brian@ucsd.EDU (Brian Kantor) (02/20/88)
---
/*
* add name
*/
return success;
NEGATIVE NAME REGISTRATION RESPONSE:
NetBIOS Working Group [Page 53]
RFC 1002 March 1987
/*
* you lose ...
*/
return failure;
END /* case */
END /* no response */
ELSE
IF NOT response tid = request tid THEN
BEGIN
ignore response packet;
END
/*
* received a response to the "challenge"
* packet
*/
CASE packet type OF
POSITIVE NAME QUERY:
/*
* remote node still has name.
*/
return failure;
NEGATIVE NAME QUERY:
/*
* remote node no longer has name
*/
return success;
END /* case */
END /* end node challenge */
END /* case */
END /* response */
END /* procedure */
5.1.3.2. M-NODE ADD GROUP NAME
PROCEDURE add_group_name(newname)
/*
* Host initiated processing for a P node
*/
BEGIN
/*
* same as for a unique name, except that the
* request packet must indicate that a
NetBIOS Working Group [Page 54]
RFC 1002 March 1987
* group name claim is being made.
*/
...
G = GROUP;
...
/*
* send packet
*/
...
END
5.1.3.3. M-NODE FIND NAME
PROCEDURE find_name(name)
/*
* Host initiated processing for a M node
*/
BEGIN
/*
* check if any node on the broadcast
* area has the name
*/
REPEAT
/* build packet */
...
broadcast NAME QUERY REQUEST packet;
pause(BCAST_REQ_RETRY_TIMEOUT);
UNTIL response packet received OR
max transmit threshold exceeded
IF valid response received THEN
BEGIN
save response as authoritative response;
start_timer(CONFLICT_TIMER);
return success;
END
/*
* no valid response on the b'cast segment.
* Try the name server.
*/
REPEAT
NetBIOS Working Group [Page 55]
RFC 1002 March 1987
/*
* build packet
*/
ONT = M;
G = DONT CARE;
unicast NAME QUERY REQUEST packet to NBNS;
/*
* a NBNS node might send response packet
*/
IF receive a WACK RESPONSE THEN
pause(time from TTL field of response);
ELSE
pause(UCAST_REQ_RETRY_TIMEOUT);
UNTIL response packet received OR
max transmit threshold exceeded
IF no response packet received THEN
return failure;
ELSE
IF NOT response tid = request tid THEN
ignore packet;
ELSE
CASE packet type OF
POSITIVE NAME QUERY RESPONSE:
return success;
REDIRECT NAME QUERY RESPONSE:
/*
* NBNS node wants this end node
* to use some other NBNS node
* to resolve the query.
*/
repeat query with NBNS address
in the response packet;
NEGATIVE NAME QUERY RESPONSE:
return failure;
END /* case */
END /* procedure */
5.1.3.4. M-NODE DELETE NAME
PROCEDURE delete_name (name)
/*
NetBIOS Working Group [Page 56]
RFC 1002 March 1987
* Host initiated processing for a P node
*/
BEGIN
/*
* First, delete name on NBNS
*/
REPEAT
/*
* build packet
*/
...
/*
* send request
*/
unicast NAME RELEASE REQUEST packet to NBNS;
IF receive a WACK RESPONSE THEN
pause(time from TTL field of response);
ELSE
pause(UCAST_REQ_RETRY_TIMEOUT);
UNTIL retransmit count has been exceeded
or response been received
IF response has been received THEN
CASE packet type OF
POSITIVE NAME RELEASE RESPONSE:
/*
* Deletion of name on b'cast segment is deferred
* until after NBNS has deleted the name
*/
REPEAT
/* build packet */
...
broadcast NAME RELEASE REQUEST;
pause(BCAST_REQ_RETRY_TIMEOUT);
UNTIL rexmt threshold exceeded
return success;
NEGATIVE NAME RELEASE RESPONSE:
/*
* NBNS does want node to delete this
* name
*/
NetBIOS Working Group [Page 57]
RFC 1002 March 1987
return failure;
END /* case */
END /* procedure */
5.1.3.5. M-NODE INCOMING PACKET PROCESSING
Processing initiated by reception of packets at a M node
PROCEDURE process_incoming_packet(packet)
/*
* Processing initiated by incoming packets at a M node
*/
BEGIN
CASE packet type of
NAME CONFLICT DEMAND:
IF name exists in local name table THEN
mark name as in conflict;
return;
NAME QUERY REQUEST:
IF name exists in local name table THEN
BEGIN /* name exists */
/*
* build packet
*/
...
/*
* send response to the IP address and port
* number from which the request was received.
*/
send POSITIVE NAME QUERY RESPONSE ;
return;
END /* exists */
ELSE
BEGIN /* does not exist */
/*
* send response to the requestor
*/
IF request NOT broadcast THEN
/*
* Don't send negative responses to
* queries sent by B nodes
*/
NetBIOS Working Group [Page 58]
RFC 1002 March 1987
send NEGATIVE NAME QUERY RESPONSE ;
return;
END /* does not exist */
NODE STATUS REQUEST:
BEGIN
/*
* Name of "*" may be used for force node to
* divulge status for administrative purposes
*/
IF name in local name table OR name = "*" THEN
/*
* Build response packet and
* send to requestor node
* Send only those names that are
* in the same scope as the scope
* in the request packet.
*/
send NODE STATUS RESPONSE;
END
NAME RELEASE REQUEST:
/*
* This will be received if the NBNS wants to flush the
* name from the local name table, or from the local
* cache.
*/
IF name exists in the local name table THEN
BEGIN
delete name from local name table;
inform user that name has been deleted;
END
ELSE
IF name has been cached locally THEN
BEGIN
remove entry from cache:
END
NAME REGISTRATION REQUEST (UNIQUE):
IF name exists in local name table THEN
send NEGATIVE NAME REGISTRATION RESPONSE ;
NAME REGISTRATION REQUEST (GROUP):
IF name exists in local name table THEN
BEGIN
IF local entry is a unique name THEN
send NEGATIVE NAME REGISTRATION RESPONSE ;
END
END /* case */
END /* procedure */
NetBIOS Working Group [Page 59]
RFC 1002 March 1987
5.1.3.6. M-NODE TIMER INITIATED PROCESSING
Processing initiated by timer expiration:
PROCEDURE timer_expired()
/*
* Processing initiated by the expiration of a timer on a M node
*/
BEGIN
/*
* Send a NAME REFRESH REQUEST for each name which the
* TTL which has expired.
*/
REPEAT
build NAME REFRESH REQUEST packet;
REPEAT
send packet to NBNS;
IF receive a WACK RESPONSE THEN
pause(time from TTL field of response);
ELSE
pause(UCAST_REQ_RETRY_TIMEOUT);
UNTIL response packet is received or
retransmit count has been exceeded
CASE packet type OF
POSITIVE NAME REGISTRATION RESPONSE:
/* successfully refreshed */
reset TTL timer for this name;
NEGATIVE NAME REGISTRATION RESPONSE:
/*
* refused, can't keep name
* assume in conflict
*/
mark name as in conflict;
END /* case */
UNTIL request sent for all names for which TTL
has expired
END /* procedure */
5.1.4. NBNS ACTIVITY
A NBNS node will receive directed packets from P and M nodes.
Reply packets are always sent as directed packets to the source
IP address and UDP port number. Received broadcast packets must
be ignored.
NetBIOS Working Group [Page 60]
RFC 1002 March 1987
5.1.4.1. NBNS INCOMING PACKET PROCESSING
PROCEDURE process_incoming_packet(packet)
/*
* Incoming packet processing on a NS node
*/
BEGIN
IF packet was sent as a broadcast THEN
BEGIN
discard packet;
return;
END
CASE packet type of
NAME REGISTRATION REQUEST (UNIQUE):
IF unique name exists in data base THEN
BEGIN /* unique name exists */
/*
* NBNS node may be a "passive"
* server in that it expects the
* end node to do the challenge
* server. Such a NBNS node is
* called a "non-secure" server.
* A "secure" server will do the
* challenging before it sends
* back a response packet.
*/
IF non-secure THEN
BEGIN
/*
* build response packet
*/
...
/*
* let end node do the challenge
*/
send END-NODE CHALLENGE NAME REGISTRATION
RESPONSE;
return;
END
ELSE
/*
* secure server - do the name
* challenge operation
*/
NetBIOS Working Group [Page 61]
RFC 1002 March 1987
REPEAT
send NAME QUERY REQUEST;
pause(UCAST_REQ_RETRY_TIMEOUT);
UNTIL response has been received or
retransmit count has been exceeded
IF no response was received THEN
BEGIN
/* node down */
update data base - remove entry;
update data base - add new entry;
send POSITIVE NAME REGISTRATION RESPONSE;
return;
END
ELSE
BEGIN /* challenged node replied */
/*
* challenged node replied with
* a response packet
*/
CASE packet type
POSITIVE NAME QUERY RESPONSE:
/*
* name still owned by the
* challenged node
*
* build packet and send response
*/
...
/*
* Note: The NBNS will need to
* keep track (based on transaction id) of
* the IP address and port number
* of the original requestor.
*/
send NEGATIVE NAME REGISTRATION RESPONSE;
return;
NEGATIVE NAME QUERY RESPONSE:
update data base - remove entry;
update data base - add new entry;
/*
* build response packet and send
NetBIOS Working Group [Page 62]
RFC 1002 March 1987
* response
*/
send POSITIVE NAME REGISTRATION RESPONSE;
return;
END /* case */
END /* challenged node replied */
END /* unique name exists in data base */
ELSE
IF group name exists in data base THEN
BEGIN /* group names exists */
/*
* Members of a group name are NOT
* challenged.
* Make the assumption that
* at least some of the group members
* are still alive.
* Refresh mechanism will
* allow the NBNS to detect when all
* members of a group no longer use that
* name
*/
send NEGATIVE NAME REGISTRATION RESPONSE;
END /* group name exists */
ELSE
BEGIN /* name does not exist */
/*
* Name does not exist in data base
*
* This code applies to both non-secure
* and secure server.
*/
update data base - add new entry;
send POSITIVE NAME REGISTRATION RESPONSE;
return;
END
NAME QUERY REQUEST:
IF name exists in data base THEN
BEGIN
/*
* build response packet and send to
* requestor
*/
...
send POSITIVE NAME QUERY RESPONSE;
return;
NetBIOS Working Group [Page 63]
RFC 1002 March 1987
ELSE
BEGIN
/*
* build response packet and send to
* requestor
*/
...
send NEGATIVE NAME QUERY RESPONSE;
return;
END
NAME REGISTRATION REQUEST (GROUP):
IF name exists in data base THEN
BEGIN
IF local entry is a unique name THEN
BEGIN /* local is unique */
IF non-secure THEN
BEGIN
send END-NODE CHALLENGE NAME
REGISTRATION RESPONSE;
return;
END
REPEAT
send NAME QUERY REQUEST;
pause(UCAST_REQ_RETRY_TIMEOUT);
UNTIL response received or
retransmit count exceeded
IF no response received or
NEGATIVE NAME QUERY RESPONSE
received THEN
BEGIN
update data base - remove entry;
update data base - add new entry;
send POSITIVE NAME REGISTRATION RESPONSE;
return;
END
ELSE
BEGIN
/*
* name still being held
* by challenged node
*/
send NEGATIVE NAME REGISTRATION RESPONSE;
END
END /* local is unique */
ELSE
BEGIN /* local is group */
NetBIOS Working Group [Page 64]
RFC 1002 March 1987
/*
* existing entry is a group name
*/
update data base - remove entry;
update data base - add new entry;
send POSITIVE NAME REGISTRATION RESPONSE;
return;
END /* local is group */
END /* names exists */
ELSE
BEGIN /* does not exist */
/* name does not exist in data base */
update data base - add new entry;
send POSITIVE NAME REGISTRATION RESPONSE;
return;
END /* does not exist */
NAME RELEASE REQUEST:
/*
* secure server may choose to disallow
* a node from deleting a name
*/
update data base - remove entry;
send POSITIVE NAME RELEASE RESPONSE;
return;
NAME UPDATE REQUEST:
/*
* End-node completed a successful challenge,
* no update database
*/
IF secure server THEN
send NEGATIVE NAME REGISTRATION RESPONSE;
ELSE
BEGIN /* new entry */
IF entry already exists THEN
update data base - remove entry;
update data base - add new entry;
send POSITIVE NAME REGISTRATION RESPONSE;
start_timer(TTL);
END
NAME REFRESH REQUEST:
check for consistency;
NetBIOS Working Group [Page 65]
RFC 1002 March 1987
IF node not allowed to have name THEN
BEGIN
/*
* tell end node that it can't have name
*/
send NEGATIVE NAME REGISTRATION RESPONSE;
END
ELSE
BEGIN
/*
* send confirmation response to the
* end node.
*/
send POSITIVE NAME REGISTRATION;
start_timer(TTL);
END
return;
END /* case */
END /* procedure */
5.1.4.2. NBNS TIMER INITIATED PROCESSING
A NS node uses timers to flush out entries from the data base.
Each entry in the data base is removed when its timer expires.
This time value is a multiple of the refresh TTL established when
the name was registered.
PROCEDURE timer_expired()
/*
* processing initiated by expiration of TTL for a given name
*/
BEGIN
/*
* NBNS can (optionally) ensure
* that the node is actually down
* by sending a NODE STATUS REQUEST.
* If such a request is sent, and
* no response is received, it can
* be assumed that the node is down.
*/
remove entry from data base;
END
NetBIOS Working Group [Page 66]
RFC 1002 March 1987
5.2. SESSION SERVICE PROTOCOLS
The following are variables and should be configurable by the
NetBIOS user. The default values of these variables is found in
"Defined Constants and Variables" in the Detailed
Specification.):
- SSN_RETRY_COUNT - The maximum number TCP connection attempts
allowable per a single NetBIOS call request.
- SSN_CLOSE_TIMEOUT is the time period to wait when closing the
NetBIOS session before killing the TCP connection if session
sends are outstanding.
The following are Defined Constants for the NetBIOS Session
Service. (See "Defined Constants and Variables" in the Detailed
Specification for the value of these constants):
- SSN_SRVC_TCP_PORT - is the globally well-known TCP port
allocated for the NetBIOS Session Service. The service accepts
TCP connections on this port to establish NetBIOS Sessions.
The TCP connection established to this port by the caller is
initially used for the exchange of NetBIOS control information.
The actual NetBIOS data connection may also pass through this
port or, through the retargetting facility, through another
port.
5.2.1. SESSION ESTABLISHMENT PROTOCOLS
5.2.1.1. USER REQUEST PROCESSING
PROCEDURE listen(listening name, caller name)
/*
* User initiated processing for B, P and M nodes
*
* This procedure assumes that an incoming session will be
* retargetted here by a session server.
*/
BEGIN
Do TCP listen; /* Returns TCP port used */
Register listen with Session Service, give names and
TCP port;
Wait for TCP connection to open; /* Incoming call */
Read SESSION REQUEST packet from connection
Process session request (see section on
processing initiated by the reception of session
service packets);
NetBIOS Working Group [Page 67]
RFC 1002 March 1987
Inform Session Service that NetBIOS listen is complete;
IF session established THEN
return success and session information to user;
ELSE
return failure;
END /* procedure */
PROCEDURE call(calling name, called name)
/*
* user initiated processing for B, P and M nodes
*/
/*
* This algorithm assumes that the called name is a unique name.
* If the called name is a group name, the call() procedure
* needs to cycle through the members of the group
* until either (retry_count == SSN_RETRY_COUNT) or
* the list has been exhausted.
*/
BEGIN
retry_count = 0;
retarget = FALSE; /* TRUE: caller is being retargetted */
name_query = TRUE; /* TRUE: caller must begin again with */
/* name query. */
REPEAT
IF name_query THEN
BEGIN
do name discovery, returns IP address;
TCP port = SSN_SRVC_TCP_PORT;
IF name discovery fails THEN
return failure;
ELSE
name_query = FALSE;
END
/*
* now have IP address and TCP port of
* remote party.
*/
establish TCP connection with remote party, use an
ephemeral port as source TCP port;
IF connection refused THEN
BEGIN
IF retarget THEN
BEGIN
/* retry */
retarget = FALSE;
NetBIOS Working Group [Page 68]
RFC 1002 March 1987
use original IP address and TCP port;
goto LOOP;
END
/* retry for just missed TCP listen */
pause(SESSION_RETRY_TIMER);
establish TCP connection, again use ephemeral
port as source TCP port;
IF connection refused OR
connection timed out THEN
return failure;
END
ELSE
IF connection timed out THEN
BEGIN
IF retarget THEN
BEGIN
/* retry */
retarget = FALSE;
use original IP address and TCP port;
goto LOOP;
END
ELSE
BEGIN
/*
* incorrect name discovery was done,
* try again
*/
inform name discovery process of
possible error;
name_query = TRUE;
goto LOOP;
END
END
/*
* TCP connection has been established
*/
wait for session response packet;
CASE packet type OF
POSITIVE SESSION RESPONSE:
return success and session established
information;
NEGATIVE SESSION RESPONSE:
BEGIN
NetBIOS Working Group [Page 69]
RFC 1002 March 1987
CASE error OF
NOT LISTENING ON CALLED NAME:
NOT LISTENING FOR CALLING NAME:
BEGIN
kill TCP connection;
return failure;
END
CALLED NAME NOT PRESENT:
BEGIN
/*
* called name does not exist on
* remote node
*/
inform name discovery procedure
of possible error;
IF this is a P or M node THEN
BEGIN
/*
* Inform NetBIOS Name Server
* it has returned incorrect
* information.
*/
send NAME RELEASE REQUEST for called
name and IP address to
NetBIOS Name Server;
END
/* retry from beginning */
retarget = FALSE;
name_query = TRUE;
goto LOOP;
END /* called name not present */
END /* case */
END /* negative response */
RETARGET SESSION RESPONSE:
BEGIN
close TCP connection;
extract IP address and TCP port from
response;
retarget = TRUE;
END /* retarget response */
END /* case */
LOOP: retry_count = retry_count + 1;
UNTIL (retry_count > SSN_RETRY_COUNT);
return failure;
END /* procedure */
NetBIOS Working Group [Page 70]
RFC 1002 March 1987
5.2.1.2. RECEIVED PACKET PROCESSING
These are packets received on a TCP connection before a session
has been established. The listen routines attached to a NetBIOS
user process need not implement the RETARGET response section.
The user process version, separate from a shared Session Service,
need only accept (POSITIVE SESSION RESPONSE) or reject (NEGATIVE
SESSION RESPONSE) a session request.
PROCEDURE session_packet(packet)
/*
* processing initiated by receipt of a session service
* packet for a session in the session establishment phase.
* Assumes the TCP connection has been accepted.
*/
BEGIN
CASE packet type
SESSION REQUEST:
BEGIN
IF called name does not exist on node THEN
BEGIN
send NEGATIVE SESSION RESPONSE with CALLED
NAME NOT PRESENT error code;
close TCP connection;
END
Search for a listen with CALLING NAME for CALLED
NAME;
IF matching listen is found THEN
BEGIN
IF port of listener process is port TCP
connection is on THEN
BEGIN
send POSITIVE SESSION RESPONSE;
Hand off connection to client process
and/or inform user session is
established;
END
ELSE
BEGIN
send RETARGET SESSION RESPONSE with
listener's IP address and
TCP port;
close TCP connection;
END
END
ELSE
BEGIN
/* no matching listen pending */
NetBIOS Working Group [Page 71]
RFC 1002 March 1987
send NEGATIVE SESSION RESPONSE with either
NOT LISTENING ON CALLED NAME or NOT
LISTENING FOR CALLING NAME error
code;
close TCP connection;
END
END /* session request */
END /* case */
END /* procedure */
5.2.2. SESSION DATA TRANSFER PROTOCOLS
5.2.2.1. USER REQUEST PROCESSING
PROCEDURE send_message(user_message)
BEGIN
build SESSION MESSAGE header;
send SESSION MESSAGE header;
send user_message;
reset and restart keep-alive timer;
IF send fails THEN
BEGIN
/*
* TCP connection has failed */
*/
close NetBIOS session;
inform user that session is lost;
return failure;
END
ELSE
return success;
END
5.2.2.2. RECEIVED PACKET PROCESSING
These are packets received after a session has been established.
PROCEDURE session_packet(packet)
/*
* processing initiated by receipt of a session service
* packet for a session in the data transfer phase.
*/
BEGIN
CASE packet type OF
SESSION MESSAGE:
BEGIN
process message header;
read in user data;
reset and restart keep-alive timer;
deliver data to user;
NetBIOS Working Group [Page 72]
RFC 1002 March 1987
END /* session message */
SESSION KEEP ALIVE:
discard packet;
END /* case */
END /* procedure */
5.2.2.3. PROCESSING INITIATED BY TIMER
PROCEDURE session_ka_timer()
/*
* processing initiated when session keep alive timer expires
*/
BEGIN
send SESSION KEEP ALIVE, if configured;
IF send fails THEN
BEGIN
/* remote node, or path to it, is down */
abort TCP connection;
close NetBIOS session;
inform user that session is lost;
return;
END
END /* procedure */
5.2.3. SESSION TERMINATION PROTOCOLS
5.2.3.1. USER REQUEST PROCESSING
PROCEDURE close_session()
/* initiated by a user request to close a session */
BEGIN
close gracefully the TCP connection;
WAIT for the connection to close or SSN_CLOSE_TIMEOUT
to expire;
IF time out expired THEN
abort TCP connection;
END /* procedure */
5.2.3.2. RECEPTION INDICATION PROCESSING
PROCEDURE close_indication()
/*
* initiated by a TCP indication of a close request from
* the remote connection partner.
NetBIOS Working Group [Page 73]
RFC 1002 March 1987
*/
BEGIN
close gracefully TCP connection;
close NetBIOS session;
inform user session closed by remote partner;
END /* procedure */
5.3. NetBIOS DATAGRAM SERVICE PROTOCOLS
The following are GLOBAL variables and should be NetBIOS user
configurable:
- SCOPE_ID: the non-leaf section of the domain name preceded by a
'.' which represents the domain of the NetBIOS scope for the
NetBIOS name. The following protocol description only supports
single scope operation.
- MAX_DATAGRAM_LENGTH: the maximum length of an IP datagram. The
minimal maximum length defined in for IP is 576 bytes. This
value is used when determining whether to fragment a NetBIOS
datagram. Implementations are expected to be capable of
receiving unfragmented NetBIOS datagrams up to their maximum
size.
- BROADCAST_ADDRESS: the IP address B-nodes use to send datagrams
with group name destinations and broadcast datagrams. The
default is the IP broadcast address for a single IP network.
The following are Defined Constants for the NetBIOS Datagram
Service:
- DGM_SRVC_UDP_PORT: the globally well-known UDP port allocated
where the NetBIOS Datagram Service receives UDP packets. See
section 6, "Defined Constants", for its value.
5.3.1. B NODE TRANSMISSION OF NetBIOS DATAGRAMS
PROCEDURE send_datagram(data, source, destination, broadcast)
/*
* user initiated processing on B node
*/
BEGIN
group = FALSE;
do name discovery on destination name, returns name type and
IP address;
NetBIOS Working Group [Page 74]
RFC 1002 March 1987
IF name type is group name THEN
BEGIN
group = TRUE;
END
/*
* build datagram service UDP packet;
*/
convert source and destination NetBIOS names into
half-ASCII, biased encoded name;
SOURCE_NAME = cat(source, SCOPE_ID);
SOURCE_IP = this nodes IP address;
SOURCE_PORT = DGM_SRVC_UDP_PORT;
IF NetBIOS broadcast THEN
BEGIN
DESTINATION_NAME = cat("*", SCOPE_ID)
END
ELSE
BEGIN
DESTINATION_NAME = cat(destination, SCOPE_ID)
END
MSG_TYPE = select_one_from_set
{BROADCAST, DIRECT_UNIQUE, DIRECT_GROUP}
DGM_ID = next transaction id for Datagrams;
DGM_LENGTH = length of data + length of second level encoded
source and destination names;
IF (length of the NetBIOS Datagram, including UDP and
IP headers, > MAX_DATAGRAM_LENGTH) THEN
BEGIN
/*
* fragment NetBIOS datagram into 2 UDP packets
*/
Put names into 1st UDP packet and any data that fits
after names;
Set MORE and FIRST bits in 1st UDP packet's FLAGS;
OFFSET in 1st UDP = 0;
Replicate NetBIOS Datagram header from 1st UDP packet
into 2nd UDP packet;
Put rest of data in 2nd UDP packet;
Clear MORE and FIRST bits in 2nd UDP packet's FLAGS;
OFFSET in 2nd UDP = DGM_LENGTH - number of name and
data bytes in 1st UDP;
END
BEGIN
/*
* Only need one UDP packet
*/
NetBIOS Working Group [Page 75]
RFC 1002 March 1987
USER_DATA = data;
Clear MORE bit and set FIRST bit in FLAGS;
OFFSET = 0;
END
IF (group == TRUE) OR (NetBIOS broadcast) THEN
BEGIN
send UDP packet(s) to BROADCAST_ADDRESS;
END
ELSE
BEGIN
send UDP packet(s) to IP address returned by name
discovery;
END
END /* procedure */
5.3.2. P AND M NODE TRANSMISSION OF NetBIOS DATAGRAMS
PROCEDURE send_datagram(data, source, destination, broadcast)
/*
* User initiated processing on P and M node.
*
* This processing is the same as for B nodes except for
* sending broadcast and multicast NetBIOS datagrams.
*/
BEGIN
group = FALSE;
do name discovery on destination name, returns name type
and IP address;
IF name type is group name THEN
BEGIN
group = TRUE;
END
/*
* build datagram service UDP packet;
*/
convert source and destination NetBIOS names into
half-ASCII, biased encoded name;
SOURCE_NAME = cat(source, SCOPE_ID);
SOURCE_IP = this nodes IP address;
SOURCE_PORT = DGM_SRVC_UDP_PORT;
IF NetBIOS broadcast THEN
BEGIN
DESTINATION_NAME = cat("*", SCOPE_ID)
END
ELSE
NetBIOS Working Group [Page 76]
RFC 1002 March 1987
BEGIN
DESTINATION_NAME = cat(destination, SCOPE_ID)
END
MSG_TYPE = select_one_from_set
{BROADCAST, DIRECT_UNIQUE, DIRECT_GROUP}
DGM_ID = next transaction id for Datagrams;
DGM_LENGTH = length of data + length of second level encoded
source and destination names;
IF (length of the NetBIOS Datagram, including UDP and
IP headers, > MAX_DATAGRAM_LENGTH) THEN
BEGIN
/*
* fragment NetBIOS datagram into 2 UDP packets
*/
Put names into 1st UDP packet and any data that fits
after names;
Set MORE and FIRST bits in 1st UDP packet's FLAGS;
OFFSET in 1st UDP = 0;
Replicate NetBIOS Datagram header from 1st UDP packet
into 2nd UDP packet;
Put rest of data in 2nd UDP packet;
Clear MORE and FIRST bits in 2nd UDP packet's FLAGS;
OFFSET in 2nd UDP = DGM_LENGTH - number of name and
data bytes in 1st UDP;
END
BEGIN
/*
* Only need one UDP packet
*/
USER_DATA = data;
Clear MORE bit and set FIRST bit in FLAGS;
OFFSET = 0;
END
IF (group == TRUE) OR (NetBIOS broadcast) THEN
BEGIN
/*
* Sending of following query is optional.
* Node may send datagram to NBDD immediately
* but NBDD may discard the datagram.
*/
send DATAGRAM QUERY REQUEST to NBDD;
IF response is POSITIVE QUERY RESPONSE THEN
send UDP packet(s) to NBDD Server IP address;
ELSE
BEGIN
get list of destination nodes from NBNS;
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RFC 1002 March 1987
FOR EACH node in list
BEGIN
send UDP packet(s) to this node's
IP address;
END
END
END
ELSE
BEGIN
send UDP packet(s) to IP address returned by name
discovery;
END /* procedure */
5.3.3. RECEPTION OF NetBIOS DATAGRAMS BY ALL NODES
The following algorithm discards out of order NetBIOS Datagram
fragments. An implementation which reassembles out of order
NetBIOS Datagram fragments conforms to this specification. The
fragment discard timer is initialized to the value FRAGMENT_TO.
This value should be user configurable. The default value is
given in Section 6, "Defined Constants and Variables".
PROCEDURE datagram_packet(packet)
/*
* processing initiated by datagram packet reception
* on B, P and M nodes
*/
BEGIN
/*
* if this node is a P node, ignore
* broadcast packets.
*/
IF this is a P node AND incoming packet is
a broadcast packet THEN
BEGIN
discard packet;
END
CASE packet type OF
DATAGRAM SERVICE:
BEGIN
IF FIRST bit in FLAGS is set THEN
BEGIN
IF MORE bit in FLAGS is set THEN
BEGIN
Save 1st UDP packet of the Datagram;
Set this Datagram's fragment discard
timer to FRAGMENT_TO;
NetBIOS Working Group [Page 78]
RFC 1002 March 1987
return;
END
ELSE
Datagram is composed of a single
UDP packet;
END
ELSE
BEGIN
/* Have the second fragment of a Datagram */
Search for 1st fragment by source IP address
and DGM_ID;
IF found 1st fragment THEN
Process both UDP packets;
ELSE
BEGIN
discard 2nd fragment UDP packet;
return;
END
END
IF DESTINATION_NAME is '*' THEN
BEGIN
/* NetBIOS broadcast */
deliver USER_DATA from UDP packet(s) to all
outstanding receive broadcast
datagram requests;
return;
END
ELSE
BEGIN /* non-broadcast */
/* Datagram for Unique or Group Name */
IF DESTINATION_NAME is not present in the
local name table THEN
BEGIN
/* destination not present */
build DATAGRAM ERROR packet, clear
FIRST and MORE bit, put in
this nodes IP and PORT, set
ERROR_CODE;
send DATAGRAM ERROR packet to
source IP address and port
of UDP;
discard UDP packet(s);
return;
END
ELSE
BEGIN /* good */
/*
NetBIOS Working Group [Page 79]
RFC 1002 March 1987
* Replicate received NetBIOS datagram for
* each recipient
*/
FOR EACH pending NetBIOS user's receive
datagram operation
BEGIN
IF source name of operation
matches destination name
of packet THEN
BEGIN
deliver USER_DATA from UDP
packet(s);
END
END /* for each */
return;
END /* good */
END /* non-broadcast */
END /* datagram service */
DATAGRAM ERROR:
BEGIN
/*
* name service returned incorrect information
*/
inform local name service that incorrect
information was provided;
IF this is a P or M node THEN
BEGIN
/*
* tell NetBIOS Name Server that it may
* have given incorrect information
*/
send NAME RELEASE REQUEST with name
and incorrect IP address to NetBIOS
Name Server;
END
END /* datagram error */
END /* case */
END
5.3.4. PROTOCOLS FOR THE NBDD
The key to NetBIOS Datagram forwarding service is the packet
delivered to the destination end node must have the same NetBIOS
header as if the source end node sent the packet directly to the
destination end node. Consequently, the NBDD does not reassemble
NetBIOS Datagrams. It forwards the UDP packet as is.
NetBIOS Working Group [Page 80]
RFC 1002 March 1987
PROCEDURE datagram_packet(packet)
/*
* processing initiated by a incoming datagram service
* packet on a NBDD node.
*/
BEGIN
CASE packet type OF
DATAGRAM SERVICE:
BEGIN
IF packet was sent as a directed
NetBIOS datagram THEN
BEGIN
/*
* provide group forwarding service
*
* Forward datagram to each member of the
* group. Can forward via:
* 1) get list of group members and send
* the DATAGRAM SERVICE packet unicast
* to each
* 2) use Group Multicast, if available
* 3) combination of 1) and 2)
*/
...
END
ELSE
BEGIN
/*
* provide broadcast forwarding service
*
* Forward datagram to every node in the
* NetBIOS scope. Can forward via:
* 1) get list of group members and send
* the DATAGRAM SERVICE packet unicast
* to each
* 2) use Group Multicast, if available
* 3) combination of 1) and 2)
*/
...
END
END /* datagram service */
DATAGRAM ERROR:
NetBIOS Working Group [Page 81]
RFC 1002 March 1987
BEGIN
/*
* Should never receive these because Datagrams
* forwarded have source end node IP address and
* port in NetBIOS header.
*/
send DELETE NAME REQUEST with incorrect name and
IP address to NetBIOS Name Server;
END /* datagram error */
DATAGRAM QUERY REQUEST:
BEGIN
IF can send packet to DESTINATION_NAME THEN
BEGIN
/*
* NBDD is able to relay Datagrams for
* this name
*/
send POSITIVE DATAGRAM QUERY RESPONSE to
REQUEST source IP address and UDP port
with request's DGM_ID;
END
ELSE
BEGIN
/*
* NBDD is NOT able to relay Datagrams for
* this name
*/
send NEGATIVE DATAGRAM QUERY RESPONSE to
REQUEST source IP address and UDP port
with request's DGM_ID;
END
END /* datagram query request */
END /* case */
END /* procedure */
NetBIOS Working Group [Page 82]
RFC 1002 March 1987
6. DEFINED CONSTANTS AND VARIABLES
GENERAL:
SCOPE_ID The name of the NetBIOS scope.
This is expressed as a character
string meeting the requirements of
the domain name system and without
a leading or trailing "dot".
An implementation may elect to make
this a single global value for the
node or allow it to be specified
with each separate NetBIOS name
(thus permitting cross-scope
references.)
BROADCAST_ADDRESS An IP address composed of the
nodes's network and subnetwork
numbers with all remaining bits set
to one.
I.e. "Specific subnet" broadcast
addressing according to section 2.3
of RFC 950.
BCAST_REQ_RETRY_TIMEOUT 250 milliseconds.
An adaptive timer may be used.
BCAST_REQ_RETRY_COUNT 3
UCAST_REQ_RETRY_TIMEOUT 5 seconds
An adaptive timer may be used.
UCAST_REQ_RETRY_COUNT 3
MAX_DATAGRAM_LENGTH 576 bytes (default)
NAME SERVICE:
REFRESH_TIMER Negotiated with NBNS for each name.
CONFLICT_TIMER 1 second
Implementations may chose a longer
value.
NAME_SERVICE_TCP_PORT 137 (decimal)
NetBIOS Working Group [Page 83]
RFC 1002 March 1987
NAME_SERVICE_UDP_PORT 137 (decimal)
INFINITE_TTL 0
SESSION SERVICE:
SSN_SRVC_TCP_PORT 139 (decimal)
SSN_RETRY_COUNT 4 (default)
Re-configurable by user.
SSN_CLOSE_TIMEOUT 30 seconds (default)
Re-configurable by user.
SSN_KEEP_ALIVE_TIMEOUT 60 seconds, recommended, may be set to
a higher value.
(Session keep-alives are used only
if configured.)
DATAGRAM SERVICE:
DGM_SRVC_UDP_PORT 138 (decimal)
FRAGMENT_TO 2 seconds (default)
NetBIOS Working Group [Page 84]
RFC 1002 March 1987
REFERENCES
[1] "Protocol Standard For a NetBIOS Service on a TCP/UDP
Transport: Concepts and Methods", RFC 1001, March 1987.
[2] J. Reynolds, J. Postel, "Assigned Numbers", RFC 990, November
1986.
[3] P. Mockapetris, "Domain Names - Implementation and
Specification", RFC 883, November 1983.
NetBIOS Working Group [Page 85]