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101-767: SMB was originally developed in 1983 by Barry A. Feigenbaum at IBM to share access to files and printers across a network of systems running IBM's IBM PC DOS . In 1987, Microsoft and 3Com implemented SMB in LAN Manager for OS/2 , at which time SMB used the NetBIOS service atop the NetBIOS Frames protocol as its underlying transport. Later, Microsoft implemented SMB in Windows NT 3.1 and has been updating it ever since, adapting it to work with newer underlying transports: TCP/IP and NetBT . SMB over QUIC

202-433: A decentralized approach is often used, where every user may make their local folders and printers available to others. This approach is sometimes denoted a Workgroup or peer-to-peer network topology, since the same computer may be used as client as well as server. In large enterprise networks, a centralized file server or print server , sometimes denoted client–server paradigm , is typically used. A client process on

303-593: A free-software re-implementation (using reverse engineering ) of the SMB/CIFS networking protocol for Unix-like systems, initially to implement an SMB server to allow PC clients running the DEC Pathworks client to access files on SunOS machines. Because of the importance of the SMB protocol in interacting with the widespread Microsoft Windows platform, Samba became a popular free software implementation of

404-428: A CPU-style MMU. Digital signal processors have similarly generalized over the years. Earlier designs used scratchpad memory fed by direct memory access , but modern DSPs such as Qualcomm Hexagon often include a very similar set of caches to a CPU (e.g. Modified Harvard architecture with shared L2, split L1 I-cache and D-cache). A memory management unit (MMU) that fetches page table entries from main memory has

505-473: A backing store. Memoization is an optimization technique that stores the results of resource-consuming function calls within a lookup table, allowing subsequent calls to reuse the stored results and avoid repeated computation. It is related to the dynamic programming algorithm design methodology, which can also be thought of as a means of caching. A content delivery network (CDN) is a network of distributed servers that deliver pages and other Web content to

606-524: A cache benefits one or both of latency and throughput ( bandwidth ). A larger resource incurs a significant latency for access – e.g. it can take hundreds of clock cycles for a modern 4 GHz processor to reach DRAM. This is mitigated by reading large chunks into the cache, in the hope that subsequent reads will be from nearby locations and can be read from the cache. Prediction or explicit prefetching can be used to guess where future reads will come from and make requests ahead of time; if done optimally,

707-424: A cache for frequently accessed data, providing high speed local access to frequently accessed data in the cloud storage service. Cloud storage gateways also provide additional benefits such as accessing cloud object storage through traditional file serving protocols as well as continued access to cached data during connectivity outages. The BIND DNS daemon caches a mapping of domain names to IP addresses , as does

808-677: A compatible SMB client and server to allow non-Windows operating systems, such as Unix-like operating systems, to interoperate with Windows. As of version 3 (2003), Samba provides file and print services for Microsoft Windows clients and can integrate with a Windows NT 4.0 server domain, either as a Primary Domain Controller (PDC) or as a domain member. Samba4 installations can act as an Active Directory domain controller or member server, at Windows 2008 domain and forest functional levels. Package managers in Linux distributions can search for

909-669: A drive with drive letter C: on a Windows machine. A shared drive or folder is often mapped at the client PC computer, meaning that it is assigned a drive letter on the local PC computer. For example, the drive letter H: is typically used for the user home directory on a central file server. A network share can become a security liability when access to the shared files is gained (often by devious means) by those who should not have access to them. Many computer worms have spread through network shares. Network shares would consume extensive communication capacity in non-broadband network access. Because of that, shared printer and file access

1010-623: A lack of support for newer authentication protocols like NTLMv2 and Kerberos in favor of protocols like NTLMv1, LanMan , or plaintext passwords. Real-time attack tracking shows that SMB is one of the primary attack vectors for intrusion attempts, for example the 2014 Sony Pictures attack , and the WannaCry ransomware attack of 2017. In 2020, two SMB high-severity vulnerabilities were disclosed and dubbed as SMBGhost ( CVE-2020-0796 ) and SMBleed ( CVE-2020-1206 ), which when chained together can provide RCE (Remote Code Execution) privilege to

1111-630: A large variety of SMB clients and servers. SMB1 features many versions of information for commands (selecting what structure to return for a particular request) because features such as Unicode support were retro-fitted at a later date. SMB2 involves significantly reduced compatibility-testing for implementers of the protocol. SMB2 code has considerably less complexity since far less variability exists (for example, non-Unicode code paths become redundant as SMB2 requires Unicode support). Apple migrated to SMB2 (from their own Apple Filing Protocol , now legacy) starting with OS X 10.9 "Mavericks" . This transition

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1212-487: A local cache of remote files, allowing offline access and synchronization when reconnected. The first international heterogenous network for resource sharing was the 1973 interconnection of the ARPANET with early British academic networks through the computer science department at University College London (UCL). Cache (computing) In computing , a cache ( / k æ ʃ / KASH )

1313-448: A multiprotocol, identity-aware platform for network access to files used in OEM storage products built on Linux/Unix based devices. The platform could be used for traditional NAS, Cloud Gateway, and Cloud Caching devices for providing secure access to files across a network. Likewise was purchased by EMC Isilon in 2012. KSMBD is an open source in-kernel CIFS/SMB server implementation for

1414-451: A network share can be addressed according to the following: where ServerComputerName is the WINS name, DNS name or IP address of the server computer, and ShareName may be a folder or file name, or its path . The shared folder can also be given a ShareName that is different from the folder local name at the server side. For example, \\ ServerComputerName \c$ usually denotes

1515-485: A network with a smaller number of hosts, increased broadcast traffic can cause problems as the number of hosts on the network increases. The implementation of name resolution infrastructure in the form of Windows Internet Naming Service (WINS) or Domain Name System (DNS) resolves this problem. WINS was a proprietary implementation used with Windows NT 4.0 networks, but brought about its own issues and complexities in

1616-419: A network. However the SMB itself does not use broadcasts—the broadcast problems commonly associated with SMB actually originate with the NetBIOS service location protocol. By default, a Microsoft Windows NT 4.0 server used NetBIOS to advertise and locate services. NetBIOS functions by broadcasting services available on a particular host at regular intervals. While this usually makes for an acceptable default in

1717-436: A new opportunistic locking mechanism. SMB 3.0 (previously named SMB 2.2) was introduced with Windows 8 and Windows Server 2012 . It brought several significant changes that are intended to add functionality and improve SMB2 performance, notably in virtualized data centers : It also introduces several security enhancements, such as end-to-end encryption and a new AES based signing algorithm. SMB 3.0.2 (known as 3.02 at

1818-476: A resolver library. Write-through operation is common when operating over unreliable networks (like an Ethernet LAN), because of the enormous complexity of the coherency protocol required between multiple write-back caches when communication is unreliable. For instance, web page caches and client-side network file system caches (like those in NFS or SMB ) are typically read-only or write-through specifically to keep

1919-414: A result or reading from a slower data store; thus, the more requests that can be served from the cache, the faster the system performs. To be cost-effective, caches must be relatively small. Nevertheless, caches are effective in many areas of computing because typical computer applications access data with a high degree of locality of reference . Such access patterns exhibit temporal locality, where data

2020-411: A secondary name resolution protocol for interoperability with legacy Windows environments and applications. Further, Microsoft DNS servers can forward name resolution requests to legacy WINS servers in order to support name resolution integration with legacy (pre-Windows 2000) environments that do not support DNS. Network designers have found that latency has a significant impact on the performance of

2121-558: A server, an operating system on the server that supports access to its resources from a client, and an application layer (in the four or five layer TCP/IP reference model ) file sharing protocol and transport layer protocol to provide that shared access. Modern operating systems for personal computers include distributed file systems that support file sharing, while hand-held computing devices sometimes require additional software for shared file access. The most common such file systems and protocols are: The "primary operating system"

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2222-465: A specialized cache, used for recording the results of virtual address to physical address translations. This specialized cache is called a translation lookaside buffer (TLB). Information-centric networking (ICN) is an approach to evolve the Internet infrastructure away from a host-centric paradigm, based on perpetual connectivity and the end-to-end principle , to a network architecture in which

2323-504: A specific function are the D-cache , I-cache and the translation lookaside buffer for the memory management unit (MMU). Earlier graphics processing units (GPUs) often had limited read-only texture caches and used swizzling to improve 2D locality of reference . Cache misses would drastically affect performance, e.g. if mipmapping was not used. Caching was important to leverage 32-bit (and wider) transfers for texture data that

2424-451: A system writes data to cache, it must at some point write that data to the backing store as well. The timing of this write is controlled by what is known as the write policy . There are two basic writing approaches: A write-back cache is more complex to implement since it needs to track which of its locations have been written over and mark them as dirty for later writing to the backing store. The data in these locations are written back to

2525-459: A tag matching that of the desired data, the data in the entry is used instead. This situation is known as a cache hit . For example, a web browser program might check its local cache on disk to see if it has a local copy of the contents of a web page at a particular URL . In this example, the URL is the tag, and the content of the web page is the data. The percentage of accesses that result in cache hits

2626-532: A transport (a largely experimental effort that required further refinement). Microsoft submitted some partial specifications as Internet Drafts to the IETF . These submissions have since expired. Microsoft introduced a new version of the protocol (SMB 2.0 or SMB2) in 2006 with Windows Vista and Windows Server 2008 . Although the protocol is proprietary, its specification has been published to allow other systems to interoperate with Microsoft operating systems that use

2727-410: A user, based on the geographic locations of the user, the origin of the web page and the content delivery server. CDNs began in the late 1990s as a way to speed up the delivery of static content, such as HTML pages, images and videos. By replicating content on multiple servers around the world and delivering it to users based on their location, CDNs can significantly improve the speed and availability of

2828-492: A website or application. When a user requests a piece of content, the CDN will check to see if it has a copy of the content in its cache. If it does, the CDN will deliver the content to the user from the cache. A cloud storage gateway, also known as an edge filer, is a hybrid cloud storage device that connects a local network to one or more cloud storage services , typically object storage services such as Amazon S3 . It provides

2929-410: Is a shared disk file system , where each computer has access to the "native" filesystem on a shared disk drive. Shared resource access can also be implemented with Web-based Distributed Authoring and Versioning (WebDAV). The share can be accessed by client computers through some naming convention, such as UNC (Universal Naming Convention) used on DOS and Windows PC computers. This implies that

3030-600: Is a family of portable SMB client and server implementations developed by Visuality Systems , an Israel-based company established in 1998 by Sam Widerman, formerly the CEO of Siemens Data Communications. The NQ family comprises an embedded SMB stack (written in C), a Pure Java SMB Client, and a storage SMB Server implementation. All solutions support the latest SMB 3.1.1 dialect. NQ for Linux , NQ for WinCE , iOS, Android, VxWorks and other real-time operating systems are all supported by

3131-422: Is a hardware or software component that stores data so that future requests for that data can be served faster; the data stored in a cache might be the result of an earlier computation or a copy of data stored elsewhere. A cache hit occurs when the requested data can be found in a cache, while a cache miss occurs when it cannot. Cache hits are served by reading data from the cache, which is faster than recomputing

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3232-444: Is a proprietary SMB server implementation developed by Tuxera that can be run either in kernel or user space . It supports SMB 3.1.1 and all previous versions, additionally advanced SMB features like continuous availability (persistent handles) scale-out, RDMA (SMB Direct), SMB multichannel, transparent compression, shadow copy . Likewise developed a CIFS/SMB implementation (versions 1.0, 2.0, 2.1 and NFS 3.0) in 2009 that provided

3333-401: Is a variant of LRU designed for the situation where the stored contents in cache have a valid lifetime. The algorithm is suitable in network cache applications, such as ICN, content delivery networks (CDNs) and distributed networks in general. TLRU introduces a new term: time to use (TTU). TTU is a time stamp on content which stipulates the usability time for the content based on the locality of

3434-435: Is a web cache that is shared among all users of that network. Another form of cache is P2P caching , where the files most sought for by peer-to-peer applications are stored in an ISP cache to accelerate P2P transfers. Similarly, decentralised equivalents exist, which allow communities to perform the same task for P2P traffic, for example, Corelli. A cache can store data that is computed on demand rather than retrieved from

3535-475: Is an Internet service. Shared file access is transparent to the user, as if it was a resource in the local file system, and supports a multi-user environment. This includes concurrency control or locking of a remote file while a user is editing it, and file system permissions . Shared file access involves but should not be confused with file synchronization and other information synchronization. Internet-based information synchronization may, for example, use

3636-482: Is an example of disk cache, is managed by the operating system kernel . While the disk buffer , which is an integrated part of the hard disk drive or solid state drive, is sometimes misleadingly referred to as "disk cache", its main functions are write sequencing and read prefetching. Repeated cache hits are relatively rare, due to the small size of the buffer in comparison to the drive's capacity. However, high-end disk controllers often have their own on-board cache of

3737-405: Is an extremely chatty protocol, which is not such an issue on a local area network (LAN) with low latency. It becomes very slow on wide area networks (WAN) as the back and forth handshake of the protocol magnifies the inherent high latency of such a network. Later versions of the protocol reduced the high number of handshake exchanges. One approach to mitigating the inefficiencies in the protocol

3838-435: Is known as the hit rate or hit ratio of the cache. The alternative situation, when the cache is checked and found not to contain any entry with the desired tag, is known as a cache miss . This requires a more expensive access of data from the backing store. Once the requested data is retrieved, it is typically copied into the cache, ready for the next access. During a cache miss, some other previously existing cache entry

3939-428: Is made up of a pool of entries. Each entry has associated data , which is a copy of the same data in some backing store . Each entry also has a tag , which specifies the identity of the data in the backing store of which the entry is a copy. When the cache client (a CPU, web browser, operating system ) needs to access data presumed to exist in the backing store, it first checks the cache. If an entry can be found with

4040-431: Is normally prohibited in firewalls from computers outside the local area network or enterprise Intranet . However, by means of virtual private networks (VPN), shared resources can securely be made available for certified users outside the local network. A network share is typically made accessible to other users by marking any folder or file as shared, or by changing the file system permissions or access rights in

4141-407: Is notable for its now-common scheme of representing symlinks. This "Minshall-French" format shows symlinks as textual files with a .symlink extension and a Xsym\n magic number, always 1067 bytes long. This format is also used for storing symlinks on native SMB servers or unsupported filesystems. Samba supports this format with an mfsymlink option. Docker on Windows also seems to use it. NQ

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4242-409: Is read or written for the first time is effectively being buffered; and in the case of a write, mostly realizing a performance increase for the application from where the write originated. Additionally, the portion of a caching protocol where individual writes are deferred to a batch of writes is a form of buffering. The portion of a caching protocol where individual reads are deferred to a batch of reads

4343-556: Is requested that has been recently requested, and spatial locality, where data is requested that is stored near data that has already been requested. In memory design, there is an inherent trade-off between capacity and speed because larger capacity implies larger size and thus greater physical distances for signals to travel causing propagation delays . There is also a tradeoff between high-performance technologies such as SRAM and cheaper, easily mass-produced commodities such as DRAM , flash , or hard disks . The buffering provided by

4444-702: Is the operating system on which the file sharing protocol in question is most commonly used. On Microsoft Windows , a network share is provided by the Windows network component "File and Printer Sharing for Microsoft Networks", using Microsoft's SMB ( Server Message Block ) protocol. Other operating systems might also implement that protocol; for example, Samba is an SMB server running on Unix-like operating systems and some other non-MS-DOS/non-Windows operating systems such as OpenVMS . Samba can be used to create network shares which can be accessed, using SMB, from computers running Microsoft Windows . An alternative approach

4545-1045: Is to use WAN optimization products such as those provided by Riverbed , Silver Peak , or Cisco . A better approach is to upgrade to a later version of SMB. This includes upgrading both NAS devices as well as Windows Server 2003. The most effective method to identify SMB1 traffic is with a network analyzer tool, such as Wireshark . Microsoft also provides an auditing tool in Windows Server 2016 to track down devices that use SMB1. Microsoft has marked SMB1 as deprecated in June 2013. Windows Server 2016 and Windows 10 version 1709 do not have SMB1 installed by default. In 1996, when Sun Microsystems announced WebNFS , Microsoft launched an initiative to rename SMB to Common Internet File System (CIFS) and added more features, including support for symbolic links , hard links , larger file sizes, and an initial attempt at supporting direct connections over TCP port 445 without requiring NetBIOS as

4646-413: Is typically removed in order to make room for the newly retrieved data. The heuristic used to select the entry to replace is known as the replacement policy . One popular replacement policy, least recently used (LRU), replaces the oldest entry, the entry that was accessed less recently than any other entry. More sophisticated caching algorithms also take into account the frequency of use of entries. When

4747-554: The IETF , partly in response to formal IETF standardization of version 4 of the Network File System in December 2000 as IETF RFC 3010; however, those SMB-related Internet-Drafts expired without achieving any IETF standards-track approval or any other IETF endorsement. (See http://ubiqx.org/cifs/Intro.html for historical detail.) SMB2 is also a relatively clean break with the past. Microsoft's SMB1 code has to work with

4848-521: The Kerberos protocol to authenticate users against Active Directory on Windows domain networks. On simpler, peer-to-peer networks, SMB uses the NTLM protocol. Windows NT 4.0 SP3 and later can digitally sign SMB messages to prevent some man-in-the-middle attacks . SMB signing may be configured individually for incoming SMB connections (by the "LanmanServer" service) and outgoing SMB connections (by

4949-486: The SyncML language. Shared file access is based on server-side pushing of folder information, and is normally used over an "always on" Internet socket . File synchronization allows the user to be offline from time to time and is normally based on an agent software that polls synchronized machines at reconnect, and sometimes repeatedly with a certain time interval, to discover differences. Modern operating systems often include

5050-461: The TCP and IP protocols for transport. This combination allows file sharing over complex, interconnected networks , including the public Internet. The SMB server component uses TCP port 445. SMB originally operated on NetBIOS over IEEE 802.2 - NetBIOS Frames or NBF - and over IPX/SPX , and later on NetBIOS over TCP/IP (NetBT), but Microsoft has since deprecated these protocols. On NetBT,

5151-506: The cifs-utils package. The package is from the Samba maintainers. NSMB (Netsmb and SMBFS) is a family of in-kernel SMB client implementations in BSD operating systems. It was first contributed to FreeBSD 4.4 by Boris Popov, and is now found in a wide range of other BSD systems including NetBSD and macOS . The implementations have diverged significantly ever since. The macOS version of NSMB

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5252-484: The file transfer protocol (FTP), or the Bluetooth IRDA OBject EXchange (OBEX) protocol. Shared access involves automatic synchronization of folder information whenever a folder is changed on the server, and may provide server side file searching, while file transfer is a more rudimentary service. Shared file access is normally considered as a local area network (LAN) service, while FTP

5353-503: The page cache associated with a prefetcher or the web cache associated with link prefetching . Small memories on or close to the CPU can operate faster than the much larger main memory . Most CPUs since the 1980s have used one or more caches, sometimes in cascaded levels ; modern high-end embedded , desktop and server microprocessors may have as many as six types of cache (between levels and functions). Some examples of caches with

5454-514: The "LanmanWorkstation" service). The default setting for Windows domain controllers running Windows Server 2003 and later is to not allow unsigned incoming connections. As such, earlier versions of Windows that do not support SMB signing from the get-go (including Windows 9x ) cannot connect to a Windows Server 2003 domain controller. SMB supports opportunistic locking (see below) on files in order to improve performance. Opportunistic locking support has changed with each Windows Server release. In

5555-570: The CIFS moniker but continues developing SMB and publishing subsequent specifications. Samba is a free software reimplementation of the SMB protocol and the Microsoft extensions to it. Server Message Block (SMB) enables file sharing , printer sharing , network browsing, and inter-process communication (through named pipes ) over a computer network . SMB serves as the basis for Microsoft's Distributed File System implementation. SMB relies on

5656-410: The Linux kernel. Compared to user-space implementations, it provides better performance and makes it easier to implement some features such as SMB Direct. It supports SMB 3.1.1 and previous versions. Over the years, there have been many security vulnerabilities in Microsoft's implementation of the protocol or components on which it directly relies. Other vendors' security vulnerabilities lie primarily in

5757-415: The SMB 1.0 protocol, that it performs more poorly than other protocols like FTP . Monitoring reveals a high degree of "chattiness" and a disregard of network latency between hosts. For example, a VPN connection over the Internet will often introduce network latency. Microsoft has explained that performance issues come about primarily because SMB 1.0 is a block-level rather than a streaming protocol, that

5858-422: The SMB are proprietary and were initially closed, thereby forcing other vendors and projects to reverse-engineer the protocol to interoperate with it. The SMB 1.0 protocol was eventually published some time after it was reverse engineered, whereas the SMB 2.0 protocol was made available from Microsoft's Open Specifications Developer Center from the outset. In 1991, Andrew Tridgell started the development of Samba,

5959-421: The SMB protocol, opportunistic locking is a mechanism designed to improve performance by controlling caching of network files by the client. Unlike traditional locks , opportunistic lock (OpLocks) are not strictly file locking or used to provide mutual exclusion. There are four types of opportunistic locks. The use of the SMB protocol has often correlated with a significant increase in broadcast traffic on

6060-502: The aim of turning DOS INT 21h local file access into a networked file system. Microsoft made considerable modifications to the most commonly used version and included SMB support in the LAN Manager operating system it had started developing for OS/2 with 3Com around 1990. Microsoft continued to add features to the protocol in Windows for Workgroups ( c.  1992 ) and in later versions of Windows. LAN Manager authentication

6161-418: The amount of information that needs to be transmitted across the network, as information previously stored in the cache can often be re-used. This reduces bandwidth and processing requirements of the web server, and helps to improve responsiveness for users of the web. Web browsers employ a built-in web cache, but some Internet service providers (ISPs) or organizations also use a caching proxy server, which

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6262-431: The attacker. Shared access In computing , a shared resource , or network share , is a computer resource made available from one host to other hosts on a computer network . It is a device or piece of information on a computer that can be remotely accessed from another computer transparently as if it were a resource in the local machine. Network sharing is made possible by inter-process communication over

6363-409: The backing store only when they are evicted from the cache, a process referred to as a lazy write . For this reason, a read miss in a write-back cache will often require two memory backing store accesses to service: one for the write back, and one to retrieve the needed data. Other policies may also trigger data write-back. The client may make many changes to data in the cache, and then explicitly notify

6464-486: The cache ahead of time. Anticipatory paging is especially helpful when the backing store has a long latency to read the first chunk and much shorter times to sequentially read the next few chunks, such as disk storage and DRAM. A few operating systems go further with a loader that always pre-loads the entire executable into RAM. A few caches go even further, not only pre-loading an entire file, but also starting to load other related files that may soon be requested, such as

6565-448: The cache is a network-level solution. Therefore, it has rapidly changing cache states and higher request arrival rates; moreover, smaller cache sizes impose different requirements on the content eviction policies. In particular, eviction policies for ICN should be fast and lightweight. Various cache replication and eviction schemes for different ICN architectures and applications have been proposed. The time aware least recently used (TLRU)

6666-452: The cache is divided into two partitions called privileged and unprivileged partitions. The privileged partition can be seen as a protected partition. If content is highly popular, it is pushed into the privileged partition. Replacement of the privileged partition is done by first evicting content from the unprivileged partition, then pushing content from the privileged partition to the unprivileged partition, and finally inserting new content into

6767-404: The cache to write back the data. Since no data is returned to the requester on write operations, a decision needs to be made whether or not data would be loaded into the cache on write misses. Both write-through and write-back policies can use either of these write-miss policies, but usually they are paired. Entities other than the cache may change the data in the backing store, in which case

6868-493: The case of file-handles , thereby removing previous constraints on block sizes, which improves performance with large file transfers over fast networks. Windows Vista/ Server 2008 and later operating systems use SMB2 when communicating with other machines also capable of using SMB2. SMB1 continues in use for connections with older versions of Windows, as well various vendors' NAS solutions. Samba 3.5 also includes experimental support for SMB2. Samba 3.6 fully supports SMB2, except

6969-447: The configurable NQ solution. MoSMB is a user space SMB implementation for Linux. It supports SMB 2.x and SMB 3.x. Key features include Cloud-scale Active-Active Scale-out Clusters, SMB Direct (RDMA), SMB Multichannel, Transparent Failover and Continuous Availability. MoSMB also supports Amazon S3 object storage as storage backend in addition to POSIX file systems such as ext4 , ZFS , Lustre , Ceph , etc. Fusion File Share by Tuxera

7070-517: The content and information from the content publisher. Owing to this locality-based time stamp, TTU provides more control to the local administrator to regulate in-network storage. In the TLRU algorithm, when a piece of content arrives, a cache node calculates the local TTU value based on the TTU value assigned by the content publisher. The local TTU value is calculated by using a locally-defined function. Once

7171-551: The context of operating systems and LAN and Intranet services, for example in Microsoft Windows documentation. Though, as BitTorrent and similar applications became available in the early 2000s, the term file sharing increasingly has become associated with peer-to-peer file sharing over the Internet. Shared file and printer access require an operating system on the client that supports access to resources on

7272-525: The copy in the cache may become out-of-date or stale . Alternatively, when the client updates the data in the cache, copies of those data in other caches will become stale. Communication protocols between the cache managers that keep the data consistent are associated with cache coherence . On a cache read miss, caches with a demand paging policy read the minimum amount from the backing store. A typical demand-paging virtual memory implementation reads one page of virtual memory (often 4 KB) from disk into

7373-415: The data item to its residing storage at a later stage or else occurring as a background process. Contrary to strict buffering, a caching process must adhere to a (potentially distributed) cache coherency protocol in order to maintain consistency between the cache's intermediate storage and the location where the data resides. Buffering, on the other hand, With typical caching implementations, a data item that

7474-408: The data item to realize a performance increase by virtue of being able to be fetched from the cache's (faster) intermediate storage rather than the data's residing location. With write caches, a performance increase of writing a data item may be realized upon the first write of the data item by virtue of the data item immediately being stored in the cache's intermediate storage, deferring the transfer of

7575-493: The design and maintenance of a Microsoft network. Since the release of Windows 2000, the use of WINS for name resolution has been deprecated by Microsoft, with hierarchical Dynamic DNS now configured as the default name resolution protocol for all Windows operating systems. Resolution of (short) NetBIOS names by DNS requires that a DNS client expand short names, usually by appending a connection-specific DNS suffix to its DNS lookup queries. WINS can still be configured on clients as

7676-571: The disk cache in RAM. A typical CPU reads a single L2 cache line of 128 bytes from DRAM into the L2 cache, and a single L1 cache line of 64 bytes from the L2 cache into the L1 cache. Caches with a prefetch input queue or more general anticipatory paging policy go further—they not only read the data requested, but guess that the next chunk or two of data will soon be required, and so prefetch that data into

7777-450: The focal point is identified information. Due to the inherent caching capability of the nodes in an ICN, it can be viewed as a loosely connected network of caches, which has unique requirements for caching policies. However, ubiquitous content caching introduces the challenge to content protection against unauthorized access, which requires extra care and solutions. Unlike proxy servers, in ICN

7878-645: The hard disk drive's data blocks. Finally, a fast local hard disk drive can also cache information held on even slower data storage devices, such as remote servers (web cache) or local tape drives or optical jukeboxes ; such a scheme is the main concept of hierarchical storage management . Also, fast flash-based solid-state drives (SSDs) can be used as caches for slower rotational-media hard disk drives, working together as hybrid drives or solid-state hybrid drives (SSHDs). Web browsers and web proxy servers employ web caches to store previous responses from web servers, such as web pages and images . Web caches reduce

7979-621: The latency is bypassed altogether. The use of a cache also allows for higher throughput from the underlying resource, by assembling multiple fine-grain transfers into larger, more efficient requests. In the case of DRAM circuits, the additional throughput may be gained by using a wider data bus. Hardware implements cache as a block of memory for temporary storage of data likely to be used again. Central processing units (CPUs), solid-state drives (SSDs) and hard disk drives (HDDs) frequently include hardware-based cache, while web browsers and web servers commonly rely on software caching. A cache

8080-456: The local TTU value is calculated the replacement of content is performed on a subset of the total content stored in cache node. The TLRU ensures that less popular and short-lived content should be replaced with incoming content. The least frequent recently used (LFRU) cache replacement scheme combines the benefits of LFU and LRU schemes. LFRU is suitable for network cache applications, such as ICN, CDNs and distributed networks in general. In LFRU,

8181-606: The local computer. Network access to the pre-shared folder can be turned on. In the English version of the Windows XP Home Edition operating system, the preshared folder is named Shared documents , typically with the path C:\Documents and Settings\All users\Shared documents . In Windows Vista and Windows 7 , the pre-shared folder is named Public documents , typically with the path C:\Users\Public\Public documents . In home and small office networks,

8282-489: The local user computer takes the initiative to start the communication, while a server process on the file server or print server remote computer passively waits for requests to start a communication session In very large networks, a Storage Area Network (SAN) approach may be used. Online storage on a server outside the local network is currently an option, especially for homes and small office networks. Shared file access should not be confused with file transfer using

8383-468: The modification of user quotas using the Windows quota management tools. When SMB2 was introduced it brought a number of benefits over SMB1 for third party implementers of SMB protocols. SMB1, originally designed by IBM , was reverse engineered , and later became part of a wide variety of non-Windows operating systems such as Xenix , OS/2 and VMS ( Pathworks ). X/Open standardized it partially; Microsoft had submitted Internet-Drafts describing SMB2 to

8484-417: The network protocol simple and reliable. Search engines also frequently make web pages they have indexed available from their cache. For example, Google provides a "Cached" link next to each search result. This can prove useful when web pages from a web server are temporarily or permanently inaccessible. Database caching can substantially improve the throughput of database applications, for example in

8585-417: The network. Some examples of shareable resources are computer programs , data , storage devices , and printers . E.g. shared file access (also known as disk sharing and folder sharing ), shared printer access, shared scanner access, etc. The shared resource is called a shared disk , shared folder or shared document The term file sharing traditionally means shared file access, especially in

8686-443: The new protocol. SMB2 reduces the 'chattiness' of the SMB 1.0 protocol by reducing the number of commands and subcommands from over a hundred to just nineteen. It has mechanisms for pipelining , that is, sending additional requests before the response to a previous request arrives, thereby improving performance over high- latency links. It adds the ability to compound multiple actions into a single request, which significantly reduces

8787-418: The number of round-trips the client needs to make to the server, improving performance as a result. SMB1 also has a compounding mechanism—known as AndX—to compound multiple actions, but Microsoft clients rarely use AndX. It also introduces the notion of "durable file handles": these allow a connection to an SMB server to survive brief network outages, as are typical in a wireless network, without having to incur

8888-485: The overhead of re-negotiating a new session. SMB2 includes support for symbolic links . Other improvements include caching of file properties, improved message signing with HMAC SHA-256 hashing algorithm and better scalability by increasing the number of users, shares and open files per server among others. The SMB1 protocol uses 16-bit data sizes, which amongst other things, limits the maximum block size to 64K. SMB2 uses 32- or 64-bit wide storage fields, and 128 bits in

8989-535: The privileged partition. In the above procedure, the LRU is used for the privileged partition and an approximated LFU (ALFU) scheme is used for the unprivileged partition. The basic idea is to cache the locally popular content with the ALFU scheme and push the popular content to the privileged partition. In 2011, the use of smartphones with weather forecasting options was overly taxing AccuWeather servers; two requests within

9090-499: The process of caching and the process of buffering. Fundamentally, caching realizes a performance increase for transfers of data that is being repeatedly transferred. While a caching system may realize a performance increase upon the initial (typically write) transfer of a data item, this performance increase is due to buffering occurring within the caching system. With read caches, a data item must have been fetched from its residing location at least once in order for subsequent reads of

9191-412: The processing of indexes , data dictionaries , and frequently used subsets of data. A distributed cache uses networked hosts to provide scalability, reliability and performance to the application. The hosts can be co-located or spread over different geographical regions. The semantics of a "buffer" and a "cache" are not totally different; even so, there are fundamental differences in intent between

9292-412: The properties of the folder. For example, a file or folder may be accessible only to one user (the owner), to system administrators, to a certain group of users to public, i.e. to all logged in users. The exact procedure varies by platform. In operating system editions for homes and small offices, there may be a special pre-shared folder that is accessible to all users with a user account and password on

9393-460: The same park would generate separate requests. An optimization by edge-servers to truncate the GPS coordinates to fewer decimal places meant that the cached results from the earlier query would be used. The number of to-the-server lookups per day dropped by half. While CPU caches are generally managed entirely by hardware, a variety of software manages other caches. The page cache in main memory, which

9494-455: The server component uses three TCP or UDP ports: 137 (NETBIOS Name Service), 138 (NETBIOS Datagram Service), and 139 (NETBIOS Session Service). In Microsoft Windows, two vaguely named Windows services implement SMB. The "Server" service (ID: LanmanServer ) is in charge of serving shared resources . The "Workstation" service (ID: LanmanWorkstation ) maintains the computer name and helps access shared resources on other computers. SMB uses

9595-610: The time) was introduced with Windows 8.1 and Windows Server 2012 R2; in those and later releases, the earlier SMB version 1 can be optionally disabled to increase security. SMB 3.1.1 was introduced with Windows 10 and Windows Server 2016 . This version supports AES-128 GCM encryption in addition to AES-128 CCM encryption added in SMB3, and implements pre-authentication integrity check using SHA-512 hash. SMB 3.1.1 also makes secure negotiation mandatory when connecting to clients using SMB versions that support it. The specifications for

9696-449: Was fraught with compatibility problems though. Non-default support for SMB2 appeared in fact in OS X 10.7, when Apple abandoned Samba in favor of its own SMB implementation called SMBX after Samba adopted GPLv3 . The Linux kernel 's CIFS client file system has SMB2 support since version 3.7. SMB 2.1, introduced with Windows 7 and Server 2008 R2, introduced minor performance enhancements with

9797-582: Was implemented based on the original legacy SMB specification's requirement to use IBM "LAN Manager" passwords, but implemented DES in a flawed manner that allowed passwords to be cracked. Later, Kerberos authentication was also added. The Windows domain logon protocols initially used 40-bit encryption outside of the United States , because of export restrictions on stronger 128-bit encryption (subsequently lifted in 1996 when President Bill Clinton signed Executive Order 13026 ). SMB 1.0 (or SMB1)

9898-605: Was introduced in Windows Server 2022 . In 1996, Microsoft published a version of SMB 1.0 with minor modifications under the Common Internet File System ( CIFS / s ɪ f s / ) moniker. CIFS was compatible with even the earliest incarnation of SMB, including LAN Manager 's. It supports symbolic links, hard links, and larger file size, but none of the features of SMB 2.0 and later. Microsoft's proposal, however, remained an Internet Draft and never achieved standard status. Microsoft has since discontinued

9999-449: Was often as little as 4 bits per pixel. As GPUs advanced, supporting general-purpose computing on graphics processing units and compute kernels , they have developed progressively larger and increasingly general caches, including instruction caches for shaders , exhibiting functionality commonly found in CPU caches. These caches have grown to handle synchronization primitives between threads and atomic operations , and interface with

10100-460: Was originally designed for small LANs ; it has a block size that is limited to 64K, SMB signing creates an additional overhead and the TCP window size is not optimized for WAN links. Solutions to this problem include the updated SMB 2.0 protocol, Offline Files , TCP window scaling and WAN optimization devices from various network vendors that cache and optimize SMB 1.0 and 2.0. Barry Feigenbaum originally designed SMB at IBM in early 1983 with

10201-536: Was originally designed to run on NetBIOS Frames (NetBIOS over IEEE 802.2 ). Since then, it has been adapted to NetBIOS over IPX/SPX (NBX), and NetBIOS over TCP/IP (NetBT). Also, since Windows 2000 , SMB runs on TCP using TCP port 445, a feature known as "direct host SMB". There is still a thin layer (similar to the Session Message packet of NetBT's Session Service) between SMB and TCP. Windows Server 2003, and legacy NAS devices use SMB1 natively. SMB1

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