LAN Manager LANAs on MS-DOS Workstations (97881)




This article was previously published under Q97881

SUMMARY

This article explains how protocol-driver/network-adapter pairs are numbered and how sending, receiving, and processing orders are determined using these numbers and network operational methods. The information is categorized under subheads; it includes examples and suggestions for enhancing performance.

MORE INFORMATION

LANA Numbers

LANA #:

LANA numbers provide the LAN Manager redirector a way to identify a unique combination of one protocol driver and one network adapter (NIC) MAC driver. LANA numbers are assigned automatically, and are based on LANA bases.

LANA Base:

A LANA base is a unique number assigned to a protocol stack. It serves as the starting LANA number for the first protocol\MAC combination, and each subsequent protocol\MAC binding combination is numbered in sequence starting from it. LANA bases are specified in the PROTOCOL.INI file. 
          NetBEUI           TCP/IP
LANA base   (0)              (2)
           |   \             / 
           |     \         / 
           |       \     / 
           |         \ / 
           |         / \ 
           |       /     \ 
           |     /         \ 
           |   /             \ 
LANA #:    (0)(2)             (1)
          Ethernet         Token Ring
Example:

NetBEUI has a LANA base of 0. It is bound to two NICs--Ethernet and token ring. The first protocol\MAC combination of NetBEUI\Ethernet has a LANA number of 0. The second combination of NetBEUI\token ring is a number in sequence starting from 0, which gives it a LANA number of 1. If NetBEUI is bound to a third NIC it would have a LANA Number of 2, and so on. NetBEUI only responds to LANAs 0 and 1.

TCP/IP has a LANA base of 2. It is bound to one NIC, and that combination is uniquely identified by the LANA number of 2. TCP/IP responds only to LANA 2.

Note: In LAN Manager, TCP/IP can be bound only to one NIC at a time.

Sending Order

Once again, this information only applies to MS-DOS LAN Manager workstations with multiple protocols. During discovery (the NCB_Call for NET USE command), the redirector specifies the LANA number to try in the NCB [NetBIOS Control Block]. The NCB is a command destined for the protocol driver. The sequence in which the redirector specifies the LANA numbers is determined by one of two methods.

Method 1--WRKNETS:

This parameter is found in the LANMAN.INI [WORKSTATION] section. It allows you to specify to the redirector the order in which LANA numbers are to be attempted when sending frames. Sending order is most important when doing discovery (the NCB_Call) for a new resource NetBIOS name\physical network address. After a resource is found and a session is established, future frames are sent directly to this LANA number. Values for WRKNETS are the actual LANA numbers.

Example:

WRKNETS=2,0,1

Following the previous example, a frame is sent out in this order: on TCP/IP\Ethernet (LANA 2); NetBEUI\Ethernet (LANA 0); and NetBEUI\token ring (LANA 1). When a proper response (Name_Recognized) is received over one of the LANAs, the remaining LANAs are not attempted.

Method 2--No WRKNETS:

If WRKNETS is not specified, the redirecter fills in the LANA field in the NCB with the actual LANA numbers--lowest to highest.

The INT 5c Factor - Load Order

When protocol drivers are loaded, they hook Int 5c. If more drivers are loaded, they will be chained on this interrupt. After the redirector builds the NCB and specifies the first LANA number (see example above) to send the frame on, it calls Int 5C with a pointer to the NCB. The last driver loaded will take a look at the LANA number. If it does not own that number, it will pass it down the chain to the next previously loaded protocol, which checks the LANA number and so on until a match is found. The protocol that owns the LANA then process the NCB and submits the frame on the wire. 
                           Redirector <<-------- LANMAN.INI WRKNETS = 1,0,2
                           |      |
            ---------------|      |
            |                     |
            V                     V
          INT 5c                 NCB - [... SMB, LANA#, ...]
          ------
[reverse]  TCP/IP (LANA# 2)
[load   ]  NetBEUI(LANA# 1,0)
[order  ]
In this example:

  • NetBEUI is loaded first by the LOAD NETBEUI command in AUTOEXEC.BAT.
  • TCP/IP is loaded via the LOAD TCPIP command in AUTOEXEC.BAT.
  • Note: Chain is FILO--first in last out--so TCP is first in chain.
  • Redirector builds NCB with SMB, NCB command, etc. and LANA number.
  • LANA number order is supplied from WRKNETS so the first number is 1.
  • Redir calls Int 5c with a pointer to the NCB structure.
  • TCP/IP driver is the last driver loaded, so it gets first chance to look at the LANA number.
  • TCP knows that its LANA is 2. LANA Base <= LANA # <= (LANA base + number of TCP bindings).
  • NCB LANA is 1, so the TCP driver passes control to the next protocol in the chain, which is NetBEUI.
  • NetBEUI recognizes that LANA 1 is one of his LANAs, so it processes the NCB and submits the frame on the wire.
Tuning:

For the best performance:

  • Place the LANA of your most used protocol first in the WRKNETS parameter. This factor is the most important one.
  • Load your most used protocol driver last so that it will be first to look at the LANA number in the INT 5c chain.

Receiving Order - One MAC Driver:

For this example, assume one MAC driver (one NIC). Incoming frames are passed to each protocol driver until recognized. If a TCP frame arrives, it may be first passed to NetBEUI, which does not recognize the frame and rejects it. The frame may then be passed to the TCP/IP stack that recognizes it, and there be processed. There are two ways to determine which protocol receives an incoming frame in a particular order.

User Defined - PRIORITY:

The PRIORITY parameter in the PROTOCOL.INI (PROTMAN) section can be used to hardcode the receive order. For example: 
   PRIORITY = NETBEUI, XNS, TCPIP
Incoming frames are passed to NetBEUI first, XNS second, and TCP/IP last.

Programmed Default:

If no PRIORITY is specified, the default mechanism takes effect. This algorithm attempts to give a frame to the protocol stack most likely to assign ownership quickly. The order is:

  1. Non LLC frames--looks at DIX type.

    TCP/IP (optional frame type)
  2. LLC frames with specific LSAPs--DSAP field contains protocol type.

    NetBEUI, DLC
  3. LLC frames with non-specific LSAPs--DSAP contains "AA." Type will follow later in frame.

    NBP
Each frame type must look further into the frame to determine protocol type, so the protocol that has to look the least distance into the frame is the fastest.

The vector module component manages passing the frame to multiple protocol stacks. The vector module is loaded by PROTMAN.

Receiving Order - Multi MAC Drivers:

In a multi protocol/multi MAC driver configuration, a vector module is loaded for each MAC driver (NIC). The receiving mechanism can now be derived from the previous discussion.

Other Notes:

  • LAN Manager supports up to a theoretical maximum of 12 networks (LANAs).
  • NetBEUI can be bound to a theoretical maximum of eight MAC drivers.
  • TCP/IP can be bound to only one MAC driver.
Reference(s):

For more information, query on the following words in the Microsoft Knowledge Base:

MS-DOS and NET and LOGON and LANAs and Validation

Modification Type: Major Last Reviewed: 7/30/2001
Keywords: KB97881
©2002 Microsoft Corporation. All rights reserved.