Q149270: How Routers Handle IPX Type 20 NetBIOS Packets
Article: Q149270
Product(s): Microsoft Windows NT
Version(s): 3.1 3.5 3.51 4.0
Operating System(s):
Keyword(s): kbnetwork
Last Modified: 09-AUG-2001
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The information in this article applies to:
- Microsoft Windows NT Server version 3.1
- Microsoft Windows NT Workstation version 3.1
- Microsoft Windows NT Advanced Server, version 3.1
- Microsoft Windows NT Workstation versions 3.5, 3.51, 4.0
- Microsoft Windows NT Server versions 3.5, 3.51, 4.0
- Microsoft Windows 95
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SUMMARY
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NetBIOS provides session-layer services like packet assembly-disassembly and
named addressing for Microsoft's NWLink protocol. NetBIOS, like SPX, also
provides guaranteed packet delivery and packet sequencing on the Transport
layer. For NetBIOS to operate within an NWLink environment, routers must be able
to propagate NetBIOS packets across the network. This is done by defining a
specific IPX packet for NetBIOS. Since IPX is a derivative of XNS's IDP
protocol, it follows the assigned packet types given by Xerox as shown below:
Protocol Packet type (hex)
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Unknown 00
Routing information 01
Echo 02
Error 03
Packet exchange protocol (PEP) 04
Sequence packet exchange (SPX) 05
Experimental 10
NetWare core protocol 11
NetBIOS 14
Packet type 20 (0x14) identifies a NetBIOS packet and is designated as a
propagated packet. The Destination Node field in the IPX header is set to
0xFFFFFFFFFFFF. When this packet is received by a router, the router checks the
IPX header Packet Type field. If the Packet Type is 20 (0x14), the router
examines the Transport Control field. If the Transport Control field is more
than 8, the router will discard the packet. (A type 20 packet is propagated over
a maximum of 8 networks.) The router then compares the value in the Network
Number field with the network number of the segment it received the packet from.
If these match, the router discards the packet to prevent it from being sent
over the same segment twice. The router then puts the network number of the
segment it received the packet from in the next available Network Number field
and increments the Transport Control field before broadcasting the packet to all
directly connected network segments not represented in the Network Number
fields.
Additional query words: IPX NWLINK TYPE 20 ROUTER ROUTING ntfaqmax
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Keywords : kbnetwork
Technology : kbWinNTsearch kbWinNTWsearch kbWinNTW400 kbWinNTW400search kbWinNT351search kbWinNT350search kbWinNT400search kbWinNTW350 kbWinNTW350search kbWinNTW351search kbWinNTW351 kbWinNTW310 kbWinNTSsearch kbWinNTS400search kbWinNTS400 kbWinNTS351 kbWinNTS350 kbWinNTS310 kbWinNTAdvSerSearch kbWinNTAdvServ310 kbWinNTS351search kbWinNTS350search kbWinNTS310search kbWin95search kbWinNT310Search kbWinNTW310Search kbZNotKeyword3
Version : 3.1 3.5 3.51 4.0
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