Journal of Software Engineering and Applications, 2011, 4, 379-387
doi:10.4236/jsea.2011.46043 Published Online June 2011 (
Copyright © 2011 SciRes. JSEA
Stack E6 and Its Implementation within Linux
Dmitry Anatoly Zaitsev, Kyril Dmitry Guliaiev
Department of Computer Science, International Humanitarian University, Odessa, Ukraine.
Received February 5th, 2010; revised March 18th, 2 0 1 1; accepted April 16th, 2011.
The first implemen tation of new E6 stack of networking protocols within the kernel of an operating system is presented.
Stack E6 was developed to increase the efficiency of a network entirely built on the base of Ethernet technology. It uses
a uniform hierarchical E6 address on all the levels and annuls TCP, UDP and IP protocols. The experimental imple-
mentation adds a new system call to the kernel of Linux and a new type of Ethernet E6 frame. All the application in ter-
face standards are saved according to RFC except of E6 address usage instead of IP address and instead of Ethernet
MAC address as well.
Keywords: Stack of Protocols, E6, Linux, Kernel, System Call, Ethernet
1. Introduction
Stack of protocols E6 was presented in [1] then the cor-
responding patent of Ukraine on utility model [2] was
obtained and the robustness of E6 networks was ac-
knowledged [3] via modeling in CPN Tools. The next
steps assume its implementation within real-life operat-
ing systems and the development of special hardware
namely switching routers E6 (SRE6). On the periphery of
E6 network usual Ethernet switches could be employed
but the maximal efficiency supposes special hardware
Linux kernels are open source, making implementation
of the new protocol stacks possible. Different approaches
could be chosen but the present implementation is de-
veloped as an independent one without the integration
with Unix socket facilities. This approach is justified by
the fact that Unix sockets are rather heavy and closely
related with TCP/IP protocols family while the stack E6
does not use their facilities. The only requirement was to
save the application interfaces providing the further ad-
aptation of TCP/IP application software into E6 net-
Thus the main principle of the implementation was to
provide the application interface according to TCP and
UDP standards [4,5] and the interface according to
Ethernet standards [6] as well as independent work of
stack E6 among other protocols. Ethernet frames are
multiplexed/demultiplexed using the type field with new
value 0xE600 which corresponds to E6 frames. The us-
age of TCP and UPD application interface standards [4,5]
provides the possibility of the code reuse in other oper-
ating systems. So this implementation within Linux ker-
nel could be considered rather non Unix-de pendent as
far as it is not based on the Unix socket facilities.
The present experimental implementation does not
employ Ethernet LLC2 facilities and provides the appli-
cation interfaces of UPD protocol only. The implementa-
tion of TCP application interfaces requires Ether-net
LLC2 sliding window procedures usage instead of TCP
protocol procedures and is the subject for future work.
2. An Overview of E6 Technology
E6 technology [1,2] is based on two pivotal ideas: to use
the same uniform hierarchical E6 address with the length
of 6 bytes (Figure 1) on all the levels of the open sys-
tems interconnection model and to employ Ethernet
LLC2 sliding window procedures instead of protocol
TCP for guaranteed deliv ery of in formatio n.
As result only the pair of software port numbers is left
to be put into the packet header (E6p2 header—Figure 2)
and the rest of job is shifted to the Ethernet Data-Link
layer by the E6 Concordance software (Figure 3). As for
additional QoS parameters, they could be put into VLAN
header of the frame. Actually E6 annuls TCP, UDP and
IP protocols and the reminder is 4 bytes of the E6p2
header. It annuls also the mapping of IP addresses into
Stack E6 and Its Implementation within Linux Kern e l
Figure 1. The format of E6 address.
Figure 2. The E6p2 header.
Figure 3. The stack of E6 protocols.
MAC addresses and corresponding ARP/RARP protocols
which consumes a bulk of time on hosts and routers.
As far as E6 address is hierarchical in the same way as
CIDR IP address it provides the world-wide network
construction at the expense of hosts and subnets ad-
dresses aggregation under common mask that considera-
bly reduces the address table size. Ethernet suffers from
its plain MAC addresses which overflow address tables
of switches because of each individual address should be
listed. As far as E6 address has the same length as
Ethernet MAC address (namely 6 octets) it can be put
directly into the address field of the Ethernet frame in-
stead of MAC address. Modern Ethernet adapters allow
the assigning new MAC address to the interface and E6
address is assigned.
To provide an indep endent existence of E6 technolog y
a new type of E6 Ethernet frames is introduced (0xE600).
Hosts running E6 stack accept E6 frames while other
hosts simply ignore them. Usual Ethernet switches de-
liver E6 frames freely because they do not analyze the
frame type field usually. Traditional IP routers will drop
unknown E6 packets occasionally delivered as result of
broadcasting. So E6 could exist with in Ethernet switched
To provide the scalability, special E6 switching routers
(SRE6) should be developed or at least implemented as
patches to the usual software of known routers. The sim-
plest SRE6 could be created on the base of Unix com-
puter with a few Ethernet cards.
The packet delivery scheme shown in Figure 4 illus-
trates the advantages of E6 technology: the same pair of
destination and source E6 addresses is constant through
the entire delivery path. SRE6 only analyze the destina-
tion E6 address and switch the packet to the destination
port; no add itional IP-MAC ad dresses mapping , no p ac ke t
overhead with more than 40 octets of TCP and IP head-
ers. The computational resources of the devices are saved
for higher performance and better QoS, which is espe-
cially significant for VoIP applications.
Note that, E6 technology is justified for the present
headers. The computational resources of the devices are
saved for higher performance and better QoS, which is
especially significant for VoIP applications.
Note that, E6 technology is justified for the present
Copyright © 2011 SciRes. JSEA
Stack E6 and Its Implementation within Linux Kern e l381
Figure 4. The E6 packet delivery scheme.
time and future tendencies — Ethernet dominates at
the layer: LAN—1, 10 Gbps, campus and metropolitan
networks—10 Gbps over DWDM, backbones—PBB,
access networks—last-mile-Ethernet, wireless—WiFi.
3. Application Interfaces
All the code was developed as a loadable Linux kernel
module E6udpmod.ko save the minor changes to the
static part of the kernel with the goal to add a new system
call. A conditional system call 324 with the name
E6_call was added to the static part of the kernel. This
conditional system call is devised to implement all the
present and future E6 application interface routines. The
static part of the kernel contains a pointer for the new
system call 324 (which is not used in version of
the kernel) to the dummy routine sys_E6call which
checks the pointer new_sys_E6call to the actual routine
and calls it in the case the pointer is not equal to NULL.
The pointer is initialized with the value NULL so when
E6updmod.ko module is unloaded nothing occurs except
sys_E6call could write messages into system log file
when it is called. The pointer new_sys_E6call is exp orted
by the kernel for the usage in modules. The details are
represented in Listing 1.
The rest of the work is done by the module E6udpmod.ko.
At initialization it sets th e pointer new_ sys_E6 call to the
actual entry routine as well as finds Ethernet device
E6_dev, copies its hardware address and registers a new
E6 packet handler (Listing 2).
After the statement new_sys_E6call = mod_sys_E6call
all the E6 system calls are handled by the routine
mod_sys_E6call which is situated within E6updmod.ko
and works as a dispatcher of conditional calls recognized
by their numbers defined by the variable call.
The interface at the application level is provided by the
library E6udplib (Listing 3) that contains user-end rou-
tines E6sendmsg, E6rcvmsg, E6regport, E6unregport,
E6waitmsg which finally exert system call 324 using
syscall routine from the standard library libc.
Listing 1. Implementation of new system call within kernel.
Copyright © 2011 SciRes. JSEA
Current Distortion Evaluation in Traction 4Q Constant Switching Frequency Converters
Listing 2. Implementation of conditional call within loadable module.
The set of routines E6sendmsg, E6rcvmsg, E6regport,
E6unregport, E6waitmsg completely satisfy the require-
ments of RFC 768 on application interface of UDP pro-
tocol. The interactio n between the software code situated
in the static part of the kernel, in the loadable module and
in the user-end library is illustrated in Figure 5.
User interface library E6udplib was employed for the
development of simple E6talk application which pro-
vides the exchange of textual messages within E6 net-
work on the base of switched Ethernet. The application
Copyright © 2011 SciRes. JSEA
Current Distortion Evaluation in Traction 4Q Constant Switching Frequency Converters 383
Listing 3. E6 user-end library.
successfully provides real-life communication which ac-
knowledges the robustness of the stack E6. To acknowl-
edge the efficiency of E6 technology before TCP/IP pro-
tocols family a lot of work should be done yet. A traffic
analyzer such as Wireshark allows the watching E6
Ethernet frames which are transmitted freely among oth-
er types of frames and do not hamper the work of other
protocols. So E6 network exists in a parallel world re-
garding TCP/IP till the gateways b etween E6 an d TCP/IP
networks will have been done which is the direction for
future work.
4. Interfaces
The interface with Ethernet hardware within Linux ker-
nel is provided by the struct net_device which contains
the device description and functions. The valid functions
are given by the set of pointers which point to the actual
routines of the current Ethernet driver; the basic routines
are: open, stop, hard_start_xmit. The structure net_device
contains the header of the output packets queue; the
packet is represented by struct sk_buff * skb.
Figure 5. The interaction between the user, kernel and mo-
dule software code.
Copyright © 2011 SciRes. JSEA
Stack E6 and Its Implementation within Linux Kern e l
Listing 4. Registering E6 packets within kernel.
The interfaces are left without changes but only used
for E6 Ethernet frames transmission. The multiplexing at
sending E6 packets is implemented via the new type of
E6 Ethernet frames ETH_P_E6 (Listing 4).
The module fills in sk_buff with the user data and E6
headers using ETH_P_E6 type of frame and calls
hard_start_xmit passing the buck to the Ethernet driver
for the transmitting of the packet throug h the media.
The receiving of E6 packet is more complicated be-
cause it is done by the Ethernet driver on hardware in-
terrupt. The driver allocates and fills in sk_buff with the
arrived packet and then provides the demultiplexing pro-
cedure based on the registered types of packets. The reg-
istration of the packet types is implemented with struct
packet_type and is represented in Listing 4.
So after the statement dev_add_pack in the module in-
itialization routine E6udpmod_init_module (Listing 2),
all the arrived packets of the type ETH_P_E6 are proc-
essed by E6_rcv routine situated within E6udpmod.ko
module. Thus the two way interfaces with the layer are
installed: for the sending E6 packets and for the receiving
E6 packets. Note that, E6 packets and corresponding E6
frames are transmitted independently among other types
of Ethernet frames. The scheme shown in Figure 6 ex-
plains the interfaces of E6udpmod.ko with the Ethernet
5. Internal Data Structures and Routines
Besides the described above initialization routine E6-
udpmod_init_module and the dispatcher of the condi-
tional system call 324 with the name mod_sys_E6call the
module E6udpmod.ko contains the following routines:
routines for the implementation of conditional calls
E6_sendmsg, E6_rcvmsg, E6_regport, E6_unregport,
E6_waitmsg; the routine for the processing of arrived E6
packets E6_rcv; the module exit routine E6udpmod_
cleanup_module. The interaction of the mentioned rou-
tines is shown in Figure 5.
Let us consider the basic data structures of the
E6udpmod.ko module. Note that according to RFC 768
the source port of an application should be registered.
Figure 6. The interfaces with the layer.
Messages can be sent only from a registered port as well
as messages can be received only to a registered port. So,
the basic data structure is the list of registered ports. As
the sending of a message is completely done during one
system call E6sendmsg, the queues of output packets are
not created within E6udpmod.ko module; sk_buff is al-
located, data copied from the user address space, E6
headers created and finally sk_buff is put into the driver
packet output queue via driver routine hard_start_xmit
At the arrival of a new E6 packet, E6_rcv routine is
called by the driver and the packet is put into the appro-
priate queue to the registered port. Routine E6_rcv puts
the packet to the tail of the queue; system call E6_
rcvmsg gets the packet from the head of the queue. When
the destination por t is unregistered (unknown) the packet
is dropped.
Thus two levels of queues are created: the queue of
registered ports and the queues of received packets (to
registered ports). Figure 7 shows the interconnection of
the basic data. The description of the corresponding data
structures is given in Listing 5.
Copyright © 2011 SciRes. JSEA
Stack E6 and Its Implementation within Linux Kern e l385
struct E6portq {
struct E6portq * next;
struct E6portq * prev;
u16 E6reg_port;
pid_t pid;
int qlen;
struct sk_buf * skbhead;
struct sk_buf * skbtail;
static struct E6portq * E6inpq_head = NULL;
static struct E6portq * E6inpq_tail = N ULL;
int E6_sendmsg( struct E6msg_buf __user *msg )
int len;
struct sk_buff *skb;
struct E6hdr *E6h;
struct ethhdr *eth;
unsigned long flags;
int rc=0;
copy_from_user(km, msg, sizeof(struct E6msg_buf)));
if( E6find_regport( E6src_port ) = = NULL )
return rc;
skb=alloc_skb(len+E6HEADSSPACE, GFP_KERNEL);
/* Copy data */
skb_reserve(skb, E6HEADSSPACE);
copy_from_user( skb_put(skb,len), km->E6data, len );
/* Build the E6P2 header. */
skb_push(skb, sizeof(struct E6hdr));
E6h = (struct E6hdr *)skb_transport_header(skb);
E6h->E6dst_port = htons( km->E6dst_port );
E6h->E6src_port = htons( km->E6src_port );
/* Build the E6Ethernet header */
skb_push(skb, ETH_HLEN);
eth = (struct ethhdr *)skb_mac_header(skb);
skb->protocol = eth->h_proto = htons(ETH_P_E6);
memcpy(eth->h_source, E6_myaddr, dev->addr_len);
memcpy(eth->h_dest, km->E6dst_addr, dev->addr_len);
/* Pass skb to the driver */
return rc;
Listing 5. Sending E6 messages via Ethernet driver.
Let us consider the sending of E6 messages in details
(Listing 5). Routine E6_sendmsg copies the message
header from the user address space (copy_from_user),
checks whether the source port is registered, allocates
skb, copies the data from the user address space, fills in
E6h and eth headers and passes skb to the driver (hard_
Bri ef descript ion of other routines i s gi v en i n Li sting 6.
Copyright © 2011 SciRes. JSEA
Stack E6 and Its Implementation within Linux Kern e l
int E6_getmsg( u16 __user *upn, struct E6msg_buf __user *msg )
// finds registered port with the number pn=*upn
// checks weather the port pn belongs to the current process
// checks weather the skb queue to the port pn is empty
// extracts the head element from s kb queue
// copies the message he ader and the data into the user data space
// frees skb
int E6_rcv(struct sk_buff *skb, st ruct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
// extracts the destination port number dp from skb
// finds registered port with the number dp; if unregistered, drops skb
// checks the skb queue limit; if exceeded, drops skb
// puts skb into the tail of port dp queue
// checks the waiting flag and wakes up the waiting process
int E6_waitmsg( u16 __user *upn )
// checks weather the port pn=*upn is registered and belongs to the current process
// checks the skb queue is empty; if empty, blocks the current processing
int E6_regport( u16 __user *upn )
// checks weather the port pn=*upn is re gistered; if yes, returns an error
// creates new E6portq record, fills it in and puts it to the registered ports queue
int E6_unregport( u16 __user *upn )
// checks weather the port pn=*upn is registered; if no, returns an error
// checks weather the port pn belongs to the current process; if no, returns an error
// frees all the skb in the queue to the por t pn (drops packets)
// extracts E6portq record from the list and frees it
void E6udpmod_cleanup_module(void)
// unregisters E6 packet type: dev_remove_pack(&E6_packet_type) ;
// unregisters module system call handler: new_sys_E6call = NULL;
// frees the ports list and the corresponding skb queues
Listing 6. Brief description of E6 module r outines.
Figure 7. The basic data structures.
Note that the shown fragments of code are rather simpli-
fied for the brevity, numerous checks of the routines re-
turn codes and corresponding actions on errors were
6. Conclusions
It was implemented the first kernel level E6 protocol
stacks on Linux, kernel version The robustness
of E6 network was confirmed by the successful running
of E6talk application among other networking applica-
tions and protocols.
The datagram mode of the communication was im-
plemented (UDP like). The implementation of the data
segment mode with the guaranteed delivery of informa-
tion (TCP like) on the base of Ethernet LLC2 is the di-
rection for future work as well as the building gateways
between E6 and TCP/IP networks which exist now in
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Stack E6 and Its Implementation within Linux Kern e l387
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Copyright © 2011 SciRes. JSEA