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       Saturday, 25-Nov-2017 01:21:00 Central Standard Time

1

Windows 2000 and XP definitions.

These Definitions are taken direct from the Microsoft White pages at Technet. Its been shortened to only include the information for the entries in the Cablenut adjuster. Enjoy !



1. DefaultReceiveWindow - The number of receive bytes that AFD buffers on a connection before imposing flow control. For some applications, a larger value here gives slightly better performance at the expense of increased resource utilization.

Value Type: REG_DWORD

Default: 4096/8192/8192


2. DefaultSendWindow - This is similar to DefaultReceiveWindow, but for the send side of connections.

Value Type: REG_DWORD

Default: 4096/8192/8192


3. DisableAddressSharing - This parameter is used to prevent address sharing (SO_REUSEADDR) between processes so that if a process opens a socket, no other process can steal data from it.

Value Type: REG_DWORD

Default: 0

Range: 0, 1


4. InitialLargeBufferCount - The count of large buffers allocated by AFD at system startup. Allocate more buffers to improve performance at the cost of physical memory.

Value Type: REG_DWORD

Default: 0/2/10


5. InitialMediumBufferCount - Initial count of medium buffers.

Value Type: REG_DWORD

Default: 4/8/24


6. InitialSmallBufferCount - Initial count of small buffers.

Value Type: REG_DWORD

Default: 8/16/32


7. LargeBufferSize - The size, in bytes, of large buffers used by AFD. Smaller values use less memory and larger
values can improve performance.

Value Type: REG_DWORD

Default: PAGE_SIZE (4096 bytes on i386, 8192 bytes on Alpha)


8. MaxFastTransmit - This parameter controls the maximum amount of data that is transferred in a TransmitFile request on the fast path. Fast I/O is essentially copying data and bypassing the I/O subsystem, instead of mapping memory and going through the I/O subsystem. This is advantageous for small amounts of data.

Value Type: REG_DWORD

Valid Range: 0–0xffffffff

Default: 64 KB


9. MediumBufferSize - The size in bytes of medium buffers used by AFD.

Value Type: REG_DWORD

Default: 1504


10. PriorityBoost - The priority boost that AFD gives to a thread when it completes I/O for that thread. If a multithreaded application experiences starvation of some threads, the problem may be remedied by reducing this value.

Value Type: REG_DWORD

Default: 2

Valid Range: 0–16


11. SmallBufferSize - The size in bytes of small buffers used by AFD.

Value Type: REG_DWORD

Default: 128


12. TransmitWorker - This parameter controls how Afd.sys uses system threads. Setting it to 0x10 causes AFD to use system threads to perform IO that results from a long (more than 2 SendPacketLength worth of data) TransmitFile request. Setting it to 0x20 causes AFD to use kernel-mode APC for IO and to execute everything in the context of the same thread. This is new in Windows 2000 and can improve performance by reducing the number of context switches in long TransmitFile requests.

Value Type: REG_DWORD

Default: 0x10

Valid Range: 0x10, 0x20


13. FastSendDatagramThreshold - Datagrams smaller than the value of this parameter go through the fast I/O path or are buffered on send. Larger ones are held until the datagram is actually sent. The default value was found by testing to be the best overall value for performance. Fast I/O means copying data and bypassing the I/O subsystem, instead of mapping memory and going through the I/O subsystem. This is advantageous for small amounts of data.

Value Type: REG_DWORD

Default: 1024


14. EnableFastRouteLookup - Fast route look-up is enabled if this flag is set. This can make route lookups faster at the expense of non-paged pool memory. This parameter is created by the Routing and Remote Access Service.

Value Type: REG_DWORD—Boolean

Valid Range: 0, 1 (false, true)

Default: 0 (false)


15. EnablePMTUDiscovery - Setting this parameter to 1 (True) causes TCP to attempt to discover the Maximum
Transmission Unit (MTU or largest packet size) over the path to a remote machine. By discovering the Path MTU and limiting TCP segments to this size, TCP can eliminate fragmentation at routers along the path which connect networks with different MTUs. Fragmentation adversely affects TCP throughput and network congestion.

Value Type: REG_DWORD—Boolean

Valid Range: 0, 1 (false, true)

Default: 1 (true)


16. IgnorePushBitOnReceives - Normally, Windows 2000 completes a Windows Sockets Receive when one of the following occurs:

* Data arrives with the push bit set.

* The user recv buffer is full.

* 0.5 seconds have elapsed since any data arrived.

Setting this parameter to a 1 causes Afd.sys to treat all incoming packets as though the push bit was set. This
should only be done when necessary to work around client TCP/IP implementations that are not properly pushing data.

Value Type: REG_DWORD—Boolean

Valid Range: 0, 1 (false, true)

Default: 0 (false)


17. GlobalMaxTcpWindowSize - The TcpWindowSize parameter can be used to set the receive window on a per-interface basis. This parameter can be used to set a global limit for the TCP window size on a system-wide basis.

Value Type: REG_DWORD—Number of bytes

Valid Range: 0–0x3FFFFFFF

Default: This parameter does not exist by default.


18. MaxFreeTcbs - This parameter controls the number of cached (pre-allocated) Transport Control Blocks (TCBs) that are available. A Transport Control Block is a data structure that is maintained for each TCP connection.

Value Type: REG_DWORD—number

Valid Range: 0–0xFFFFFFFF

Default: The following default values are used (note that small is defined as a computer with less than19 MB of RAM, medium is 19–63 MB of RAM, and large is 64 MB or more of RAM. Although this code still exists, nearly all computers are large now).

Windows 2000 Professional:

* Small system—250
* Medium system—500
* Large system—1000 


19. MaxHashTableSize - This value should be set to a power of 2 (for example, 512, 1024, 2048, and so on.) If this value is not a power of 2, the system configures the hash table to the next power of 2 value (for example, a setting of 513 is rounded up to 1024.) This value controls how fast the system can find a TCP control block and should be increased if MaxFreeTcbs is increased from the default.

Value Type: REG_DWORD—number (must be a power of 2)

Valid Range: 0x40–0x10000 (64-65536 decimal)

Default: 512


20. MaxNormLookupMemory - This parameter controls the maximum amount of memory that the system allows for the route table data and the routes themselves. It is designed to prevent memory exhaustion on the computer caused by adding large numbers of routes.

Value Type: REG_DWORD—number

Valid Range: Any DWORD (0xFFFFFFFF means no limit on memory.)

For Windows 2000 Professional:

150,000 bytes, which accommodates 1000 routes.


21. SackOpts - This parameter controls whether or not Selective Acknowledgment (SACK, specified in RFC 2018) support is enabled.

Value Type: REG_DWORD—Boolean

Valid Range: 0, 1 (false, true)

Default: 1 (true)


22. SynAttackProtect - Synattack protection involves reducing the amount of retransmissions for the SYN-ACKS, which will reduce the time for which resources have to remain allocated. The allocation of route cache entry resources is delayed until a connection is made. If synattackprotect = 2, then the connection indication to AFD is delayed until the three-way handshake is completed. Note that the actions taken by the protection mechanism only occur if TcpMaxHalfOpen and TcpMaxHalfOpenRetried settings are exceeded.

Value Type: REG_DWORD

Valid Range: 0, 1, 2

0 (no synattack protection)
1 (reduced retransmission retries and delayed RCE (route cache entry) creation if the TcpMaxHalfOpen and TcpMaxHalfOpenRetried settings are satisfied.)
2 (in addition to 1 a delayed indication to Winsock is made.)

Default: 0 (false)


23. Tcp1323Opts - This parameter controls RFC 1323 time stamps and window-scaling options. Time stamps and window scaling are enabled by default, but can be manipulated with flag bits. Bit 0 controls window scaling, and bit 1 controls time stamps.

Value Type: REG_DWORD—number (flags)

Valid Range: 0, 1, 2, 3

0 (disable RFC 1323 options)
1 (window scale enabled only)
2 (timestamps enabled only)
3 (both options enabled)


Default: No value; the default behavior is as follows: do not initiate options but if requested provide them.


24. TcpLogLevel - Specifies how verbose TCP/IP should be about logging events in the event log. The highest level of verbosity is 16, and 1 is the lowest level.

Value Type: REG_DWORD

Level  Events to be included
  ---------------------------------------------
  1    Only the most critical errors
  4    Serious protocol violations
  8    Nonserious protocol violations
  12    Information about unusual events
  16    Information about unusual events that
        some networks normally allow

Default: 16


25. TcpMaxDupAcks - This parameter determines the number of duplicate ACKs that must be received for the same sequence number of sent data before fast retransmit is triggered to resend the segment that has been dropped in transit.

Value Type: REG_DWORD—number

Valid Range: 1–3

Default: 2


26. TcpMaxHalfOpen - This parameter controls the number of connections in the SYN-RCVD state allowed before SYN-ATTACK protection begins to operate.

Value Type: REG_DWORD—number

Valid Range: 100–0xFFFF

Default: 100 (Professional)


27. TcpMaxHalfOpenRetried - This parameter controls the number of connections in the SYN-RCVD state for which there has been at least one retransmission of the SYN sent, before SYN-ATTACK attack protection begins to operate.

Value Type: REG_DWORD—number

Valid Range: 80–0xFFFF

Default: 80 (Professional)


28. TcpRecvSegmentSize - Specifies the maximum receive segment size.

Value Type: REG_DWORD

Default: 1460
 

29. TcpSendSegmentSize - Specifies the maximum send segment size.

Value Type: REG_DWORD

Default: 1460


30. TcpTimedWaitDelay - Determines the time that must elapse before TCP can release a closed connection and reuse its resources.

Value Type: REG_DWORD—time in seconds

Valid Range: 30-300 (decimal)

Default: 0xF0 (240 decimal)


31. TcpUseRFC1122UrgentPointer - This parameter determines whether TCP uses the RFC 1122 specification for urgent data or the mode used by BSD- derived systems.

Value Type: REG_DWORD—Boolean

Valid Range: 0, 1 (false, true)

Default: 0 (false)


32. TcpWindowSize - This parameter determines the maximum TCP receive window size offered by the system. The receive window specifies the number of bytes a sender may transmit without receiving an acknowledgment. In general, larger receive windows will improve performance over high (delay * bandwidth ) networks. For highest efficiency, the receive window should be an even multiple of the TCP Maximum Segment Size (MSS).

Value Type: REG_DWORD—number of bytes

Valid Range: 0–0x3FFFFFFF


33. MaxConnectionsPer1_0Server & MaxConnectionsPerServer - HTTP specification requires that no one computer can have more than 2 simultaneous connections to any single HTTP server. This will affect all Windows application that uses the standard API, including Internet Explorer. People who keep multiple files on an online hard drive hate this restriction, because they can only download two or four files at a time. Windows developers choose to limit the maximum connections to a HTTP 1.0 server to four. In the HTTP 1.1 specification the number of connections was mandated to 2.

Value Type: REG_DWORD

Default: 4, 2


34. DefaultTTL - Specifies the default Time To Live (TTL) value set in the header of outgoing IP packets. The TTL
determines the maximum amount of time an IP packet may live in the network without reaching its destination.

Value Type: REG_DWORD—Number of seconds/hops

Valid Range: 0–0xff (0–255 decimal)

Default: 128


35. DisableUserTOSSetting - This parameter can be used to allow programs to manipulate the Type Of Service (TOS) bits in the header of outgoing IP packets.

Value Type: REG_DWORD—Boolean

Valid Range: 0, 1 (false, true)

Default: 1 (true)


36. TcpMaxDataRetransmissions - This parameter controls the number of times that TCP retransmits an individual data segment (not connection request segments) before aborting the connection.

Value Type: REG_DWORD—number

Valid Range: 0–0xFFFFFFFF

Default: 5


37. DefaultTOSvalue - The IP header in every datagram specifies a Type of Service (ToS) value that can be used to specify the quality of service (QoS) setting for IP datagrams. The ToS value indicates the military origin of the protocol because it was designed for the Advanced Research Project Agency Networks that was the predecessor to the current Internet.

Value Type: REG_DWORD

Valid Range: 0255

Default: 0


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