GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc1329

Network Working Group P. Kuehn Request for Comments: 1329 May 1992

     Thoughts on Address Resolution for Dual MAC FDDI Networks

Status of this Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard.  Distribution of this memo is
 unlimited.

1. Abstract

 In this document an idea is submitted how IP and ARP can be used on
 inhomogeneous FDDI networks (FDDI networks with single MAC and dual
 MAC stations) by introducing a new protocol layer in the protocol
 suite of the dual MAC stations.  Thus two dual MAC stations are able
 to do a load splitting across the two rings and use the double
 bandwidth of 200 Mbits/s as single MAC stations.  The new layer is an
 extension of layer 3.  For the user, the higher layer protocols, IP
 and ARP the property "dual MAC" is transparent.  No modification is
 required in the protocol suite of single MAC stations and transparent
 bridges.

2. Acknowledgements

 This paper is a result of a diploma thesis prepared at the Technical
 University of Munich, Lehrstuhl fuer Kommunikationsnetze, in co-
 operation with the Siemens Nixdorf AG.  The author would like to
 thank Jrg Eberspher and Bernhard Edmaier from the university, Andreas
 Thimmel and Jens Horstmeier from the SNI AG at Augsburg for the
 helpful comments and discussions.

3. Conventions

 Primary MAC, P-MAC           MAC, placed on the primary ring
 Secondary MAC, S-MAC         MAC, placed on the secondary ring
 Inhomogeneous ring           configuration of a dual FDDI ring with
                              single MAC and dual MAC stations
 DMARP                        Dual MAC Address Resolution Protocol

4. Assumptions

 When a dual FDDI ring wraps, both MACs in a dual MAC station are
 assumed to remain connected to the ring.  ANSI is just investigating
 whether the Configuration Management in the Station Management of a

Kuehn [Page 1] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

 FDDI station can be modified to allow this.  According to the FDDI
 SMT standard [1], different addresses are required for all MACs on
 the primary and the secondary ring.
 In this paper, the MAC in a single MAC station is assumed to reside
 on the primary ring.  The application of single MAC stations which
 have their MAC attached to the secondary ring is not precluded, but
 therefor additional connectivity between the two rings is required.
 These configurations are beyond the scope of this document.

5. The Application of Transparent Bridges

 Transparent bridges can provide links to other 802 LANs or further
 inhomogeneous FDDI rings.  The connection between two inhomogeneous
 FDDI rings can be realized by one or two transparent bridges. When
 two transparent bridges are used, one transparent bridge links the
 primary rings, the other the secondary rings.  If two secondary rings
 are connected by a transparent bridge, a path of transparent bridges
 must exist between the two primary rings.  No transparent bridges are
 allowed between the primary and the secondary ring.

6. Protocol Layers in Single MAC Stations

 The new protocol layer, named load sharing layer, is drafted to be
 introduced only in dual MAC stations.  In single MAC stations, IP and
 ARP are working on top of the Subnetwork Access Protocol (SNAP) 04]
 and the Logical Link Control protocol (802.2 LLC) [3].  LLC type 1 is
 used because connectionless services are investigated only.

Kuehn [Page 2] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

    +--------------------------+
    |   IP                     |
    +--------------------------+
    +--------------------------+
    |   ARP                    |
    +--------------------------+
     |             |
     | ARP frames  | IP frames
     |             |
    +--------------------------+
    |   SNAP                   |
    +--------------------------+
    +--------------------------+
    |   LLC                    |
    +--------------------------+
    +--------------------------++-------+
    |   FDDI-MAC               || F     |
    +--------------------------+| D  S  |
    +--------------------------+| D  M  |
    |   FDDI PHY and PMD       || I  T  |
    +--------------------------++-------+
 For the ARP layer, the following model is assumed:
 +-------------------------------------------------------X-----------+
 |  - ARP entity -                                       |           |
 |                                                       | IP frames |
 | +----------------+   +----------------+ read          |           |
 | | Cache          |   |                | entries +-------------+   |
 | | Administration |->-|  Address Cache |------>--| Address     |   |
 | +----------------+   |                |         | Conversion  |   |
 |     |                +----------------+         | Unit        |   |
 |     | ARP frames                                +-------------+   |
 |     |                                               / |           |
 |     | ___________ <- ARP requests _________________/  | IP frames |
 |     |/                                                |           |
 +-----X-------------------------------------------------X-----------+
 The Address Conversion Unit handles the actual conversion of IP
 addresses to hardware addresses.  For this purpose, it uses the
 information in the ARP cache.  The cache administration communicates
 with other ARP entities by ARP and creates, deletes and renews the
 entries in the cache.

7. Protocol Layers in Dual MAC Stations

 The load sharing layer provides the same interface to ARP as SNAP
 does.  To exchange information about addresses and reachability, the
 load sharing entities in dual MAC stations communicate with the Dual

Kuehn [Page 3] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

 MAC Address Resolution Protocol (DMARP).  For the transmission of
 DMARP frames the SNAP SAP of LLC is used, as for IP and ARP, too.
 The Organizationally Unique Identifier (OUI) in the SNAP header is
 set to zero (24 bit), the EtherType field (16 bit) contains a new
 number indicating DMARP, which is not defined yet.
 +---------------------------------------------------------+
 |                         IP                              |
 +---------------------------------------------------------+
 +---------------------------------------------------------+
 |                         ARP                             |
 +---------------------------------------------------------+
           | ARP frames                 | IP frames
 +---------------------------------------------------------+
 |                 Load Sharing Layer                      |
 +---------------------------------------------------------+
  |        |        |          |        |        |
  | ARP    | DMARP  | IP       | ARP    | DMARP  | IP
  | frames | frames | frames   | frames | frames | frames
  |        |        |          |        |        |
 +-------------------------+  +----------------------------+
 |   SNAP 1                |  |    SNAP 2                  |
 +-------------------------+  +----------------------------+
 +-------------------------+  +----------------------------+
 |   LLC 1                 |  |    LLC 2                   |
 +-------------------------+  +----------------------------+
 +-------------------------+  +----------------------------++-------+
 |   Primary MAC           |  |    Secondary MAC           || F     |
 +-------------------------+  +----------------------------+| D  S  |
 +---------------------------------------------------------+| D  M  |
 |                  FDDI PHY and PMD                       || I  T  |
 +---------------------------------------------------------++-------+

8. Running Inhomogeneous FDDI Rings

8.1. Exchange of Primary MAC Addresses between Stations

 IP and higher layer protocols only use the network independent IP
 addresses.  The ARP entity takes upon the conversion of an IP address
 to the appropriate hardware address.  To make the property dual MAC"
 transparent, ARP may only know the addresses of MACs on the primary
 ring. Therefore, the load sharing entity always delivers ARP frames
 to SNAP 1 for transmission.  By this way, communication with ARP is
 done over the primary ring in normal state.  A secondary MAC can
 receive an ARP frame when the dual ring is wrapped and the
 destination hardware address is a multicast or broadcast address.
 These frames will be discarded because they were received twice.

Kuehn [Page 4] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

 By this way, the associations of IP addresses to primary MAC
 addresses for the single MAC and dual MAC stations are stored in the
 ARP cache.  The ARP cache contains no secondary MAC addresses.

8.2. Exchange of Secondary MAC Addresses between Dual MAC Stations

 The load sharing layer needs to know the secondary MAC addresses of
 the other dual MAC stations.  The DMARP is used to get these
 addresses.  Whenever the load sharing entity delivers an ARP frame to
 SNAP 1, a DMARP reply frame will be sent on the secondary ring,
 containing the stations primary and secondary MAC address. The
 destination hardware address in this DMARP frame is the broadcast MAC
 address, the EtherType field in the SNAP header identifies DMARP.
 The IP destination address is copied from the ARP frame.  If the ARP
 frame that was transmitted parallel to the DMARP reply was a request,
 an ARP reply frame will be sent back to the sending station by the
 ARP entity in the receiving station. When the load sharing layer in
 the receiving station delivers this ARP reply frame to SNAP 1, it
 sends a DMARP reply frame on the secondary ring.
 By this way, DMARP exchanges the additionally required secondary MAC
 addresses between the dual MAC stations.  This is done parallel to
 the exchange of the ARP frames.

8.3. Communication of Dual MAC Stations on Different Dual FDDI Rings

 If two inhomogeneous dual FDDI rings are connected by one transparent
 bridge, dual MAC stations placed on different dual FDDI rings cannot
 perform a load sharing.  If both dual FDDI rings remain in normal
 state, no DMARP reply frames get from one secondary ring to the other
 secondary ring.  A dual MAC station realizes another dual MAC station
 placed on the other dual ring as a single MAC station, because it
 only receives ARP frames from it.  If one of the dual rings is
 wrapped, a DMARP reply frame can get on the primary ring of the other
 dual ring.  A target station on the unwrapped ring receives this
 DMARP frame by the primary MAC and the load sharing entity stores the
 contained addresses in an entry in the address cache.  This entry is
 marked with a control bit, named the OR-bit Other ring bit").  No
 load sharing will be done with a station related to an entry with the
 OR-bit set.
 If both dual FDDI rings are wrapped, the MACs of all stations reside
 on one ring.  Now, dual MAC stations placed on different dual rings
 can communicate with DMARP.  If a DMARP reply frame is received by
 the primary MAC and no entry exists for the sending station, a new
 entry with OR-Bit set will be created.  Otherwise, the OR-bit will be
 set in the existing entry.  If a DMARP reply frame is received by the
 secondary MAC and an entry with OR-bit set already exists for the

Kuehn [Page 5] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

 sending station, the bit will not be reset.
 This mechanism provides that no load sharing will be done between
 Dual MAC stations on different dual rings if the dual rings are
 linked with one transparent bridge.  An additional DMARP error frame
 is used to provide against errors when a DMARP reply frame gets lost
 on the ring.

8.4. Timeout of Entries Marked with OR-Bit Set

 If a FDDI ring is wrapped, the DMARP reply frames are received by the
 primary and secondary MACs of the target dual MAC stations.  In that
 case, the entries for dual MAC stations on the same dual ring are
 also marked with the OR-bit, although the load sharing is possible
 between these stations.
 When an OR-bit in an entry is set for the first time, a timer entity
 is started. If the timer entity runs out, a DMARP request frame is
 sent over SNAP 2 to the secondary MAC of the associated target)
 station.  Then the entry will be discarded.
 If the request cannot be received by the target station because the
 network configuration has changed, there is no entry in the address
 cache for this station any more and no load sharing is computed.  If
 the target station receives the DMARP request frame, it sends back a
 DMARP reply frame.

8.5. Problems with the Application of Large FDDI Networks

 With an increasing number of dual FDDI rings, each one linked
 together by two transparent bridges, the probability increases, that
 one of these inhomogeneous dual FDDI rings is wrapped in the moment
 when two dual MAC stations exchange ARP frames and DMARP replies.
 If two dual MAC stations are communicating for the first time, the
 probability decreases that a load sharing is really computed after
 the exchange of DMARP replies, although this would be possible
 according to the network configuration.  It relies upon the fact,
 that DMARP replies get to the primary ring over the wrapped dual ring
 and only entries marked with the OR-bit set are created. To solve
 this problem further expedients are invented:
 At first, entries in the address cache can be marked read-only by the
 setting of the R-bit.  In dual MAC stations, entries can be written
 manually for other dual MAC stations that are frequently talked to or
 that have a special importance.  The control bits of these entries
 cannot be changed by DMARP.

Kuehn [Page 6] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

 Next, additional control bits are introduced.  One of these bits is
 the Hold-bit (H-bit). When two dual MAC stations exchange ARP frames
 and DMARP replies to create entries in their address caches, one
 station starts sending a DMARP reply, first.  According to the
 network state, it sends an additional DMARP error frame, a moment
 later.  Within a maximum period of time (see "Configuring the Timer
 Parameters"), all frames arrive at the neighbour station and are
 received by the primary and/or secondary MAC.  If the OR-bit was not
 set for an entry within this period of time, it is clear, that no
 further DMARP frames will be received, which result in setting the
 OR-bit.  For such an entry the H-bit is set.  As the reception of
 reply and error frames is not sufficient for setting the OR-bit when
 the H-bit is set, the load sharing is assumed to be sure.  The
 correctness of the H-bit will be verified in relatively long time
 periods by queries (query and hold frames) at the station associated.
 For two communicating stations there exists a possibility to get
 information from a third station.  Always, when the OR-bit is set for
 an entry in a dual MAC station, a search frame is transmitted by the
 secondary MAC, containing the own primary MAC address and the primary
 MAC address of the counter station.  If a third station can compute a
 sure load sharing with both stations (the H-bit is set for the
 associated entries), the stations can perform a load sharing between
 them, too.  The third station informs these stations by sending found
 frames to them.

8.6. Multicast and Broadcast Addresses in IP Frames

 If the destination hardware address of an IP frame is a multicast or
 broadcast hardware address, the frame is always delivered to SNAP 1
 and sent on the primary ring, because one of the addressed stations
 could be a single MAC station.  IP frames which are delivered to the
 load sharing entity by SNAP 2 are discarded by the load sharing
 entity.  Thus, the duplication of these frames can be prevented.

9. Internal Structure

 One load Sharing entity exists in the load sharing layer.  This load
 sharing entity consists of the address cache, the cache
 administration and the multiplexer.

Kuehn [Page 7] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

 to ARP                                                     to ARP
 +----X----------------------------------------------------X--------+
 |    |                                                   | IP      |
 |    | ARP frames                            read        | frames  |
 |    |                                       entries     |         |
 | +----------------------------+   +---------+       +----------+  |
 | | Cache Administration       |->-| Address |---->--|  Multi-  |  |
 | +----------------------------|->-| Cache   |       |  plexer  |  |
 |  |        |        |        |    +---------+       |          |  |
 |  |        |        |        |                      +----------+  |
 |  | ARP    | DMARP  | ARP    | DMARP                |        |    |
 |  | frames | frames | frames | frames            IP |     IP |    |
 |  |        |        |        |               frames | frames |    |
 |  |        |        |        |                      |        |    |
 +--X--------X--------X--------X-----------------------X--------X---+
 to SNAP 1         to SNAP 2                    to SNAP 1   to SNAP 2

9.1. The Address Cache

 In the address cache, the associations of primary MAC addresses to
 secondary MAC addresses are stored for other dual MAC stations on the
 network.  There are no entries for single MAC stations.
 Because the OR- and the LS-bit (see table) always have inverted
 values, one of the bits is redundant.  Afterwards the examination of
 an entry state gets easier by the introduction of both bits, they are
 defined together.  The ARP is able to support other protocol address
 formats than the IP format.  To support this ARP property by DMARP,
 the protocol type number as used in the ARP frames is stored in every
 entry of the address cache.  So, a dual MAC station is able to
 communicate with another station with DMARP, even if the other
 station does not use IP.  The numbers used in DMARP frames and the
 address cache for the protocol type and the address length are taken
 over from ARP.
 name               length     comment
 --------------------------------------------------------------------
 P-MAC address      48 bit     Address of the primary MAC
                               in an other dual MAC station
 S-MAC address      48 bit     Address of the secondary MAC
                               in that station
 LS-bit             1 bit      A load sharing can be performed
                               with that station
                               ("Load sharing bit")

Kuehn [Page 8] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

 OR-bit             1 bit      No load sharing may be done
                               with that station
                               ("Other ring bit")
 H-bit              1 bit      The load sharing with that
                               station is trusty.
                               ("Hold bit")
 Q-bit              1 bit      A query frame was sent to that
                               station, no hold frame was
                               received yet ("Query bit")
 R-bit              1 bit      This entry cannot be changed by
                               DMARP ("Read-only bit")
 V-bit              1 bit      The entry is valid
                               ("Valid bit")
 subscript          32 bit     Unique number, identifying this
                               entry
 protocol type      16 bit     Number of the protocol type
                               that was last used in that
                               station

9.2. The Multiplexer

 The multiplexer deals with multiplexing the IP frames upon the two
 FDDI rings.  Broadcast and multicast frames are always sent on the
 primary ring.  Otherwise, the contents of the address cache and a load
 sharing criteria are used to decide on which of the rings an IP frame
 has to be transmitted.  If there is no entry for the primary MAC
 address of the destination station in the cache, the IP frame is
 transmitted on the primary ring.  If there is an entry for the
 destination station and the LS-bit is set, a load sharing can be done
 with this station.  Later on a load sharing criteria, which is beyond
 the scope of this document, decides, which one of the rings is used
 for transmission.  An example for a load sharing criteria is the
 length of the transmit queues in the MACs.  The multiplexer requires an
 abstract function only, which returns the appropriate ring for the
 transmission of an actual IP frame.
 Additionally, the multiplexer filters the received IP frames:
 multicast or broadcast frames received from the secondary MAC are
 discarded.

Kuehn [Page 9] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

9.3. The Cache Administration

 The cache administration creates and deletes the entries in the
 address cache.  For this purpose, it communicates with other load
 sharing entities in other dual MAC stations with the DMARP.  The
 cache administration handles the delivery of ARP frames to the ARP
 and the SNAP entity in the station, respectively.
 The cache administration needs three timers for the communication with
 the DMARP, which have to be supported by the system environment.  Each
 of these timers must support a timer entity for each entry in the
 address cache, whereby a single one is running at a time.
 Supported timer services:
    TIMER_request(time, name, subscript)
    TIMER_response(name, subscript)
    TIMER_cancel(name, subscript):
 A timer entity is started by the service TIMER_request and cancelled
 by the TIMER_cancel service request. The TIMER_response service
 indicates that a timer entity has run out.  The parameter name is the
 name of a timer: OR-Entry-Timer, Hold-Timer, or Query-Timer.  Each
 entry in the address cache is uniquely identified by a number
 subscript).  This number is also the number of an associated timer
 entity.  How to dispose these numbers is a question of
 implementation.  The parameter time determines the time period when
 the timer runs out.  This parameter has the value OR-set-timeout for
 the OR-Entry-Timer, Hold-time for the Hold-Timer and Query-time for
 the Query-Timer.

9.4. Configuring the Timer Parameters

 The OR-set-timeout parameter for the OR-Entry-Timer
    The period of time, determined by this parameter, should be
    essentially longer than the maximum time for a frame to travel
    around the entire network.  The expression entire network means
    the network which is constituted by the subnetworks linked
    together with transparent bridges.  When entries with OR-bit set
    are created continuously for a dual MAC station by the timeout
    mechanism, this parameter determines the periods of time between
    the consecutive requests that are sent to this station.  If the
    state of the dual FDDI ring changes and an entry with LS-bit set
    could be created, this parameter additionally determines the
    maximum time until the new entry is created.  (If an entry could
    not be created by transmission of search frames.)  Therefore, the
    OR-set-timeout parameter should be set to some 10 seconds.

Kuehn [Page 10] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

 The Hold-time parameter for the Hold-Timer
    The period of time, determined by this parameter, should as well
    be essentially longer than the maximum time for a frame to travel
    around the entire network.  When two stations communicate for the
    first time, they exchange ARP frames and DMARP replies.  The
    Hold-time parameter determines the period of time until the load
    sharing is assumed to be accomplished after the setting of the
    LS-bit.  In this period of time, the frames mentioned above must
    have reached its destination.  If an entry would be marked with
    the H-bit incorrectly, the time until it gets corrected will be
    relatively long (Query time).  Proposed dimension: several
    minutes.
 The Query-time parameter for the Query-Timer
    When an entry is marked with LS- and H-bit it is assumed, that
    load sharing can be performed with the associated station.  To
    allow the correction of a wrong value of the H-bit, the
    correctness of the H-bit is tested in periods of time, determined
    by the parameter Query-time.  It is tested whether a frame is
    received, which was sent by the secondary MAC to the secondary MAC
    address of the target station.  (The target station acknowledges
    the reception of the query frame by a hold frame.)  To limit the
    traffic caused by the query and hold frames, the parameter Query-
    time should be set to several minutes.

9.5. Format of DMARP Frames

 fieldname            length            comment
 --------------------------------------------------------------------
 hardware type        16 bit            1 = "ethernet"
 protocol type        16 bit            2048D = "Internet
                                        Protocol"
 length of hardware   8 bit             Value in octets,
 addresses                              6 for 48 bit MAC addresses
 length of protocol   8 bit             Value in octets,
 addresses                              4 for Internet addresses
 operation            16 bit            1: "reply"
                                        2: "request"
                                        3: "error"
                                        4: "search"
                                        5: "found"

Kuehn [Page 11] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

                                        6: "query"
                                        7: "hold"
 1. hardware address  ... octets
 2. hardware address  ... octets
 protocol address     ... octets
 sender
 protocol address     ... octets
 receiver
  1. ——————————————————————-
 The value for the field "protocol type" is the same as in ARP frames.

9.6. Contents of DMARP Frames

 In the following tables of DMARP frames, the fields containing the
 length and type of protocol and hardware addresses are omitted.
 Format:
 +-------------------------------------------------------------+
 | Operation | 1. hardware | 2. hardware | protocol | protocol |
 |           | address     |    address  | address  | address  |
 |           |             |             | sender   | receiver |
 +-------------------------------------------------------------+
 Operation = 1 (reply), 2 (request), 3 (error):
 +-----------------------------------------------------------------+
 | Operation | P-MAC address | S-MAC address | protocol | protocol |
 |           | sender        | sender        | address  | address  |
 |           |               |               | sender   | receiver |
 +-----------------------------------------------------------------+
 +-------------------------------------------------------------------+
 | Operation=4 | P-MAC        | P-MAC address | protocol | broadcast |
 | (search)    | address      | counter-      | address  | protocol  |
 |             | sender       | station       | sender   | address   |
 +-------------------------------------------------------------------+
 +-------------------------------------------------------------------+
 | Operation=5 | P-MAC        | S-MAC address | protocol | broadcast |
 | (found)     | address      | counter-      | address  | protocol  |
 |             | sender       | station       | sender   | address   |
 +-------------------------------------------------------------------+

Kuehn [Page 12] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

 +-------------------------------------------------------------------+
 | Operation=6 | S-MAC        | P-MAC address | protocol | broadcast |
 | (query)     | address      | counter-      | address  | protocol  |
 |             | sender       | station       | sender   | address   |
 +-------------------------------------------------------------------+
 +-------------------------------------------------------------------+
 | Operation=7 | P-MAC address | S-MAC address | protocol | protocol |
 | (hold)      | sender        | sender        | address  | address  |
 |             |               |               | sender   | receiver |
 +-------------------------------------------------------------------+
 Apart from the error frames all frames are sent on the secondary
 ring.  The reply, error and search frames are addressed to the
 broadcast hardware address.  The request, found, query and hold
 frames are addressed to an individual secondary MAC address.

10. Formal Description

 The following description is written in ESTELLE.

10.1. Global Constants, Variables and Types

default individual queue;

timescale …;

type

PDU_type = … ; (* format of a Protocol Data Unit:

                           String of variable length               *)

HW_addr_type = … ; (* format of a 48 bit MAC address *) PR_addr_type = … ; (* General: format of a protocol address

                          in an ARP or DMARP frame                 *)

IP_addr_type = … ; (* General: format of an IP address *) QoS_type = … ; (* General: format of a Quality-of-

  1. Service statement *)

timer_name_type = … ; (* Type for the name of a system timer *)

flag = (reset,set);

var

(*

The values of these variables are set in the initialization part or
by external management functions.

*)

Kuehn [Page 13] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

My_P_MAC_addr : HW_addr_type; (* Address of the MAC, placed on

                                    the primary ring               *)

My_S_MAC_addr : HW_addr_type; (* Address of the MAC, placed on

                                    the secondary ring             *)

My_IP_address : IP_addr_type; (* IP address of this station *) Broadcast_HW_addr : HW_addr_type; (* Broadcast MAC address (48 bit) *) Broadcast_IP_addr : IP_addr_type; (* Broadcast IP address *) dmarp_QoS : QoS_type; (* Quality_of_Service-statement

                                    for DMARP frames               *)

ethernet : integer; (* Type statement in DMARP frames *) ip : integer; (* Number for IP as protocol type *) fddi_addr_length : integer; (* Length of a MAC address in octetts *) ip_addr_length : integer; (* Length of a IP address in octetts *)

OR_set_timeout : integer; (* Parameter for the OR-Entry-Timer *) Query_time : integer; (* Parameter for the Hold-Timer *) Hold_time : integer; (* Parameter for the Query-Timer *)

10.2. Channels

 channel SAPchn(User,Provider);
 by User :
  UNITDATA_request
  (
    Source_addr  : HW_addr_type;
    Dest_addr    : HW_addr_type;
    QoS          : QoS_type;
    PDU          : PDU_type;
  )
 by Provider :
  UNITDATA_indication
  (
    Source_addr  : HW_addr_type;
    Dest_addr    : HW_addr_type;
    QoS          : QoS_type;
    PDU          : PDU_type;
  )
 channel System_Access_Point_chn(User,Provider);
 by User:
  TIMER_request(Time       : integer;
                Timer_id   : timer_name_type;
                subscript  : integer);
  TIMER_cancel(Timer_id    : timer_name_type;
               subscript   : integer);

Kuehn [Page 14] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

 by Provider:
  TIMER_response(Timer_id  : timer_name_type;
                 subscript : integer);

10.3. The Module Header and Interaction Points

 module LS_module systemprocess;
  ip LS_ARPSAP     : SAPchn(Provider);
     LS_IPSAP      : SAPchn(Provider);
     SNAP1_ARPSAP  : SAPchn(User);
     SNAP1_LSSAP   : SAPchn(User);
     SNAP1_IPSAP   : SAPchn(User);
     SNAP2_ARPSAP  : SAPchn(User);
     SNAP2_LSSAP   : SAPchn(User);
     SNAP2_IPSAP   : SAPchn(User);
     LS_System_Access_Point : System_Access_Point_chn(User);
 end;

10.4. The Modulebody of the Load Sharing Entity

 body LS_body for LS_module;
 module multiplexer_module process;
  ip LS_IPSAP    : SAPchn(Provider);
     SNAP1_IPSAP : SAPchn(User);
     SNAP2_IPSAP : SAPchn(User);
 end;
 module cache_administration_module process;
  ip LS_ARPSAP    : SAPchn(Provider);
     SNAP1_ARPSAP : SAPchn(User);
     SNAP1_LSSAP  : SAPchn(User);
     SNAP2_ARPSAP : SAPchn(User);
     SNAP2_LSSAP  : SAPchn(User);
     LS_System_Access_Point : System_Access_Point_chn(User);
 end;
 body cache_administration_body for cache_administration_module;
   (* defined later *)
 end;
 body multiplexer_body for multiplexer_module;
   (* defined later *)
 end;
 modvar
  cache_administration : cache_administration_module;

Kuehn [Page 15] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

  multiplexer          : multiplexer_module;
 initialize
 begin
  ethernet         := 1;
  ip               := 2048;
  fddi_addr_length := 6;
  ip_addr_length   := 4;
  init cache_administration      with cache_administration_body;
  init multiplexer               with multiplexer_body;
  attach LS_IPSAP                to multiplexer.LS_IPSAP;
  attach SNAP1_IPSAP             to multiplexer.SNAP1_IPSAP;
  attach SNAP2_IPSAP             to multiplexer.SNAP2_IPSAP;
  attach LS_ARPSAP               to cache_administration.LS_ARPSAP;
  attach SNAP1_ARPSAP            to cache_administration.SNAP1_ARPSAP;
  attach SNAP1_LSSAP             to cache_administration.SNAP1_LSSAP;
  attach SNAP2_ARPSAP            to cache_administration.SNAP2_ARPSAP;
  attach SNAP2_LSSAP             to cache_administration.SNAP2_LSSAP;
  attach LS_System_Access_Point  to cache_administration.
                                     LS_System_Access_Point;
 end; end;

10.5. The Modulebody for the Multiplexer

body multiplexer_body for multiplexer_module;

type

Type_of_addr_type = (individual, multi, broad);
ring_type         = (primary, secondary);

var

act_S_MAC_addr : HW_addr_type;

function determ_addrtype(HW_addr: HW_addr_type): Type_of_addr_type; primitive; (*

Returns the type of a hardware address.
(Individual, multicast or broadcast address)

*)

function get_cacheentry(prtype: integer; P_MAC_addr: HW_addr_type; var S_MAC_addr : HW_addr_type): boolean; primitive; (* Returns the associated secondary MAC address for a given primary MAC address and protocol type. If an entry exists, the value TRUE is returned. *)

Kuehn [Page 16] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

function ls_criteria : ring_type; (* Returns the ring on which the actual frame should be transmitted. *) primitive;

trans

when LS_IPSAP.UNITDATA_request(Source_addr,Dest_addr,QoS,PDU) begin if determ_addrtype(Dest_addr) <> individual then output SNAP1_IPSAP.UNITDATA_request(Source_addr,Dest_addr,QoS,PDU); else begin

if get_cacheentry(ip,Dest_addr,act_S_MAC_addr) and
 (ls_criteria=secondary) then
output SNAP2_IPSAP.UNITDATA_request(My_S_MAC_addr,
 act_S_MAC_addr,QoS,PDU);
else
output SNAP1_IPSAP.UNITDATA_request(Source_addr,Dest_addr,QoS,PDU);

end; end;

when SNAP1_IPSAP.UNITDATA_indication(Source_addr,Dest_addr,QoS,PDU) begin output LS_IPSAP.UNITDATA_indication(Source_addr,Dest_addr,QoS,PDU); end;

when SNAP2_IPSAP.UNITDATA_indication(Source_addr,Dest_addr,QoS,PDU) begin if determ_addrtype(Dest_addr) = individual then begin

Dest_addr := My_P_MAC_addr;
output LS_IPSAP.UNITDATA_indication(Source_addr,Dest_addr,QoS,PDU);

end; end;

10.6. The Modulebody for the Cache Administration

body cache_administration_body for cache_administration_module;

type arp_pdu_type = record

hwtype        : integer;
prtype        : integer;
HW_length     : integer;
PR_length     : integer;
operation     : (request,reply);
HW_sender     : HW_addr_type;
PR_sender     : PR_addr_type;
HW_receiver   : HW_addr_type;

Kuehn [Page 17] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

PR_receiver   : PR_addr_type;

end;

dmarp_operation_type = (request,reply,error,search,found,query,hold);

dmarp_pdu_type = record

hwtype        : integer;
prtype        : integer;
HW_length     : integer;
PR_length     : integer;
operation     : dmarpoperation_type;
HW_1          : HW_addr_type;
HW_2          : HW_addr_type;
PR_sender     : PR_addr_type;
PR_receiver   : PR_addr_type;

end;

var arp_pdu : arp_pdu_type; dmarp_pdu : dmarp_pdu_type; send_pdu : dmarp_pdu_type; act_P_MAC_addr : HW_addr_type;

function my_pr_address(prtype : integer ; praddr : PR_addr_type): boolean; (* Returns TRUE, if praddr is my station address, the protocol type is prtype. (2048d for the Internet protocol) *) primitive;

function get_my_pr_addr(prtype : integer) : PR_addr_type; (* Returns my station address, the protocol has the number prtype. *)

function extract_arp_pdu(PDU : PDU_type) : arp_pdu_type; (* Returns the data contained in an ARP PDU as a record. *) primitive;

function extract_dmarp_pdu(PDU : PDU_type) : dmarp_pdu_type; (* Returns the data contained in an DMARP PDU as a record. *) primitive;

Kuehn [Page 18] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

function assemble_dmarp_pdu(dmarp_pdu : dmarp_pdu_type): PDU; (* Returns a DMARP PDU from the data in the record. *) primitive;

procedure create_entry(prtype: integer; P_MAC_addr: HW_addr_type; S_MAC_addr: HW_addr_type; LS_Bit: flag; OR_Bit: flag; H_Bit: flag; Q_Bit: flag; R_Bit: flag; V_Bit: flag); (* Creates a new entry in the address cache, if no entry with the given primary MAC address or R-bit set to one exists. The protocol type has the number prtype. The control bits are set as given in the parameters, the LS-bit is set last. *) primitive;

function search_entry(prtype : integer; P_MAC_addr : HW_addr_type): boolean; (* Returns TRUE if an entry with the primary MAC address P_MAC_addr and the given protocol type was found in the address cache. *) primitive;

procedure update_entry(prtype: integer; P_MAC_addr: HW_addr_type; S_MAC_addr: HW_addr_type); (* Searches an entry with the given primary MAC address P_MAC_address and updates the secondary MAC address in the entry if the R-bit is set to zero. *) primitive;

procedure reset_LS_bit(prtype: integer; P_MAC_addr : HW_addr_type); (* Searches an entry with the given primary MAC address P_MAC_address and resets the LS-bit if the R-bit is reset. *) primitive;

procedure set_Q_bit(prtype: integer; P_MAC_addr : HW_addr_type); (* Searches an entry with the given primary MAC address P_MAC_address and sets the Q-bit if the R-bit is reset. *) primitive;

Kuehn [Page 19] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

function H_bit_set(prtype: integer; P_MAC_addr : HW_addr_type): boolean; (* Returns TRUE if an entry exists with H-bit set to one and the given P-MAC address. *) primitive;

function OR_bit_set(prtype: integer; P_MAC_addr : HW_addr_type): boolean; (* Returns TRUE if an entry exists with OR-bit set to one and the given P-MAC address. *) primitive;

function LS_bit_set(prtype: integer; P_MAC_addr : HW_addr_type): boolean; (* Returns TRUE if an entry exists with LS-bit set to one and the given P-MAC address. *) primitive;

function Q_bit_set(prtype: integer; P_MAC_addr : HW_addr_type): boolean; (* Returns TRUE if an entry exists with Q-bit set to one and the given P-MAC address. *) primitive;

function get_subscript(prtype: integer; P_MAC_addr : HW_addr_type): integer; (* Returns the subscipt number of an entry with the given primary MAC address. *) primitive;

function get_broadcast_addr(prtype : integer): PR_addr_type; (* Returns the broadcast protocol address for the given protocol type. *)

function get_P_MAC_addr(subscript : integer) : HW_addr_type; (* Returns the primary MAC address of the entry with the given subscript

Kuehn [Page 20] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

number. *) primitive;

function get_S_MAC_addr(prtype: integer; P_MAC_addr: HW_addr_type): HW_addr_type; (* Returns the secondary MAC address of the station with the given primary MAC address. *) primitive;

procedure delete_entry(subscript : integer); (* Deletes the entry with the given subscript number if the R-bit is reset. *) primitive;

function get_pr_type(subscript : integer) : integer; (* Returns the protocol type for the entry with the given subscript number. *) primitive;

function get_pr_length(prtype : integer) : integer; (* Returns the length of a protocol address. *) primitive;

trans

when LS_ARPSAP.UNITDATA_request(Source_addr,Dest_addr,QoS,PDU) begin arp_pdu := extract_arp_pdu(PDU); output SNAP1_ARPSAP.UNITDATA_request(Source_addr,Dest_addr,QoS,PDU); dmarp_pdu.hwtype := ethernet; dmarp_pdu.prtype := arp_pdu.prtype; dmarp_pdu.HW_length := fddi_addr_length; dmarp_pdu.PR_length := arp_pdu.PR_length; dmarp_pdu.operation := reply; dmarp_pdu.HW_1 := My_P_MAC_addr; dmarp_pdu.HW_2 := My_S_MAC_addr; dmarp_pdu.PR_sender := arp_pdu.PR_sender; dmarp_pdu.PR_receiver := arp_pdu.PR_receiver;

Kuehn [Page 21] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

PDU := assemble_dmarp_pdu(dmarp_pdu); output SNAP2_LSSAP.UNITDATA_request(My_S_MAC_addr,Broadcast_HW_addr,

dmarp_QoS,PDU);

end;

when SNAP1_ARPSAP.UNITDATA_indication(Source_addr,Dest_addr,QoS,PDU) begin output LS_ARPSAP.UNITDATA_indication(Source_addr,Dest_addr,QoS,PDU); end;

when SNAP2_ARPSAP.UNITDATA_indication(Source_addr,Dest_addr,QoS,PDU) begin end;

when SNAP1_LSSAP.UNITDATA_indication(Source_addr,Dest_addr,QoS,PDU) begin dmarp_pdu := extract_dmarp_pdu(PDU); if 1) then begin

if my_pr_address(dmarp_pdu.prtype,dmarp_pdu.PR_receiver) then begin
 if not H_bit_set(dmarp_pdu.prtype,dmarp_pdu.HW_1) then begin
  if not OR_bit_set(dmarp_pdu.prtype,dmarp_pdu.HW_1) then begin
   if LS_bit_set(dmarp_pdu.prtype,dmarp_pdu.HW_1) then begin
    output LS_System_Access_point.TIMER_cancel(
     "Hold_Timer",get_subscript(dmarp_pdu.prtype,dmarp_pdu.HW_1));
    create_entry(dmarp_pdu.prtype,dmarp_pdu.HW_1,dmarp_pdu.HW_2,
     reset,set,reset,reset,reset,set);
   end;
   output LS_System_Access_point.TIMER_request(
    OR_set_timeout,"OR_Entry_Timer",
    get_subscript(dmarp_pdu.prtype,dmarp_pdu.HW_1));
   send_pdu.hwtype    := ethernet;
   send_pdu.prtype    := dmarp_pdu.prtype;
   send_pdu.HW_length := fddi_addr_length;
   send_pdu.PR_length := dmarp_pdu.PR_length;
   send_pdu.operation := search;
   send_pdu.HW_1      := My_P_MAC_addr;
   send_pdu.HW_2      := dmarp_pdu.HW_1;
   send_pdu.PR_sender := get_my_pr_addr(dmarp_pdu.prtype);
   send_pdu.PR_receiver := get_broadcast_addr(dmarp_pdu.prtype);
   PDU := assemble_dmarp_pdu(dmarp_pdu);
   output SNAP2_LSSAP.UNITDATA_request(
    My_S_MAC_addr,Broadcast_HW_addr,dmarp_QoS,PDU);
  end else begin
   if dmarp_pdu.operation=error then
   update_entry(dmarp_pdu.prtype,dmarp_pdu.HW_1,dmarp_pdu.HW_2);
  end;
 end else begin

Kuehn [Page 22] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

  if dmarp_pdu.operation = error then
  update_entry(dmarp_pdu.prtype,dmarp_pdu.HW_1,dmarp_pdu.HW_2);
 end;
end else begin
 if my_pr_address(dmarp_pdu.prtype,dmarp_pdu.PR_sender) and
  (dmarp_pdu.operation = reply) then begin
  dmarp_pdu.operation := error;
  PDU := assemble_dmarp_pdu(dmarp_pdu);
  output SNAP1_LSSAP.UNITDATA_request(
   My_P_MAC_addr,Broadcast_HW_addr,dmarp_QoS,PDU);
 end else begin
  if dmarp_pdu.operation=error and
   search_entry(dmarp_pdu.prtype,dmarp_pdu.HW_1) then
  update_entry(dmarp_pdu.prtype,dmarp_pdu.HW_1,dmarp_pdu.HW_2);

end; end; end; end;

when SNAP2_LSSAP.UNITDATA_indication(Source_addr,Dest_addr,QoS,PDU) begin dmarp_pdu := extract_dmarp_pdu(PDU); if (dmarp_pdu.operation = found) and

my_pr_address(dmarp_pdu.prtype,dmarp_pdu.PR_receiver) then begin
if not H_bit_set(dmarp_pdu.prtype,dmarp_pdu.HW_1) then begin
 if OR_bit_set(dmarp_pdu.prtype,dmarp_pdu.HW_1) then begin
  output LS_System_Access_Point.
   TIMER_cancel("OR_Entry_Timer",
   get_subscript(dmarp_pdu.prtype,dmarp_pdu.HW_1));
 end;
 if LS_bit_set(dmarp_pdu.prtype,dmarp_pdu.HW_1) then begin
  output LS_System_Access_Point.
   TIMER_cancel("Hold_Timer",
   get_subscript(dmarp_pdu.prtype,dmarp_pdu.HW_1));
 end;
 create_entry(dmarp_pdu.prtype,dmarp_pdu.HW_1,dmarp_pdu.HW_2,
  set,reset,set,reset,reset,set);
 output LS_System_Access_Point.TIMER_request(Query_time,"Query_Timer",
  get_subscript(dmarp_pdu.prtype,dmarp_pdu.HW_1));
end;

end else begin

if (dmarp_pdu.operation = reply) or
 (dmarp_pdu.operation = request) then begin
 if search_entry(dmarp_pdu.prtype,dmarp_pdu.HW_1) then
  update_entry(dmarp_pdu.prtype,dmarp_pdu.HW_1,dmarp_pdu.HW_2);
end;
if (dmarp_pdu.operation=request) and
 my_pr_address(dmarp_pdu.prtype,dmarp_pdu.PR_receiver) then begin
 send_pdu.hwtype      := dmarp_pdu.hwtype;
 send_pdu.prtype      := dmarp_pdu.prtype;

Kuehn [Page 23] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

 send_pdu.HW_length   := fddi_addr_length;
 send_pdu.PR_length   := dmarp_pdu.PR_length;
 send_pdu.operation   := reply;
 send_pdu.HW_1        := My_P_MAC_addr;
 send_pdu.HW_2        := My_S_MAC_addr;
 send_pdu.PR_sender   := get_my_pr_addr(dmarp_pdu.prtype);
 send_pdu.PR_receiver := dmarp_pdu.PR_sender;
 PDU := assemble_dmarp_pdu(dmarp_pdu);
 output SNAP2_LSSAP.UNITDATA_request(
  My_S_MAC_addr,Broadcast_HW_addr,dmarp_QoS,PDU);
end else begin
 if my_pr_address(dmarp_pdu.prtype,dmarp_pdu.pr_receiver) then begin
  case dmarp_pdu.operation of
   reply: begin
    if not ( OR_bit_set(dmarp_pdu.prtype,dmarp_pdu.HW_1) or
     LS_bit_set(dmarp_pdu.prtype,dmarp_pdu.HW_1) )then begin
     create_entry(dmarp_pdu.prtype,dmarp_pdu.HW_1,dmarp_pdu.HW_2,
      set,reset,reset,reset,reset,set);
     output LS_System_Access_Point.TIMER_request(Hold_time,
      "Hold_Timer",get_subscript(dmarp_pdu.prtype,dmarp_pdu.HW_1));
    end;
   end;
   error: begin
    if not ( OR_bit_set(dmarp_pdu.prtype,dmarp_pdu.HW_1) or
     H_bit_set(dmarp_pdu.prtype,dmarp_pdu.HW_1) ) then begin
     if LS_bit_set(dmarp_pdu.prtype,dmarp_pdu.HW_1) then
     output LS_System_access_point.TIMER_cancel(
      "Hold_Timer",get_subscript(dmarp_pdu.prtype,dmarp_pdu.HW_1));
     create_entry(dmarp_pdu.prtype,dmarp_pdu.HW_1,dmarp_pdu.HW_2,
      reset,set,reset,reset,reset,set);
     output LS_System_access_point.TIMER_request(
      OR_set_timeout,"OR_Entry_Timer",
      get_subscript(dmarp_pdu.prtype,dmarp_pdu.HW_1));
     send_pdu.hwtype          := ethernet;
     send_pdu.prtype          := dmarp_pdu.prtype;
     send_pdu.HW_length       := fddi_addr_length;
     send_pdu.PR_length       := dmarp_pdu.PR_length;
     send_pdu.operation       := search;
     send_pdu.HW_1            := My_P_MAC_addr;
     send_pdu.HW_2            := dmarp_pdu.HW_1;
     send_pdu.PR_sender       := get_my_pr_addr(dmarp_pdu.prtype);
     send_pdu.PR_receiver     := get_broadcast_addr(dmarp_pdu.prtype);
     PDU := assemble_dmarp_pdu(dmarp_pdu);
     output SNAP2_LSSAP.UNITDATA_request(
      My_S_MAC_addr,Broadcast_HW_addr,dmarp_QoS,PDU);
    end;
   end;

Kuehn [Page 24] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

   search: begin
    if not (dmarp_pdu.HW_1=My_P_MAC_addr or
     dmarp_pdu.HW_2=My_P_MAC_addr) then begin
     if H_bit_set(dmarp_pdu.prtype,dmarp_pdu.HW_1) and
      H_bit_set(dmarp_pdu.prtype,dmarp_pdu.HW_2) then begin
      send_pdu.hwtype      := ethernet;
      send_pdu.prtype      := dmarp_pdu.prtype;
      send_pdu.HW_length   := fddi_addr_length;
      send_pdu.PR_length   := dmarp_pdu.PR_length;
      send_pdu.operation   := found;
      send_pdu.HW_1        := dmarp_pdu.HW_2;
      send_pdu.HW_2        := get_S_MAC_addr(dmarp_pdu.prtype,
                               dmarp_pdu.HW_2);
      send_pdu.PR_sender   := get_my_pr_addr(dmarp_pdu.prtype);
      send_pdu.PR_receiver := get_broadcast_addr(dmarp_pdu.prtype);
      PDU := assemble_dmarp_pdu(send_pdu);
      output SNAP2_LSSAP.UNITDATA_request(My_S_MAC_addr,
       get_S_MAC_addr(dmarp_pdu.prtype,dmarp_pdu.HW_1),dmarp_QoS,PDU);
      send_pdu.HW_1 := dmarp_pdu.HW_1;
      send_pdu.HW_2 := get_S_MAC_addr(dmarp_pdu.prtype,
       dmarp_pdu.HW_1);
      PDU := assemble_dmarp_pdu(send_pdu);
      output SNAP2_LSSAP.UNITDATA_request(My_S_MAC_addr,
       get_S_MAC_addr(dmarp_pdu.prtype,dmarp_pdu.HW_2),dmarp_QoS,PDU);
     end;
    end;
   end;
   Query: begin
    if dmarp_pdu.HW_2 = My_P_MAC_addr then begin
     send_pdu.hwtype          := ethernet;
     send_pdu.prtype          := dmarp_pdu.prtype;
     send_pdu.HW_length       := dmarp_pdu.HW_length;
     send_pdu.PR_length       := dmarp_pdu.PR_length;
     send_pdu.operation       := hold;
     send_pdu.HW_1            := My_P_MAC_addr;
     send_pdu.HW_2            := My_S_MAC_addr;
     send_pdu.PR_sender       := get_my_pr_addr(dmarp_pdu.prtype);
     send_pdu.PR_receiver     := dmarp_pdu.PR_sender;
     PDU := assemble_dmarp_pdu(send_pdu);
     output SNAP2_LSSAP.UNITDATA_request(
      My_S_MAC_addr,dmarp_pdu.HW_1,dmarp_QoS,PDU);
    end;
   end;
   Hold: begin
    if H_bit_set(dmarp_pdu.prtype,dmarp_pdu.HW_1) then
    reset_Q_bit(dmarp_pdu.prtype,dmarp_pdu.HW_1);

Kuehn [Page 25] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

   end;
  end;
 end;
end;

end; end;

when LS_System_Access_Point.TIMER_response(Timer_name,subscript) begin case Timer_name of "OR_Entry_Timer": begin

act_P_MAC_addr := get_P_MAC_addr(subscript);
if OR_bit_set(get_pr_type(subscript),act_P_MAC_addr) then begin
 send_pdu.hwtype      := ethernet;
 send_pdu.prtype      := get_pr_type(subscript);
 send_pdu.HW_length   := fddi_addr_length;
 send_pdu.PR_length   := get_pr_length(send_pdu.prtype);
 send_pdu.operation   := request;
 send_pdu.HW_1        := My_P_MAC_addr;
 send_pdu.HW_2        := My_S_MAC_addr;
 send_pdu.PR_sender   := get_my_pr_addr(send_pdu.prtype);
 send_pdu.PR_receiver := get_broadcast_addr(send_pdu.prtype);
 PDU := assemble_dmarp_pdu(send_pdu);
 output SNAP2_LSSAP.UNITDATA_request(
  My_S_MAC_addr,get_S_MAC_addr(send_pdu.prtype,act_P_MAC_addr),
  dmarp_QoS,PDU);
 delete_entry(subscript);
end;

end; "Hold_Timer": begin

act_P_MAC_addr := get_P_MAC_addr(subscript);
if (not H_bit_set(get_pr_type(subscript),act_P_MAC_addr)) and
 LS_bit_set(get_pr_type(subscript),act_P_MAC_addr) then begin
 set_H_bit(get_pr_type(subscript),act_P_MAC_addr);
 output LS_System_Access_point.TIMER_request(
  Query_time,"Query_Timer",subscript);
end;

end; "Query_Timer": begin

act_P_MAC_addr       := get_P_MAC_addr(subscript);
send_pdu.hwtype      := ethernet;
send_pdu.prtype      := get_pr_type(subscript);
send_pdu.HW_length   := fddi_addr_length;
send_pdu.PR_length   := get_pr_length(send_pdu.prtype);
send_pdu.PR_sender   := get_my_pr_addr(send_pdu.prtype);
send_pdu.PR_receiver := get_broadcast_addr(send_pdu.prtype);
if Q_bit_set(get_pr_type(subscript),act_P_MAC_addr) then begin
 send_pdu.HW_1      := My_P_MAC_addr;

Kuehn [Page 26] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

 send_pdu.HW_2      := My_S_MAC_addr;
 send_pdu.operation := request;
 PDU := assemble_dmarp_pdu(send_pdu);
 output SNAP2_LSSAP.UNITDATA_request(
  My_S_MAC_addr,get_S_MAC_addr(send_pdu.prtype,act_P_MAC_addr),
  dmarp_QoS,PDU);
 delete_entry(subscript);
end else begin
 send_pdu.HW_1      := My_S_MAC_addr;
 send_pdu.HW_2      := get_P_MAC_addr(subscript);
 send_pdu.operation := query;
 PDU := assemble_dmarp_pdu(send_pdu);
 output SNAP2_LSSAP.UNITDATA_request(
  My_S_MAC_addr,get_S_MAC_addr(send_pdu.prtype,send_pdu.HW_2),
  dmarp_QoS,PDU);
 set_Q_bit(send_pdu.prtype,send_pdu.HW_2);

end; end; end; end; end; (* body *)

11. Summary

 The introduction of the load sharing layer in the protocol layering
 of the dual MAC stations allows the application of IP and ARP on
 inhomogeneous FDDI rings. The protocol suite of single MAC stations
 needs no modification.
 By the load sharing layer, the property "dual MAC" is transparent for
 ARP, IP and the higher layer protocols.
 In dual MAC stations, any load sharing criteria may be implemented in
 the multiplexer of the load sharing entity.  The conversion of
 addresses, the exchange of address and reachability information
 between dual MAC stations and the proper transmission of multicast
 and broadcast frames is taken upon by the load sharing entity.

12. References

  [1] ANSI, "FDDI Station Management (SMT)", ANSI
      X3T9/90-X3T9.5/84-49 Rev 6.2, May 1990.
  [2] ANSI, "FDDI Media Access Control (MAC-2)",
      X3T9/90-X3T9.5/88-139 Rev 3.2, June 1990.
  [3] ISO, "Information processing systems- Local area networks-
      Part 2: Logical link control", ISO 8802-2:1989, August 1989.
  [4] IEEE, "Draft Standard P802.1A Overview and Architecture",
      P802.1A/D9-89/74, September 1989.

Kuehn [Page 27] RFC 1329 Address Resolution for Dual MAC FDDI Networks May 1992

  [5] Plummer, C., "An Ethernet Address Resolution Protocol --or--
      Converting Network Protocol Addresses to 48.bit Ethernet
      Address for Transmission on Ethernet Hardware", RFC 826, MIT,
      November 1982.
  [6] Reynolds, J., and Postel, J., "Assigned Numbers", RFC 1060,
      USC/Information Sciences Institute, March 1990.
  [7] Postel, J., "Internet Protocol", RFC 791, USC/Information
      Sciences Institute, September 1981.
  [8] Katz, D., "A Proposed Standard for the Transmission of IP
      Datagrams over FDDI Networks", RFC 1188, Merit/NSFNET,
      October 1990.
  [9] Internet Engineering Task Force, Braden, R., Editor,
      "Requirements for Internet Hosts -- Communication Layers",
      RFC 1122, IETF, October 1989.
 [10] Katz, D., "The Use of Connectionless Network Layer Protocols
      over FDDI Networks", Merit/NSFNET, 1990.

13. Security Considerations

 Security issues are not discussed in this memo.

14. Author's Address

 Peter Kuehn
 Raiffeisenstrasse 9b
 8933 Untermeitingen
 Germany
 Phone: .. 82 32 / 7 46 02
 EMail: thimmela@sniabg.wa.sni.de

Kuehn [Page 28]

1)
dmarp_pdu.operation = error) or (dmarp_pdu.operation = reply
/data/webs/external/dokuwiki/data/pages/rfc/rfc1329.txt · Last modified: 1992/05/19 01:05 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki