prot      = ip.protocol();
+		L3_protocol   const prot      = ip.protocol();
 		size_t        const prot_size = ip.total_length() - ip.header_length() * 4;
 		void         *const prot_base = _prot_base(prot, prot_size, ip);
 		Link_side_id  const local     = { ip.src(), _src_port(prot, prot_base),
@@ -327,7 +329,7 @@ void Interface::_handle_ip(Ethernet_frame          &eth,
 			Link_side &remote_side = client ? link.server() : link.client();
 			Interface &interface = remote_side.interface();
 			if(_config().verbose()) {
-				log("Using ", protocol_name(prot), " link: ", link); }
+				log("Using ", l3_protocol_name(prot), " link: ", link); }
 
 			_adapt_eth(eth, eth_size, remote_side.src_ip(), pkt, interface);
 			ip.src(remote_side.dst_ip());
@@ -349,7 +351,7 @@ void Interface::_handle_ip(Ethernet_frame          &eth,
 
 				Interface &interface = rule.domain().interface().deref();
 				if(_config().verbose()) {
-					log("Using forward rule: ", protocol_name(prot), " ", rule); }
+					log("Using forward rule: ", l3_protocol_name(prot), " ", rule); }
 
 				_adapt_eth(eth, eth_size, rule.to(), pkt, interface);
 				ip.dst(rule.to());
@@ -369,7 +371,7 @@ void Interface::_handle_ip(Ethernet_frame          &eth,
 
 			Interface &interface = permit_rule.domain().interface().deref();
 			if(_config().verbose()) {
-				log("Using ", protocol_name(prot), " rule: ", transport_rule,
+				log("Using ", l3_protocol_name(prot), " rule: ", transport_rule,
 				    " ", permit_rule); }
 
 			_adapt_eth(eth, eth_size, local.dst_ip, pkt, interface);
diff --git a/repos/os/src/server/nic_router/interface.h b/repos/os/src/server/nic_router/interface.h
index fedada3a0..69b801ba6 100644
--- a/repos/os/src/server/nic_router/interface.h
+++ b/repos/os/src/server/nic_router/interface.h
@@ -18,6 +18,7 @@
 #include <link.h>
 #include <arp_cache.h>
 #include <arp_waiter.h>
+#include <l3_protocol.h>
 
 /* Genode includes */
 #include <nic_session/nic_session.h>
@@ -63,15 +64,15 @@ class Net::Interface
 		Link_list           _closed_tcp_links;
 		Link_list           _closed_udp_links;
 
-		void _new_link(Genode::uint8_t               const  protocol,
+		void _new_link(L3_protocol                   const  protocol,
 		               Link_side_id                  const &local_id,
 		               Pointer<Port_allocator_guard> const  remote_port_alloc,
 		               Interface                           &remote_interface,
 		               Link_side_id                  const &remote_id);
 
-		Forward_rule_tree &_forward_rules(Genode::uint8_t const prot) const;
+		Forward_rule_tree &_forward_rules(L3_protocol const prot) const;
 
-		Transport_rule_list &_transport_rules(Genode::uint8_t const prot) const;
+		Transport_rule_list &_transport_rules(L3_protocol const prot) const;
 
 		void _handle_arp(Ethernet_frame &eth, Genode::size_t const eth_size);
 
@@ -94,7 +95,7 @@ class Net::Interface
 		void _nat_link_and_pass(Ethernet_frame         &eth,
 		                        Genode::size_t   const  eth_size,
 		                        Ipv4_packet            &ip,
-		                        Genode::uint8_t  const  prot,
+		                        L3_protocol      const  prot,
 		                        void            *const  prot_base,
 		                        Genode::size_t   const  prot_size,
 		                        Link_side_id     const &local_id,
@@ -107,7 +108,7 @@ class Net::Interface
 		void _pass_prot(Ethernet_frame         &eth,
 		                Genode::size_t   const  eth_size,
 		                Ipv4_packet            &ip,
-		                Genode::uint8_t  const  prot,
+		                L3_protocol      const  prot,
 		                void            *const  prot_base,
 		                Genode::size_t   const  prot_size);
 
@@ -117,9 +118,9 @@ class Net::Interface
 
 		void _continue_handle_eth(Packet_descriptor const &pkt);
 
-		Link_list &_closed_links(Genode::uint8_t const protocol);
+		Link_list &_closed_links(L3_protocol const protocol);
 
-		Link_side_tree &_links(Genode::uint8_t const protocol);
+		Link_side_tree &_links(L3_protocol const protocol);
 
 		Configuration &_config() const;
 
@@ -162,9 +163,9 @@ class Net::Interface
 
 		~Interface();
 
-		void link_closed(Link &link, Genode::uint8_t const prot);
+		void link_closed(Link &link, L3_protocol const prot);
 
-		void dissolve_link(Link_side &link_side, Genode::uint8_t const prot);
+		void dissolve_link(Link_side &link_side, L3_protocol const prot);
 
 
 		/*********
diff --git a/repos/os/src/server/nic_router/protocol_name.cc b/repos/os/src/server/nic_router/l3_protocol.cc
similarity index 75%
rename from repos/os/src/server/nic_router/protocol_name.cc
rename to repos/os/src/server/nic_router/l3_protocol.cc
index 3347218d2..8e8c93289 100644
--- a/repos/os/src/server/nic_router/protocol_name.cc
+++ b/repos/os/src/server/nic_router/l3_protocol.cc
@@ -1,5 +1,5 @@
 /*
- * \brief  Provide protocol names as Genode Cstring objects
+ * \brief  Utilities regarding layer 3 protocols in general
  * \author Martin Stein
  * \date   2016-08-19
  */
@@ -12,7 +12,7 @@
  */
 
 /* local includes */
-#include <protocol_name.h>
+#include <l3_protocol.h>
 #include <interface.h>
 
 /* Genode includes */
@@ -30,10 +30,10 @@ Cstring const &Net::udp_name() { return _udp_name; }
 Cstring const &Net::tcp_name() { return _tcp_name; }
 
 
-Cstring const &Net::protocol_name(uint8_t protocol)
+Cstring const &Net::l3_protocol_name(L3_protocol protocol)
 {
 	switch (protocol) {
-	case Tcp_packet::IP_ID: return tcp_name();
-	case Udp_packet::IP_ID: return udp_name();
+	case L3_protocol::TCP: return tcp_name();
+	case L3_protocol::UDP: return udp_name();
 	default: throw Interface::Bad_transport_protocol(); }
 }
diff --git a/repos/os/src/server/nic_router/protocol_name.h b/repos/os/src/server/nic_router/l3_protocol.h
similarity index 61%
rename from repos/os/src/server/nic_router/protocol_name.h
rename to repos/os/src/server/nic_router/l3_protocol.h
index ef3000d47..8a48262f0 100644
--- a/repos/os/src/server/nic_router/protocol_name.h
+++ b/repos/os/src/server/nic_router/l3_protocol.h
@@ -1,5 +1,5 @@
 /*
- * \brief  Provide protocol names as Genode Cstring objects
+ * \brief  Utilities regarding layer 3 protocols in general
  * \author Martin Stein
  * \date   2016-08-19
  */
@@ -11,19 +11,22 @@
  * under the terms of the GNU Affero General Public License version 3.
  */
 
-#ifndef _PROTOCOL_NAME_H_
-#define _PROTOCOL_NAME_H_
+#ifndef _L3_PROTOCOL_H_
+#define _L3_PROTOCOL_H_
 
 /* Genode includes */
+#include <net/ipv4.h>
 #include <base/stdint.h>
 
 namespace Genode { class Cstring; }
 
 namespace Net {
 
+	using L3_protocol = Ipv4_packet::Protocol;
+
 	Genode::Cstring const &tcp_name();
 	Genode::Cstring const &udp_name();
-	Genode::Cstring const &protocol_name(Genode::uint8_t protocol);
+	Genode::Cstring const &l3_protocol_name(L3_protocol protocol);
 }
 
-#endif /* _PROTOCOL_NAME_H_ */
+#endif /* _L3_PROTOCOL_H_ */
diff --git a/repos/os/src/server/nic_router/link.cc b/repos/os/src/server/nic_router/link.cc
index a1ec89425..b3a74a80f 100644
--- a/repos/os/src/server/nic_router/link.cc
+++ b/repos/os/src/server/nic_router/link.cc
@@ -18,7 +18,7 @@
 #include <link.h>
 #include <interface.h>
 #include <configuration.h>
-#include <protocol_name.h>
+#include <l3_protocol.h>
 
 using namespace Net;
 using namespace Genode;
@@ -117,7 +117,7 @@ Link::Link(Interface                           &cln_interface,
            Link_side_id                  const &srv_id,
            Timer::Connection                   &timer,
            Configuration                       &config,
-           uint8_t                       const  protocol)
+           L3_protocol                   const  protocol)
 :
 	_config(config),
 	_client(cln_interface, cln_id, *this),
@@ -143,12 +143,12 @@ void Link::dissolve()
 	_client._interface.dissolve_link(_client, _protocol);
 	_server._interface.dissolve_link(_server, _protocol);
 	if (_config.verbose()) {
-		log("Dissolve ", protocol_name(_protocol), " link: ", *this); }
+		log("Dissolve ", l3_protocol_name(_protocol), " link: ", *this); }
 
 	try {
 		_server_port_alloc.deref().free(_server.dst_port());
 		if (_config.verbose()) {
-			log("Free ", protocol_name(_protocol),
+			log("Free ", l3_protocol_name(_protocol),
 			    " port ", _server.dst_port(),
 			    " at ", _server.interface(),
 			    " that was used by ", _client.interface());
@@ -169,7 +169,7 @@ Tcp_link::Tcp_link(Interface                           &cln_interface,
                    Link_side_id                  const &srv_id,
                    Timer::Connection                   &timer,
                    Configuration                       &config,
-                   uint8_t                       const  protocol)
+                   L3_protocol                   const  protocol)
 :
 	Link(cln_interface, cln_id, srv_port_alloc, srv_interface, srv_id, timer,
 	     config, protocol)
@@ -230,7 +230,7 @@ Udp_link::Udp_link(Interface                           &cln_interface,
                    Link_side_id                  const &srv_id,
                    Timer::Connection                   &timer,
                    Configuration                       &config,
-                   uint8_t                       const  protocol)
+                   L3_protocol                   const  protocol)
 :
 	Link(cln_interface, cln_id, srv_port_alloc, srv_interface, srv_id, timer,
 	     config, protocol)
diff --git a/repos/os/src/server/nic_router/link.h b/repos/os/src/server/nic_router/link.h
index 56f5c5e2d..31123a536 100644
--- a/repos/os/src/server/nic_router/link.h
+++ b/repos/os/src/server/nic_router/link.h
@@ -23,6 +23,7 @@
 
 /* local includes */
 #include <pointer.h>
+#include <l3_protocol.h>
 
 namespace Net {
 
@@ -131,7 +132,7 @@ class Net::Link : public Link_list::Element
 		Link_side                            _server;
 		Timer::One_shot_timeout<Link>        _close_timeout;
 		Genode::Microseconds          const  _close_timeout_us;
-		Genode::uint8_t               const  _protocol;
+		L3_protocol                   const  _protocol;
 
 		void _handle_close_timeout(Genode::Duration);
 
@@ -148,7 +149,7 @@ class Net::Link : public Link_list::Element
 		     Link_side_id                  const &srv_id,
 		     Timer::Connection                   &timer,
 		     Configuration                       &config,
-		     Genode::uint8_t               const  protocol);
+		     L3_protocol                   const  protocol);
 
 		void dissolve();
 
@@ -190,7 +191,7 @@ class Net::Tcp_link : public Link
 		         Link_side_id                  const &srv_id,
 		         Timer::Connection                   &timer,
 		         Configuration                       &config,
-		         Genode::uint8_t               const  protocol);
+		         L3_protocol                   const  protocol);
 
 		void client_packet(Tcp_packet &tcp);
 
@@ -207,7 +208,7 @@ struct Net::Udp_link : Link
 	         Link_side_id                  const &srv_id,
 	         Timer::Connection                   &timer,
 	         Configuration                       &config,
-	         Genode::uint8_t               const  protocol);
+	         L3_protocol                   const  protocol);
 
 	void packet() { _packet(); }
 };
diff --git a/repos/os/src/server/nic_router/nat_rule.cc b/repos/os/src/server/nic_router/nat_rule.cc
index 425bbcdc7..abb6a6b9b 100644
--- a/repos/os/src/server/nic_router/nat_rule.cc
+++ b/repos/os/src/server/nic_router/nat_rule.cc
@@ -75,10 +75,10 @@ void Nat_rule::print(Output &output) const
 }
 
 
-Port_allocator_guard &Nat_rule::port_alloc(uint8_t const prot)
+Port_allocator_guard &Nat_rule::port_alloc(L3_protocol const prot)
 {
 	switch (prot) {
-	case Tcp_packet::IP_ID: return _tcp_port_alloc;
-	case Udp_packet::IP_ID: return _udp_port_alloc;
+	case L3_protocol::TCP: return _tcp_port_alloc;
+	case L3_protocol::UDP: return _udp_port_alloc;
 	default: throw Interface::Bad_transport_protocol(); }
 }
diff --git a/repos/os/src/server/nic_router/nat_rule.h b/repos/os/src/server/nic_router/nat_rule.h
index 5723a28ce..d0f9fad0b 100644
--- a/repos/os/src/server/nic_router/nat_rule.h
+++ b/repos/os/src/server/nic_router/nat_rule.h
@@ -17,6 +17,7 @@
 /* local includes */
 #include <port_allocator.h>
 #include <leaf_rule.h>
+#include <l3_protocol.h>
 
 /* Genode includes */
 #include <util/avl_string.h>
@@ -47,7 +48,7 @@ class Net::Nat_rule : public Leaf_rule,
 
 		Nat_rule &find_by_domain(Domain &domain);
 
-		Port_allocator_guard &port_alloc(Genode::uint8_t const prot);
+		Port_allocator_guard &port_alloc(L3_protocol const prot);
 
 
 		/*********
diff --git a/repos/os/src/server/nic_router/target.mk b/repos/os/src/server/nic_router/target.mk
index 298a1200f..9fb66be04 100644
--- a/repos/os/src/server/nic_router/target.mk
+++ b/repos/os/src/server/nic_router/target.mk
@@ -6,7 +6,7 @@ SRC_CC += arp_waiter.cc ip_rule.cc
 SRC_CC += component.cc port_allocator.cc forward_rule.cc
 SRC_CC += nat_rule.cc mac_allocator.cc main.cc
 SRC_CC += uplink.cc interface.cc arp_cache.cc configuration.cc
-SRC_CC += domain.cc protocol_name.cc direct_rule.cc link.cc
+SRC_CC += domain.cc l3_protocol.cc direct_rule.cc link.cc
 SRC_CC += transport_rule.cc leaf_rule.cc permit_rule.cc
 
 INC_DIR += $(PRG_DIR)