“Windows Networking”

ITL

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Overview

• Networking under Windows

• Mixture of applications and protocols

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Windows Protocols

• Application Layer:– “Providers”: Vendor-specific networking clients– Application (http, ftp, etc.)

• Presentation Layer– Usually empty

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Windows Protocols

• Session Layer– Redirectors – linked to Provider modules– Servers

• Transport Layer– TDI – Transport Driver Interface– Various transport protocols (TCP, NWLink, NBF)

• Lower Layers

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Some Definitions

• NBF: NetBIOS Frame Protocol– Based on NetBEUI (Network Basic Input Output

System Extended User Interface)

• NWLink– Implementation of the Novell protocols IPX/SPX

• IPX: Internet Packet Exchange• SPX: Sequence Packet Exchange

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Protocol Structure

NetBIOS (Kernel)TCP/IPNetBT

SPX/IPX NBF

NDIS NIC Driver

Note:

TCP/NetBT and IPX/SPX are routable, NBF (NetBEUI) is not.

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Specifications & Info• Karanjit S. Siyan, “Windows NT TCP/IP”, New Riders

Professional Library• RFCs 1001 & 1002• SNIA CIFS Spec 0.9

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Some History

• Windows networking – Windows for Workgroups

– LAN Manager (various versions)

• Intended for small LANs

• Similar to AppleTalk

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History …

• Novell used for server-based large networks

• Windows networking used for Peer-to-Peer

• RFCs 1001 and 1002 define NetBIOS over TCP (NetBT)

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UNC

• Uniform Naming Convention– \\ServerName\ShareName\Path\FileName

• Defines a flat namespace used to locate network resources

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SMB

• Server Message Block– Application layer protocol

– Defines access to files, printers, and named pipes

• SMB specs are not public

• CIFS specs are public under SNIA

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Protocol Stacks for SMB

SMB

NetBIOS

TCP/IP NetBEUIIPX/SPX

Data Link Layer

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SMB Functions

• Session Setup and Disconnect

• File Access

• Printer Access

• Directory Searching

• Setting File Attributes

• File Creation and Deletion

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SMB File Access

• Open and Close

• Read and Write

• Record and byte range locking

• File Locks

• “Opportunistic” locks (caching support)

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SMB Variants

• SMB is not a single specification

• Microsoft and other vendors made numerous enhancements

• SMB session setups include a required version negotiation

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Name Resolution

• NetBIOS uses 15 character names

• Flat name space inside a NetBIOS Scope

• Nodes assert a name upon startup

• Assertion is successful unless challenged

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Node Types• b-nodes

– Use broadcast for name resolution– Can interact only with b-nodes (and

mixed nodes)

• p-nodes– Use a NetBIOS name server (NBNS,

Microsoft WINS)– Cannot interact with b-nodes

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Mixed Node Types

• m-nodes – mixed operation, broadcast first

• h-nodes– mixed, NBNS, LMHOST file, broadcst

• Windows defaults:– b-node– h-node if a WINS server is specified

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Some Notes

• WINS is NBNS as defined in RCFs 1001 and 1002, but

• WINS replications (server to server updates) are vendor-specific

• WINS is dynamic, entries come from NetBIOS name registration at system startup

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WINS and DNS

• Up to Windows NT 4, these are separate– Computers can have unrelated DNS

and NetBIOS names

• DHCP clients without dynamic DNS– Have “generic” or no DNS names– Dynamically register NetBIOS names

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Windows 2000

• Pure Windows 2000 networks use dynamic DNS

• WINS lookups used for mixed environments

• Names lookups can trigger– DNS queries– WINS queries– Broadcasts

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WINS and DNS names

• Windows 2000 machines use FQDN (Fully Qualified Domain Names)

• NetBIOS names are derived from the host name– Pad short names with spaces up to

15 characters– Truncate names with >15 chars

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Microsoft DNS

• Dynamic Updates• Replication (If used with Active

Directory aka LDAP)• UTF-8 character coding unless

restricted to RFC 1123• Additional DNS record types

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Service Discovery

• LDAP - based starting with Windows 2000

• Previous versions use a proprietary systen of “domain browsers”

• Creates some broadcast traffic

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Access Control in SMB• “Share Level Access”

– Used with FAT16 and FAT32– Single password for a directory tree

• User Level Access– Requires User/Password

Authentication– NTFS required to make access file-

specific

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Security Models

• “Workgroup”– relies on share level security or– user/password settings on Windows

NT or 2000 workstations

• Domain Controller– Windows NT or 2000 server which

contains a central user database

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Dual Access Control

• NTFS-based file sharing checks credentials twice– Share-level permissions– File level access control lists

• Non-file objects (e.g. printers) can have share permissions

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Security protocols in CIFS

• Authentication required for session setup to a server– Plain Text Password (discouraged for

obvious reason)– Challenge-response

• Requires a shared secret (password)• May be stored on a separate

authentication server