Browse Definitions:
Definition

Layer 4-7 (network services)

This definition is part of our Essential Guide: Essential Guide: Application-aware networking
Contributor(s): Lisa Phifer

Layer 4 through Layer 7 are services delivered by the upper layers of the Open Systems Interconnection (OSI) communication model. Layer 4-7 services, sometimes referred to as the upper layers, support end-to-end communication between a source and destination application and are used whenever a message passes from or to a user.

Providing Layer 4-7 services involves sitting somewhere in the middle of the network delivery path and using that vantage point to apply new services without requiring change to applications on either end. The list of possible Layer 4-7 services is effectively infinite in a cloud computing or software-defined networking (SDN) infrastructure because they can be built in the upper layers of the OSI model, largely independent of the underlying network. For example, SDN can change Layer 4-7 network services by enabling virtual applications of load balancing, WAN acceleration and virtual security appliances.

Layer 4, the Transport Layer, ensures end-to-end delivery of messages for both "connection-mode" data such as TCP connections and "connectionless-mode" data such as UDP datagrams. For both modes, the endpoints of communication are identified by port numbers such as TCP port 80 or UDP port 161.

Layer 5, the Session Layer, provides services for coordinating communication between applications and synchronizing message delivery. For example, a protocol with suspend/resume or checkpoint/rollback capabilities includes session layer services such as ITU X.225, AppleTalk or RPC.

Layer 6, the Presentation Layer, provides services for converting data from local format (abstract syntax) into a machine-independent format (transfer syntax). Many application protocols are defined in Abstract Syntax Notation One (ASN.1) notation. ASN.1 defines a set of data structures mapped to encoding rules – for example, how an Integer should be encoded into a bit string to be transmitted to and decoded by a recipient using XML Encoding Rules (XER).

Layer 7, the Application Layer provides common services used by applications to establish, release and abort communication with each other, as well as specific services. Most applications “live” at Layer 7, including the File Transfer Protocol (FTP), the Simple Mail Transfer Protocol (SMTP), the Post Office Protocol (POP), the Hyper Text Transfer Protocol (HTTP) and the Domain Name System Protocol (DNS).

 

 

 

 

 

This was last updated in April 2013

Continue Reading About Layer 4-7 (network services)

Join the conversation

1 comment

Send me notifications when other members comment.

By submitting you agree to receive email from TechTarget and its partners. If you reside outside of the United States, you consent to having your personal data transferred to and processed in the United States. Privacy

Please create a username to comment.

layer4-7真心不好做分析清理
Cancel

-ADS BY GOOGLE

File Extensions and File Formats

SearchCompliance

  • internal audit (IA)

    An internal audit (IA) is an organizational initiative to monitor and analyze its own business operations in order to determine ...

  • pure risk (absolute risk)

    Pure risk, also called absolute risk, is a category of threat that is beyond human control and has only one possible outcome if ...

  • risk assessment

    Risk assessment is the identification of hazards that could negatively impact an organization's ability to conduct business.

SearchSecurity

  • computer exploit

    A computer exploit, or exploit, is an attack on a computer system, especially one that takes advantage of a particular ...

  • cyberwarfare

    Cyberwarfare is computer- or network-based conflict involving politically motivated attacks by a nation-state on another ...

  • insider threat

    Insider threat is a generic term for a threat to an organization's security or data that comes from within.

SearchHealthIT

SearchDisasterRecovery

  • business continuity and disaster recovery (BCDR)

    Business continuity and disaster recovery (BCDR) are closely related practices that describe an organization's preparation for ...

  • business continuity plan (BCP)

    A business continuity plan (BCP) is a document that consists of the critical information an organization needs to continue ...

  • call tree

    A call tree -- sometimes referred to as a phone tree -- is a telecommunications chain for notifying specific individuals of an ...

SearchStorage

  • OpenStack Block Storage (Cinder)

    OpenStack Block Storage (Cinder) is open source software designed to create and manage a service that provides persistent data ...

  • SATA Express (SATAe)

    SATA Express (SATAe or Serial ATA Express) is a bus interface to connect storage devices to a computer motherboard, supporting ...

  • DIMM (dual in-line memory module)

    A DIMM (dual in-line memory module) is the standard memory card used in servers and PCs.

SearchSolidStateStorage

  • 3D XPoint

    3D XPoint is memory storage technology jointly developed by Intel and Micron Technology Inc.

  • RRAM or ReRAM (resistive RAM)

    RRAM or ReRAM (resistive random access memory) is a form of nonvolatile storage that operates by changing the resistance of a ...

  • JEDEC

    JEDEC is a global industry group that develops open standards for microelectronics.

SearchCloudStorage

  • Google Cloud Storage

    Google Cloud Storage is an enterprise public cloud storage platform that can house large unstructured data sets.

  • RESTful API

    A RESTful application program interface breaks down a transaction to create a series of small modules, each of which addresses an...

  • cloud storage infrastructure

    Cloud storage infrastructure is the hardware and software framework that supports the computing requirements of a private or ...

Close