User Manual - Gcom, Inc.
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1. DLPI User Manual February 2002 Protocols LAPB MLP QLLC HDLC SDLC LAPD and frame relay Copyright GCOM Inc All rights reserved 2002 GCOM Inc All rights reserved Non proprietary Provided that this notice of copyright is included this document may be copied in its entirety without alteration Permission to publish excerpts should be obtained from GCOM Inc GCOM reserves the right to revise this publication and to make changes in content without obligation on the part of GCOM to provide notification of such revision or change The information in this document is believed to be accurate and complete on the date printed on the title page No responsibility is assumed for errors that may exists in this document Rsystem is a registered trademark of GCOM Inc UNIX is a registered trademark of UNIX Systems Laboratories Inc in the U S and other countries SCO is a trademark of the Santa Cruz Operation Inc IBM PC IBM PC AT OS 2 and PC DOS are registered trademarks of International Business Machines Corporation All other brand product names mentioned herein are the trademarks or registered trademarks of their respective owners Any provision of this product and its manual to the U S Government is with Restricted Rights Use duplication or disclosure by the U S Government is subject to restrictions as set forth in subparagraph c 1 Gi of the Rights in Technical Data and Computer Software clause at 252 222. dl bind req t This structure is used to submit a bind request A bind request specifies a service access point whether or not the user will accept a DL CONNECT IND whether or not a connection oriented service is desired or whether or not the user is a connection manager dl primitive Set to DLL BIND REQ This request in valid only in the DL UNBOUND state If successful the user s state is changed to DL_IDLE dl sap DLSAP described above It specifies an address to be used when selecting a data link A DLSAP is implemented as an unstructured array of up to 7 PAGE 5 DLPI USER MANUAL PAGE 6 GCOM INC bytes A log is converted to a DLSAP by finding the high order non zero byte and copying that byte and remaining lower order bytes into the d sap Zero is a legal 41 sap and results in a 1 byte DLSAP Es Note The extended address bit bit 0 is not used to interpret the address dl_max_conind dl_service_mode dl_comm_mgmt Maximum number of DL_CONNECT_IND the user will accept A value greater than 1 implies that the user is a connection manager see dl_comm_mgmt below Connection managers are not supported and a bind request with max conind greater than 1 will be rejected A dl conind of 1 indicates the user will wait for aDL CONNECT IND When a DL CONNECT IND arrives the user can accept the connection with a DLL CONNECT RES or reject the connection with a DLL DISCONNECT REQ If the
3. Otherwise after the connection is established the user will be sent a DL CONNECT CON and placed in the DL DATAXTFER state dl primitive Set to DL CONNECT REQ dl dest length These two fields identify the peer s DLSAP dl dest addr offset If dl dest addr length is non zero the array referenced by dest addr offset and dl dest addr length must be within the user s request buffer These fields are otherwise ignored dl qos length Specifies the quality of service QOS dl qos offset parameters desired for the connection If specified the QOS parameters must be within the user s request buffer QOS is not supported and these fields are otherwise ignored dl growth A field reserved for future use that must be set to Zero PAGE 7 DLPI USER MANUAL PAGE 8 GCOM INC DL CONNECT CON This message is sent to the user when a previously requested connection see CONNECT REQ on page 7 is established The user s state is changed to DL DATAXFER typedef struct ulo ulo ulo ulo ulo ulo l dl con ng ng ng ng ng ng d dl primitive dl resp addr length di d d resp addr offset l qos length l qos offset l growth nect con t dl primitive Set to DL CONNECT CON dl resp addr length These two fields are used to return the dl resp addr offset responding DLSAP associated with the newly dl qos length dl qos offset dl growth established connect
4. is responsible for configuring the DLPI multiplexor The DLPI user has only limited capability to alter the configuration of a link that the user has bound See ioctls on page 22 User Streams files Control Stream DLPI Data Link Protocols STREAMS Interface Protocols Lower Streams identified by MUX ID Device Driver Device Driver Table 1 Streams Environment The DLPI multiplexor consists of the DLPI data link protocols and streams interface protocols The DLPI is an interface protocol giving FEBRUARY 2002 PAGE 1 DLPI USER MANUAL GCOM INC the STREAMS user access to a data link protocol The available data link protocols depending on the configuration are HDLC X 25 frame level and X 25 MLP The data link protocols do not directly access devices Instead a lower streams interface protocol is used to access a STREAMS driver which provides the device access The lower streams interface protocol must speak the streams protocol expected by the STREAMS device driver DLPI user protocol and CDI user protocol are supported User Streams Protocol Layers PAGE 2 UPA UPA DLPI Data Link Protocol UPA DLSAP DLSAP LPA muxid PPA Data Link Protocol LPA STREAMS Interface Protocol Lower STREAM Table 2 Physical Point of Attachment PPA Data Link Service Access Point DLSAP Two layers of data link protocols are supported In the GCOM UNIX Streams Admin
5. DL RESET IND to the user The user could simultaneously send a DL RESET REQ The DLPI provider would receive this request in the DL PROVIDER RESET PENDING state The DLPI State Transition Table treats this as a cannot occur transition ref 1 pages 87 90 Therefore the DLPI provider returns a DL ERROR Since the user would have received the DL RESET IND the DL ERROR ACK should be ignored and the user should proceed as ifa DL RESET REQ were never sent That is send a DL RESET RES and wait for a DL OK ACK While the connection is being reset the user may disconnect at any time or possibly receive a DLL DISCONNECT IND If the user disconnects the reset operation is aborted and a DL referencing the disconnect request is returned to the user The disconnect causes all internally queued messages to be flushed and a flush request to be sent to the streamhead That is there cannot be a previously queued DL that would cause the DL to be discarded FEBRUARY 2002 GCOM INC FEBRUARY 2002 2 USING THE DLPI PROTOCOL DL RESET REQ typedef struct ulong dl primitive dl reset req t Sent by the DLPI user to request an end to end re synchronization The user s connection must be in the DL DATAXFER state or a DL ERROR ACK is returned As described above this request can cross in the mail with a DL RESET IND or a DL DISCONNECT IND dl primitive DL RESET REQ DL RESET
6. IND typedef struct ulong dl_primitive ulong dl_originator ulong dl_reason dl_reset_ind_t Generated by the DLPI provider to report the unrecoverable loss of data or a reset request by its opposite dl_primitive DL_RESET_IND dl_originator Set to DL PROVIDER dl reason Set to DL RESET LINK ERROR The provider cannot determine what actually initiated this event PAGE 13 DLPI USER MANUAL PAGE 14 GCOM INC DL RESET RES typedef struct ulong dl primitive dl reset res t This message is sent by the DLPI user to indicate it is ready to resume a dialogue with its peer The DLPI provider responds by sending a DL OK ACK to the user and completing the reset exchange with the data link layer When the user receives the DL ACK referencing the DL RESET RES the user may begin sending data Any data received by the user after receiving the DL ACK was sent by its peer after the peer completed its reset operation dl primitive Set to DL RESET RES DL RESET CON typedef struct ulong dl primitive di reset con t This message is sent by the DLPI in response to a DLL RESET REQ It is sent after the reset operation is complete This message has the same semantics as a DL toa DL RESET RES described directly above dl primitive Set to DL RESET CON FEBRUARY 2002 GCOM INC 2 USING THE DLPI PROTOCOL Connection Release Disconnection FEBRUARY 2
7. PCPROTO STREAM s message An M PCPROTO message as stated in the STREAMs manual 1 The Stream head will allow only one M PCPROTO message to be placed in the read queue at a time If an M PCPROTO message is already in the queue when another arrives the second message is silently discarded and its message blocks freed The queue flushing that occurs during reset and disconnect operations prevents the upstream queue from filling with connect reset or disconnect protocol messages In summary the user need not be concerned about using an abnormal number of STREAMS buffers when communicating with the DLPI provider PAGE 19 DLPI USER MANUAL GCOM INC Acknowledgment Generation Acknowledgments are sent in response to user protocol messages Acknowledgments are sent to confirm that a desired action was taken DL OK ACK to report that a user request was in error DL ERROR or to return information DL INFO ACK The DLPI protocol is designed so that at most one acknowledgment is queued for delivery to the user at any given time Acknowledgments are sent in response to user protocol messages The user s state transition table definition requires that the user wait for a response ack confirm indication before proceeding This handshake protocol prevents the buildup of queued acknowledgments and is reinforced by using M PCPROTO messages to deliver these acknowledgments The DLPI provider must internally queue an acknowl
8. QOS Fields Quality of service QOS fields when provided by the user are ignored However if the user specifies a QOS field it must lie within the user s buffer QOS parameters are not generated by the DLPI provider A user generated DL UDQOS REQ is rejected with a DLL ERROR PAGE 21 XIDs TESTs ACKs NA Ks DisableResets ioctls PAGE 22 SECTION Protocol Extensions This section describes extensions to the DLPI specification supported by the DLPI provider The following extensions are optionally enabled by the network manager when a UPA is configured The exchange of XIDs and TESTs is supported while a connection is in the DL_IDLE state Any queued XIDs TESTs are flushed when the connection leaves the DL_IDLE state A protocol module can be configured to generate an ACK or NAK when a data message is acknowledged or rejected by its peer If so configured the DLPI provider will forward ACK NAKs to the user When loss of data occurs on the link the protocol module flushes any queued data and sends a reset indication to the DLPI provider The provider in turn flushes any queued data and sends a M_FLUSH and DL_RESET_IND upstream This mechanism can be disabled by the network manager when it configures a UPA The DLPI provider supports several ioctl calls on a data stream The ioctl calls can be used to change the configuration of a UPA and to obtain statistics A description of the supported ioctls can be fo
9. mentioned above There are additional events that cause a stream to be aborted These are 1 An attached LPA has been unlinked 2 The DLPI s control stream has been closed 3 Aninternal error is detected regarding buffer conversion or pointer linkage 4 A network management MN ON OFF REQ request turns off the UPA that the user has successfully bound 5 Data is received from the data link layer in an inappropriate state PAGE 18 FEBRUARY 2002 GCOM INC 2 USING THE DLPI PROTOCOL Limiting Number of STREAMS Buffers in Use FEBRUARY 2002 One of the goals of the DLPI protocol design appears to limit the number of STREAM s buffers that can be in use for any given STREAM Data delivery is flow controlled in both directions Downstream data is placed on the write queue so upstream modules or the streamhead obeying canput flow control will propagate upstream the flow control back pressure The other potential abuse of STREAM s buffers involves abusing the connection control messages such as DL BIND REQ For example if the user were in an infinite loop sending DL BIND REQs but not reading the responses it might be possible for all the STREAMS buffers to end up on the user s streamhead as DL ERROR ACKs DLPI specification writers apparently considered this possibility because acknowledgments DL INFO ACK DL BIND DL SUBS BIND ACK DL OK ACK DL ERROR ACK and DL TOKEN ACK are delivered in a M
10. user specifies a d max of 1 the user may not initiate a connection with a DLL CONNECT REQ It will be rejected A dl max conind of zero indicates that the user does not want to receive a DL CONNECT IND Instead the user can initiate a connection by sending a DL CONNECT REQ When the connection is established a DL CONNECT CON will be returned to the user Connect requests crossing in the mail are supported If the user and the user s opposite concurrently initiate a connection the connection will be established Specifies whether connection oriented DL CODLS or connectionless DL CLDLS data link service is desired Only DL CODLS is supported If non zero indicates the user is a connection manager This DLPI facility is not supported FEBRUARY 2002 GCOM INC FEBRUARY 2002 2 USING THE DLPI PROTOCOL DL CONNECT REQ typedef struct ulong dl primitive ulong dl dest addr length ulong dl dest addr offset ulong dl qos length ulong dl qos offset ulong dl growth dl connect req t A connect request is used to initiate a connection The user s stream must be in DL IDLE state The bind request must have specified a dl max conind of zero If the request is in error a DLL ERROR ACK is returned The user s state is changed to DLL OUTCON PENDING If the attempt to establish a connection fails the user is sent a DL DISCONNECT IND and returned to the DL_IDLE state
11. 002 DL DISCONNECT REQ typedef struct ulong dl_primitive ulong dl reason ulong dl correlation dl disconnect req t This request is used to disconnect an existing connection It is valid in the DL DATAXFER DL DISCON IND PENDING DL OUTCON PENDING DL INCON PENDING DL USER RESET PENDING and DL PROV RESET PENDING states The user will receive a DL ACK response when the connection is disconnected The connection is returned to the DL IDLE state It is possible for users DL DISCONNECT REQ to cross in the mail with a DL DISCONNECT IND Therefore in response to a legitimate DL DISCONNECT REQ the user can receive DL OK ACK if the DLPI provider has not received a disconnect indication from the data link layer DL DISCONNECT IND if this was queued for delivery to the user when the provider received the DL DISCONNECT REQ e DL ERROR ifaDL DISCONNECT IND has been sent to the user and the stream is now in the DL IDLE state Once the disconnect is complete the user may send another DL CONNECT REQ or wait for a DL CONNECT IND as specified in the DL BIND REQ Alternatively the user may unbind the DLSAP see below dl primitive Set to DL DISCONNECT REQ dl reason Reason the user is terminating the connection This field is 1gnored dl correlation Must be zero PAGE 15 DLPI USER MANUAL GCOM INC DL DISCONNECT IND typedef struct ulong dl primitive ulong dl ori
12. 7 7013 of the DoD FAR Supplement This manual was written formatted and produced by senior technical writer Scott D Smith using Microsoft Word 5 1 and FrameMaker 4 04 on an Apple Macintosh platform with the help of subject matter specialists Dave Healy and illustrator and publication specialist Charles Lipp This manual was printed in the U S A FOR FURTHER INFORMATION If you want more information about GCOM products contact us at GCOM Inc 1800 Woodfield Savoy IL 61874 217 351 4241 FAX 217 351 4240 e mail support gcom com homepage http gcom com GCOM INC TABLE OF CONTENTS Table of Contents D liado cds Purpose of This Guide Lo esse uM ERES Knowledge Requirements Organization of This Guide Wi Ce ese Conventions Used in This Guide MW MAA AM e A meiste is Special Notices II A Text Conventions SECTION 1 ee Lee ee ene ee ee ee ee DLPI Overview SECTION 2 uedadeuo ders orn Using the DLPI Protocol Ai ds Establishing a Connection Dro aa art lad ecd ee tare bho ine Re DL_ATTACH_REQ Dc AA As id me DL_BIND_REQ aspis yel e e act eee ae DL CONNECT REQ Si A aie lo des on tats DL CONNECT CON 9 X SLAGNM E UAM SEN rn eed DL CONNECT IND DL_CONNECT_RES Il eh ey ele es Data Transfer EM A Reset Mechanism 137 a a eder a UP abad DL RESET REQ 13 uus ac exea esed ddp a Rs DL RESET IND 14 oxid
13. A For each UPA network management may specify the DLSAP or have it defaulted appropriate to the configuration FEBRUARY 2002 PAGE 3 SECTION Using the DLPI Protocol The following discussion describes how the user establishes a connection transfers data re synchronizes a connection and releases a connection Those DLPI features not supported by the DLPI multiplexor are also described An understanding of the DLPI protocol as described in 1 will make the following discussion easier to comprehend Also discussed is the handling of fatal errors limits on the number of STREAMS buffers that can be in use for a given stream and the generation of acknowledgments Establishing a Connection PAGE 4 To establish a connection the user must first open a stream to the DLPI multiplexor ASTREAM file is similar to a character special device file The open must specify DLPI STREAMS file with a specific non zero minor device or a CLONEOPEN No additional privilege checks are performed by the DLPI multiplexor The DLPI multiplexor allows a minor device to be opened multiple times DLPI protocol messages are exchanged between the user and the DLPI provider using STREAMS control messages DLPI data messages described as DLSDUS below are exchanged in STREAMS data messages The UNIX system calls putmsg and getmsg can be used to send and receive control and data messages Write and read can also be used to send and receive data messages On
14. ES 24 dl resp addr length 18 dl resp addr offset 18 dl resp token 20 dl sap 15 dl service mode 16 31 DL STYLEI unsupported feature 31 DL STYLE2 is supported 31 DL UDQOS REQ 31 PAGE II GCOM INC DL UNATTACHED state 15 DL UNBIND REQ 26 DLPI multiplexor 11 DLPI user protocol 12 DLSAP 13 17 DLSAP disassociated from stream 26 Downstream user to data link data transfer 21 end to end re synchronization 23 enter vs type ix errors fatal 28 Establishing a Connection 14 exchange of XIDs and TESTs 32 extended address bit bit 0 16 Extended Datalink Layer Provider Interface Specification 33 extension of the DLPI 33 extensions to the DLPI specification 32 f Fatal Errors 28 features not supported for DLPI 31 forward ACK NAKs 32 8 generate an ACK or NAK 32 h handshake protocol 30 HDLC 12 indication 30 initiate a connection 17 FEBRUARY 2002 GCOM INC internal error 28 ioctls unsupported features 32 italic text conventions ix l LAPB 33 limit the number of STREAM s buffers 29 link multiplexor 12 loss of data 22 32 Lower Point of Attachment LPA 12 LPA has been unlinked 28 m ERROR 21 28 FLUSH 32 M PCPROTO 29 max sdu 21 min sdu 21 MLP 33 MN ON OFF REQ 28 n notes purpose of vili null layer 12 NULL MODULE 12 0 overview 11 p physical point of attachment PPA 12 13 15 pointer linkage 28 POLL MODULE 12 FEB
15. RUARY 2002 INDEX PPA disassociated from stream 27 Protocol Extensions 32 put procedure 30 q Quality of service QOS 17 31 unsupported feature 31 queue flushing 29 queue two or more acknowledgments 30 r reset and disconnect operations 29 Reset Mechanism 22 reset operation is complete 24 reset protocol messages 29 responses listed 30 return information 30 S screen display ix state transition table 22 30 statistics obtained 32 STREAMS Buffers in Use 29 Streams Environment 11 STREAMS based Data Link Provider Interface 33 submit a bind request 15 submit an attach request 15 Subsequent Bind Request unsupported feature 31 supported features vii t terminated the connection 26 terminology conventions 1x text conventions ix type vs enter iX PAGE III DLPI USER MANUAL unbind the DLSAP 25 UNIX Streams Administrator s Guide 33 UNIX SYSTEM V RELEASE 4 Programmer s Guide 33 unrecoverable loss of data 23 unsupported DLPI features 31 UPA configuration change 32 Upper Point of Attachment UPA 12 Upstream data link to user data transfer 21 user request was in error 30 Ww warnings purpose of viii X X 25 frame level 12 X25 12 XIDs TESTs unsupported features 32 PAGE IV GCOM INC FEBRUARY 2002
16. SDUS are delivered in order no missing no duplicates and bit error free Data delivery is flow controlled Downstream user to data link data transfer is flow controlled using the STREAM s canput flow control mechanism When the data link protocol back pressures DLPI data messages are queued on the user s STREAM s write queue until the flow control blockage is removed Upstream data link to user data transfer is similarly flow controlled canput is used to determine the amount of data that can be delivered upstream If upstream data transfer is flow control blocked the data is queued internally until the blockage is removed In addition the flow control blockage is propagated into the data link protocol module The connection must be in the DL DATAXFER state when the user transmits data Violating this restriction will result in an M ERROR being sent to the user and all user messages being discarded until the connection is closed However it s possible for the DLPI to have left the DL DATAXFER state but for the user to have not yet received any messages indicating the state had changed This can happen when a DLRESET IND ora DL DISCONNECT IND is sent to the user Therefore data messages received in the DL IDLE DL PROV RESET PENDING or DL DISCON IND PENDING state will be silently discarded by the DLPI multiplexor The DLPI specification places limits on the size of data messages the user can send to the DLPI multiplexor The
17. UPA was configured dl qos length Both these fields are null as Quality of Service dl qos offset is not supported dl growth Set to zero FEBRUARY 2002 PAGE 9 DLPI USER MANUAL PAGE 10 GCOM INC DL CONNECT RES This DLPI protocol message is sent by the user to accept a connection indication The user must be in the DL_INCON_PENDING state If the request is not in error the user s state is changed to DL DATAXFER and sent a DL ACK The user may not start sending data until the DL OK ACK is received If the user s request is in error a DL ERROR is returned typedef struct ulong ulong ulong ulong ulong ulong dl primitive dl correlation dl resp token dl qos length dl qos offset dl growth dl connect res t dl primitive dl correlation dl resp token dl qos length dl qos offset dl growth Set to DL CONNECT RES Must be zero Must be zero Specifies the quality of service QOS parameters desired for the connection If specified the QOS parameters must be within the user s request buffer QOS is not supported and these fields are otherwise ignored Must be zero FEBRUARY 2002 GCOM INC Data Transfer FEBRUARY 2002 2 USING THE DLPI PROTOCOL Data may be transferred simultaneously in both directions Data is transferred in records called data link service data units DLSDU The integrity of the DLSDU is maintained by the DLPI multiplexor DL
18. anding of ATT STREAMS 2 Some knowledge of the Network Management Interface 3 described in GCOM s UNIX Streams Administrator s Guide is useful but not required FEBRUARY 2002 PAGEI DLPI USER MANUAL GCOM INC Organization of This Guide Table 1 shows the organization of this manual and tells you where to find specific information Table 1 Location of Important Information For information about Look at Overview of the DLPI multiplexor Section 1 Using the DLPI protocol and the DLPI implementation Section 2 DLPI protocol extensions Section 3 Document references cited in earlier sections Appendix A Conventions Used in This Guide This section discusses conventions used throughout this guide Special Notices A special format indicates notes cautions and warnings The purpose of these notices is defined as follows Note Notes call attention to important features or instructions i Caution Cautions contain directions that you must follow to avoid immediate system damage or loss of data wa Warning Warnings contain directions that you must follow for your AR personal safety Follow these instructions carefully PAGE II FEBRUARY 2002 GCOM INC FEBRUARY 2002 Text Conventions PREFACE The use of italics boldface and other text conventions are explained as follows Terminology Enter vs Type Screen Display The following terms appear in boldface
19. ata transfer unsupported feature 31 conventions notes cautions and warnings viii text ix create a stack of required STREAMS drivers 13 cross in the mail 22 23 25 d data link protocol 12 Data Link Provider Access Point DLSAP 12 Data Link Provider Interface DLPI vii Data Link Service Access Point DLSAP 13 data link service data units DLSDU 21 data messages 14 Data Transfer 21 dialogue with its peer 24 DisableResets unsupported features 32 disassociate DLSAP from the stream 26 PPA from the stream 27 disconnect DLSAP from the stream 26 existing connection 25 PPA from the stream 27 disconnect protocol messages 29 DL ATTACH REQ 15 DL BIND REQ 15 31 dl called addr length 19 dl called addr offset 19 FEBRUARY 2002 DLPI USER MANUAL dl_calling_addr_length 19 dl_calling_addr_offset 19 DL_CLDLS 16 DL_CODLS 16 dl_comm_mgmt 16 dl_conn_mgmt 31 DL_CONNECT_CON 18 DL_CONNECT_IND 19 DL_CONNECT_REQ 17 DL_CONNECT_RES 20 dl_correlation 19 20 25 26 dl_dest_addr_length 17 dl_dest_addr_offset 17 DL_DETACH_REQ 27 DL_DISCONNECT_IND 25 26 DL_DISCONNECT_REQ 25 DL_ERROR_ACK 30 dl growth 17 18 19 20 DL IDLE state 17 DL INFO ACK 30 dl max conind 16 17 DL ACK 25 30 dl originator 23 26 dl ppa 15 dl primitive 15 17 18 19 20 23 24 25 26 27 dl qos length 17 18 19 20 dl qos offset 17 18 19 20 dl reason 23 25 26 DL RESET CON 24 DL RESET IND 23 32 DL RESET REQ 23 DL RESET R
20. ce a stream has been opened the user must specify a PPA and a DLSAP relative to the PPA These addresses are specified using the DLPI DL ATTACH REQ and DL BIND REQ DLPI requests Once these addresses have been established the user can request that a connection be established or wait for a connection indication This choice is indicated in a DL BIND REQ request A connection is requested using a DL CONNECT A connection indication is accepted using a DLL CONNECT RES FEBRUARY 2002 GCOM INC FEBRUARY 2002 2 USING THE DLPI PROTOCOL DL ATTACH REQ typedef struct ulong dl_primitive ulong dl_ppa dl_attach_req_t This structure is used to submit an attach request This request is valid only in the DL UNATTACHED state which is the initial state after a successful open dl_primitive Set to DL_ATTACH_REQ dl_ppa Identifies the physical point of attachment dl_ppa is set to the muxid of the I LINK d lower stream Multiple users may attach the same PPA A DL ATTACH REQ succeeds even if no data link protocol has been configured If the UPA is a multiplexor for example MLP any of its LPAs may be attached An unconfigured PPA causes either the bind request or a connect request to fail A successful attach results in the user s state being changed to UNBOUND DL BIND REQ typedef struct ulong dl primitive ulong dl sap ulong dl max conind ushort dl service mode ushort dl comm mgmt
21. directories and file names An example is the hstpar h include file Boldface names within angle brackets refer to the global copy of the file For instance lt intsx25 h gt refers to rsys include intsx25 h The following terms appear in italics variables parameters fields structures glossary terms routines functions programs utilities and applications flags commands and scripts Examples include the count variable Command Type field rteparam structure target term rsys_read routine avail flag Add Route command and gcomunld script When the word enter is used in this guide it means type something and then press the Return key Do not press Return when an instruction simply says type This typeface is used to represent displays that appear on a terminal screen Commands entered at the prompt use the same typeface only in boldface For example gt gcom gcom cd gcom Each of these commands instructs you to enter cd gcom at the system prompt PAGE III DLPI USER MANUAL GCOM INC PAGEIV FEBRUARY 2002 SECTION DLPI Overview An overview of the DLPI multiplexor architecture is presented The intent of the discussion is that the user understand addressing used to establish a DLPI connection and gain a feel for the protocol processing that occurs on a data message The DLPI is implemented as a STREAMS multiplexor A network manager using the network management interface
22. e eri RES er n heats DL RESET RES Be sut e a Son e es DL RESET CON I5 1 f stetiluMuw Connection Release Disconnection 1597 obnixe deb easi esten DL DISCONNECT REQ 162 id DL_DISCONNECT_IND DL_UNBIND_REQ utente oed eod ledere en DL DETACH REQ 8200 ER RUE E E Fatal Errors IO Limiting Number of STREAMS Buffers in Use 20 Acknowledgment Generation Den rau DLPI Features Not Supported o toe Connection Manager 2l ch dated DL STYLEI 2l ED edad Aedes Subsequent Bind Request ORT RUE Quality of Service QOS Fields SECTION 3 oe RENNES Shetty anh EPOR IN Protocol Extensions FEBRUARY 2002 PAGE 1 NPI USER MANUAL GCOM INC 225 MS Rud e apes XIDs TESTs A dude A Eus E ACKs NAKs 22 E aed DisableResets RR AR RR LIE eee ex e dE ioctls ST eee ee toad tales References INDEX i PAGE 2 FEBRUARY 2002 Pd Purpose of This Guide This implementation of the Data Link Provider Interface DLPI provides connection oriented access to several data link protocols It supports connection establishment flow controlled data transfer a re synchronization mechanism and connection teardown Knowledge Requirements The discussion in this manual assumes the reader is familiar with the DLPI protocol 1 and has some underst
23. edgment for later delivery to the user when a sufficiently large buffer is not available to carry the acknowledgment It is possible for the user to violate the DLPI protocol in such a way that the DLPI provider would have to queue two or more acknowledgments Since acknowledgments are delivered in M PCPROTO messages this situation is analogous to having a PCPROTO message arrive at the queue head while aM PCPROTO message is already queued That is the DLPI provider will silently discard an acknowledgment if another is already queued for delivery Streams modules should take care when processing an acknowledgment because the DLPI provider processes streams messages on top of its put procedure That is the user streams module is usually recursively invoked to deliver an acknowledgment The delivery is deferred if no buffer is immediately available for the ack or if a data link layer interaction is required PAGE 20 FEBRUARY 2002 GCOM INC 2 USING THE DLPI PROTOCOL DLPI Features Not Supported FEBRUARY 2002 The following DLPI protocol features are not supported Connection Manager That is in a DL BIND REQ request d conn must be set to Zero DL STYLEI1 Only DL STYLE2 is supported This is set by network management Subsequent Bind Request DL ERROR ACK is returned to a DLL SUBS BIND REQ and a DL SUBS UNBIND REQ A DL SUBS BIND ACK is not generated by the DLPI provider Quality of Service
24. ginator ulong dl reason ulong dl correlation dl disconnect ind t This message is generated by the DLPI provider and sent to the user It is used to report that the user s opposite has terminated the connection No response by the user is required the connection state is changed to DL IDLE dl primitive DL DISCONNECT IND dl originator Set to DL PROVIDER dl reason Setto DL DISC UNSPECIFIED dl correlation Set to zero DL UNBIND REQ typedef struct ulong dl primitive dl unbind req t An unbind request is used to disassociate the DLSAP from the stream This request is valid only in the DL IDLE state If successful a DL OK ACK is returned to the user and the state is changed to DL UNBOUND dl primitive DL UNBIND REQ PAGE 16 FEBRUARY 2002 GCOM INC FEBRUARY 2002 2 USING THE DLPI PROTOCOL DL DETACH REQ typedef struct ulong dl primitive dl detach req t A detach request is used to disassociate the PPA from the stream This request is valid only in the DL UNBOUND state If successful a DL OK ACK is returned to the user and the state is changed to DL UNATTACHED dl primitive DL DETACH REQ PAGE 17 DLPI USER MANUAL GCOM INC Fatal Errors The DLPI specification has the notion of a fatal error When a fatal error occurs an M ERROR is sent to the user and all messages are discarded until the user closes the stream Two such cases involving data transfer were
25. ion This is the d prm dl bind dlsap specified in a network management upper configuration request dl resp addr offset is an offset into the user s buffer indicating where the DLSAP is located dl resp addr length is the number of bytes required for the DLSAP These two fields are null because Quality of Service is not supported Zero FEBRUARY 2002 GCOM INC 2 USING THE PROTOCOL DL CONNECT IND A DL CONNECT IND is sent to the user to indicate that the user s opposite is attempting to establish a connection The user should respond with a DLL CONNECT RES to accept the connection or a DL DISCONNECT REQ to reject the connection These two user responses are described below The user s state is changed to DL INCON PENDING typedef struct ulong dl primitive ulong dl correlation ulong dl called addr length ulong dl called addr offset ulong dl calling addr length ulong dl calling addr offset ulong dl qos length ulong dl qos offset ulong dl growth dl connect ind t dl primitive Set to DLL CONNECT IND dl correlation Set to zero dl called addr length Specifies the location within the user s buffer dl called addr offset ofa DLSAP This is the DLSAP specified in the user s DL BIND request dl calling addr length Specifies the location within the user s buffer dl calling addr offset of a DLSAP This is the d peer dlsap specified when the
26. istrator s Guide these two layers are referred to as Lower Point of Attachment LPA and Upper Point of Attachment UPA In general the LPA provides possibly multiplexed access to the Physical Point of Attachment PPA ref 1 The UPA provides a data link protocol such as X 25 MLP HDLC and X 25 frame level The LPA protocol can either be a link multiplexor that is POLL MODULE or a null layer that 15 NULL MODULE For the NULL MODULE the only supported data link protocol is which provides its own device access FEBRUARY 2002 GCOM INC 1 DLPI OVERVIEW Before a user can access the DLPI multiplexor the multiplexor must be configured Network management facilities using the control stream would 1 For each device create a stack of required STREAMS drivers and I_LINK the stack under the multiplexor The multiplexor id returned in the I_LINK is used to specify the physical point of attachment PPA in a DLPI DL_ATTACH_REQ request 2 For each I_LINK d lower stream configure the access point specifying interface protocol and data link protocols This occurs in two steps First the LPA is configured specifying a streams interface protocol and an optional data link protocol Then one or more UPAs are configured A configured UPA has a data link protocol module and a logical address called Data Link Service Access Point DLSAP The DLSAP is relative to the PPA and specifies a data link provided over the PP
27. se are sdu and max du These are the minimum and maximum number of bytes that can be transmitted in a single data message These values are set when the data link is configured and can be found in a DL INFO Violating these limits results in an M ERROR being sent to the user PAGE 11 DLPI USER MANUAL Reset Mechanism PAGE 12 GCOM INC The DLPI provides a reset mechanism to report the unrecoverable loss of data and to enable users to recover from errors that cause the user to get out of sync with its peer That is the reset mechanism enables peers to restart their dialogue after such errors DLPI accomplishes this by causing the communication path between the two peers to be flushed and informing the peers when their dialogue may be resumed If the user s peer to peer protocol does not support a re synchronization event the user should probably disconnect to prevent a reception of a DL RESET IND For the re synchronization mechanism to work correctly the user s peer s interface to the link level must follow the DLPI standard If the local user initiates the reset the user should discard any data received before a DLL RESET CONFIRM is received That is depending on the STREAMS implementation it might be possible for a data message to cross in the mail with the users DL RESET REQ message Another crossing in the mail case is when the DLPI receives a reset indication from its data link protocol module and sends a
28. und in the GCOM UNIX Streams Administrator s Guide FEBRUARY 2002 APPENDIX References 1 A STREAMS based Data Link Provider Interface Version 1 2 R J Lewis J K Fellin and D J Olander AT amp T Bell Laboratories 2 UNIX TM SYSTEM V RELEASE 4 Programmer s Guide STREAMS UNIX Software Operation 1990 3 UNIX Streams Administrator s Guide GCOM 1994 4 Extended Datalink Layer Provider Interface Specification NCR Corporation Inc April 17 1990 5 Proposed extension of the DLPI for use between MLP and LAPB GCOM September 13 1990 6 CDI specification FEBRUARY 2002 PAGE 23 DLPI USER MANUAL GCOM INC PAGE 24 FEBRUARY 2002 INDEX a ack 30 Acknowledgment Generation 30 Acknowledgments 30 listed 29 ACKs NAKs unsupported features 32 action was taken 30 angle bracket conventions ix architecture 11 AT amp T Bell Laboratories 33 attach request 15 b back pressure 21 bind request submitted 15 blockage 21 boldface text conventions ix buffer abuse 29 buffer conversion 28 canput flow control mechanism 21 29 cautions purpose of viii CDI specification 33 CDI user protocol 12 change the configuration of a UPA 32 CLONEOPEN 14 closed DLPI control stream 28 confirm 30 connection establishment 14 manager unsupported feature 31 managers 16 PAGEI oriented DL CODLS 16 release 25 request initiation 17 terminated 26 connectionless DL CLDLS 16 Connectionless d
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