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Product Details 

The S8300 Media Server resides inside a G700, G350 or G250 Media Gateway. It can

be used as a standalone communication system or as a fully surivable remote

gateway. The S8300 can be the primary controller for up to 50 remote G250, G350 and G700 Media

Gateways.

As with the S8400, S8500 and S8700 series Media Servers, the S8300 supports the Linux operating

system and it is powered by Communication Manager. It supports industry standard call control, quality

of service, management functions, and IP, digital, and analog endpoints.

Manufacturing Info 

The S8300 Media Server is an Avaya Product manufactured by Celestica in Monterrey, Mexico.

Avaya IP Office

Avaya IP Office is an all-in-one solution specially designed to meet the

communications challenges facing the home office, small office and

medium enterprise with two to 360 extensions.

Built on Avaya`s latest advancements in converged voice and data

technology, you can benefit from many of the advantages sophisticated

communications deliver to your business. Use it as a voice solution,

employing either IP technology, more traditional telephony or a

combination of both and you can benefit from a comprehensive set of 

telephony features. Use it as a data solution to deliver both local area and

wide area networking capability. And because it`s an all in one solution you

can use it as a converged solution delivering both your voice and data requirements. Avaya IP Office can

help businesses to improve productivity in the work place. Integrated messaging, voice mail and autoattendant can help your staff to manage calls and messages more efficiently. Support for remote

working is an integral part of the portfolio.

The full Avaya IP Office solution is easily managed through Avaya IP Office Manager, a Microsoft®

Windows®-based PC software application. Every Avaya IP Office platform protects your investments by

supporting common software, telephones, applications and a range of device and user capacity.

Expansion modules help you meet your changing or growing needs while retaining the cost-

effectiveness of your original investment.

Vmware

VMW is a company providing virtualization software founded in 1998 and based in USA. It is majorilyowned by EMC Corporation.VMware's desktop software runs on Microsoft Windows, Linux, and Mac OS

X, while VMware's enterprise software hypervisors for servers, VMware ESX and VMware ESXi, are bare-

metal embedded hypervisors that run directly on server hardware without requiring an additional

underlying operating system. 

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While VMware Infrastructure 3.5 was in development, vSphere was conceived as an enhanced suite of 

tools with cloud computing utilizing VMware ESX/ESXi 4.The cloud computing-enabled tool suite was

spun off  as VMware Infrastructure 4 (for short, VI 4) parallel to but distinct from VMware Infrastructure

3.5 (VI 3.5) that was then ready for release (March 30, 2009).VMware eventually announced vSphere 4

instead of VI 4 on April 21, 2009 and released it on May 21, 2009.VMware released Update 1 for

vSphere 4 on November 19, 2009 to add support for Windows 7 and Windows Server 2008 R2. 

VMware's vSphere 4.1 began shipping in August 2010. This update included an updated vCenter

Configuration Manager as well as vCenter Application Discovery Manager, and the ability of vMotion to

move more than one virtual machine at a time from one server host to another.VMware released

Update 1 for vSphere 4.1 on 10 February, 2011 to add support for RHEL 6, RHEL 5.6, SLES 11 SP1 for

VMware, Ubuntu 10.10, and Solaris 10 Update 9.A secret installation of vSphere was used by a

disgruntled former employee to wipe out a New Jersey based pharmaceutical company's VMware

installation in February of 2011, costing a reported $800,000 loss.

DHCP

The Dynamic Host Configuration Protocol (DHCP) is a network configuration protocol for hosts on

Internet Protocol (IP) networks. Computers that are connected to IP networks must be configured

before they can communicate with other hosts. The most essential information needed is an IP address, 

and a default route and routing prefix. DHCP eliminates the manual task by a network administrator. It

also provides a central database of devices that are connected to the network and eliminates duplicate

resource assignments.In addition to IP addresses, DHCP also provides other configuration information,

particularly the IP addresses of local caching DNS resolvers, network boot servers, or other service hosts.

DHCP is used for IPv4 as well as IPv6. While both versions perform much the same purpose, the details

of the protocol for IPv4 and IPv6 are sufficiently different that they may be considered separateprotocols.Hosts that do not use DHCP for address configuration may still use it to obtain other

configuration information. Alternatively, IPv6 hosts may use stateless address autoconfiguration. IPv4

hosts may use link-local addressing to achieve limited local connectivity.

Name server

In computing, a name server (also spelled nameserver) is a program or computer server that

implements a name-service protocol. It maps a human-recognizable identifier to a system-internal,

often numeric, identification or addressing component.The most prominent types of name servers in

operation today are the name servers of the Domain Name System (DNS), one of the two principal name

spaces of the Internet. The most important function of these DNS servers is the translation (resolution)

of humanly memorable domain names and hostnames into the corresponding numeric Internet Protocol 

(IP) addresses, the second principal Internet name space which is used to identify and locate computer

systems and resources on the Internet.

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FTP

File Transfer Protocol (FTP) is a standard network protocol used to transfer files from one host to

another host over a TCP-based network, such as the Internet. FTP is built on a client-server architecture

and utilizes separate control and data connections between the client and server.FTP users may

authenticate themselves using a clear-text sign-in protocol but can connect anonymously if the server isconfigured to allow it.The first FTP client applications were interactive command-line tools,

implementing standard commands and syntax. Graphical user interface clients have since been

developed for many of the popular desktop operating systems in use today.

LAN

A local area network (LAN) is a computer network that interconnects computers in a limited area such as

home, school, computer laboratory or office building.[1] The defining characteristics of LANs, in contrast

to wide area networks (WANs), include their usually higher data-transfer rates, smaller geographic area,

and lack of a need for leased telecommunication lines.ARCNET, Token Ring and other technology

standards have been used in the past, but Ethernet over twisted pair cabling, and Wi-Fi are the two

most common technologies currently used to build LANs.

Standards evolution

The development and proliferation of  personal computers using the CP/M operating system in the late

1970s, and later DOS-based systems starting in 1981, meant that many sites grew to dozens or even

hundreds of computers. The initial driving force for networking was generally to share storage and

printers, which were both expensive at the time. There was much enthusiasm for the concept and for

several years, from about 1983 onward, computer industry pundits would regularly declare the coming

year to be “the year of the LAN”. 

In practice, the concept was marred by proliferation of incompatible physical layer and network protocol 

implementations, and a plethora of methods of sharing resources. Typically, each vendor would have its

own type of network card, cabling, protocol, and network operating system. A solution appeared with

the advent of  Novell NetWare which provided even-handed support for dozens of competing card/cable

types, and a much more sophisticated operating system than most of its competitors. Netware

dominated[12] the personal computer LAN business from early after its introduction in 1983 until the

mid 1990s when Microsoft introduced Windows NT Advanced Server and Windows for Workgroups. 

Of the competitors to NetWare, only Banyan Vines had comparable technical strengths, but Banyan

never gained a secure base. Microsoft and 3Com worked together to create a simple network operating

system which formed the base of 3Com's 3+Share, Microsoft's LAN Manager and IBM's LAN Server - but

none of these were particularly successful.

During the same period, Unix computer workstations from vendors such as Sun Microsystems, Hewlett-

Packard, Silicon Graphics, Intergraph, NeXT and Apollo were using TCP/IP based networking. Although

this market segment is now much reduced, the technologies developed in this area continue to be

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influential on the Internet and in both Linux and Apple Mac OS X networking—and the TCP/IP protocol

has now almost completely replaced IPX, AppleTalk, NBF, and other protocols used by the early PC LANs.

Cabling

Early LAN cabling had always been based on various grades of  coaxial cable. However shielded twisted

pair was used in IBM's Token Ring implementation, and in 1984 StarLAN showed the potential of simple

unshielded twisted pair by using Cat3—the same simple cable used for telephone systems. This led to

the development of  10Base-T (and its successors) and structured cabling which is still the basis of most

commercial LANs today. In addition, fiber-optic cabling is increasingly used in commercial applications.

As cabling is not always possible, wireless Wi-Fi is now the most common technology in residential

premises, as the cabling required is minimal and it is well suited to mobile laptops and smartphones.

Technical aspects

Network topology describes the layout pattern of interconnections between devices and networksegments. Switched Ethernet has been for some time the most common Data Link Layer and Physical

Layer implementation for local area networks. At the higher layers, the Internet Protocol (TCP/IP) has

become the standard. Smaller LANs generally consist of one or more switches linked to each other,

often at least one is connected to a router, cable modem, or ADSL modem for Internet access.Larger

LANs are characterized by their use of redundant links with switches using the  spanning tree protocol to

prevent loops, their ability to manage differing traffic types via quality of service (QoS), and to segregate

traffic with VLANs. Larger LANs also contain a wide variety of network devices such as switches,

firewalls, routers, load balancers, and sensors.LANs may have connections with other LANs via leased

lines, leased services, or by tunneling across the Internet using virtual private network technologies.

Depending on how the connections are established and secured in a LAN, and the distance involved, aLAN may also be classified as a metropolitan area network (MAN) or a wide area network (WAN)

Design options

WANs are used to connect LANs and other types of networks together, so that users and computers in

one location can communicate with users and computers in other locations. Many WANs are built for

one particular organization and are private. Others, built by Internet service providers, provide

connections from an organization's LAN to the Internet. WANs are often built using  leased lines. At each

end of the leased line, a router connects the LAN on one side with a second router within the LAN on the

other. Leased lines can be very expensive. Instead of using leased lines, WANs can also be built using less

costly circuit switching or packet switching methods. Network protocols including TCP/IP deliver

transport and addressing functions. Protocols including Packet over SONET/SDH, MPLS, ATM and Frame

relay are often used by service providers to deliver the links that are used in WANs. X.25 was an

important early WAN protocol, and is often considered to be the "grandfather" of Frame Relay as many

of the underlying protocols and functions of  X.25 are still in use today (with upgrades) by Frame Relay.

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Academic research into wide area networks can be broken down into three areas:  mathematical

models, network emulation and network simulation. 

Performance improvements are sometimes delivered via wide area file services or WAN optimization. 

Connection technology options

Several options are available for WAN connectivity:

Option: Description Advantages Disadvantages Bandwidth protocols

Leased

line 

Point-to-Point connection between

two computers or Local Area

Networks (LANs)

Most secure Expensive

PPP, 

HDLC, 

SDLC, 

HNAS 

Circuit

switching

A dedicated circuit path is createdbetween end points. Best example

is dialup connections

Less Expensive Call Setup28 - 144

kbit/sPPP, ISDN 

Packet

switching

Devices transport packets via a

shared single point-to-point or

point-to-multipoint link across a

carrier internetwork. Variable

length packets are transmitted over

Permanent Virtual Circuits (PVC) or

Switched Virtual Circuits (SVC) 

Shared media

across link

X.25 

Frame-

Relay 

Cell relay

Similar to packet switching, but

uses fixed length cells instead of 

variable length packets. Data is

divided into fixed-length cells and

then transported across virtual

circuits

Best for

simultaneous

use of voice and

data

Overhead can be

considerableATM

Transmission rates usually range from 1200 bit/s to 24 Mbit/s, although some connections such as ATM

and Leased lines can reach speeds greater than 156 Mbit/s. Typical communication links used in WANs

are telephone lines, microwave links & satellite channels.Recently with the proliferation of low cost of 

Internet connectivity many companies and organizations have turned to VPN to interconnect their

networks, creating a WAN in that way. Companies such as Cisco, New Edge Networks and Check Point 

offer solutions to create VPN networks.

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A virtual private network 

(VPN) is a network that uses primarily public telecommunication infrastructure, such as the Internet, to

provide remote offices or traveling users access to a central organizational network.VPNs typically

require remote users of the network to be authenticated, and often secure data with encryption

technologies to prevent disclosure of private information to unauthorized parties.VPNs may serve anynetwork functionality that is found on any network, such as sharing of data and access to network

resources, printers, databases, websites, etc. A VPN user typically experiences the central network in a

manner that is identical to being connected directly to the central network. VPN technology via the

public Internet has replaced the need to requisition and maintain expensive dedicated leased-line

telecommunication circuits once

History

Until the end of the 1990s, networked computers were connected through expensive leased lines 

and/or dial-up phone lines.Virtual Private Networks reduce network costs because they avoid a need for

physical leased lines that individually connect remote offices (or remote users) to a private Intranet 

(internal network). Users can exchange private data securely, making the expensive leased lines

unnecessary.Different VPN systems can include a lot of variation, such as:

The protocols they use to tunnel the traffic

The tunnel's termination point, i.e., customer edge or network provider edge

Whether they offer site-to-site or remote access connectivity

The levels of security provided

The OSI layer they present to the connecting network, such as Layer 2 circuits or Layer 3 network

connectivity

Some classification schemes are discussed in the following sections. VPN technology used in 1990. VPN

stands for virtual private network. There are two protocols in use in VPN:

Transparent mode

used in remote technology

Tunnel mode

used in local network

Security mechanisms

Secure VPNs use cryptographic tunneling protocols to provide confidentiality by blocking intercepts and

packet sniffing, allowing sender authentication to block identity spoofing, and provide message integrity 

by preventing message alteration.

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Secure VPN protocols include the following:

IPsec (Internet Protocol Security) was developed by the Internet Engineering Task Force (IETF), and was

initially developed for IPv6, which requires it. This standards-based security protocol is also widely used

with IPv4. Layer 2 Tunneling Protocol frequently runs over IPsec. Its design meet the most security goals-

authentication, integrity, and confidentiality. IPsec functions by summarizing an IP packet in conjunctionwith a surrounding packet, and encrypting the outcome.

Transport Layer Security (SSL/TLS) can tunnel an entire network's traffic, as it does in the OpenVPN 

project, or secure an individual connection. A number of vendors provide remote access VPN capabilities

through SSL. An SSL VPN can connect from locations where IPsec runs into trouble with Network

Address Translation and firewall rules.

Datagram Transport Layer Security (DTLS), is used in Cisco's next-generation VPN product, Cisco

AnyConnect VPN, to solve the issues SSL/TLS has with tunneling over UDP.

Microsoft Point-to-Point Encryption (MPPE) works with their Point-to-Point Tunneling Protocol and inseveral compatible implementations on other platforms.

Microsoft introduced Secure Socket Tunneling Protocol (SSTP) in Windows Server 2008 and Windows

Vista Service Pack 1. SSTP tunnels Point-to-Point Protocol (PPP) or Layer 2 Tunneling Protocol traffic

through an SSL 3.0 channel.

MPVPN (Multi Path Virtual Private Network). Ragula Systems Development Company owns the

registered trademark "MPVPN".[2] 

Secure Shell (SSH) VPN -- OpenSSH offers VPN tunneling to secure remote connections to a network or

inter-network links. This should not be confused with port forwarding. OpenSSH server provides alimited number of concurrent tunnels and the VPN feature itself does not support personal

authentication.[3][4][5] 

[edit] Authentication

Tunnel endpoints must authenticate before secure VPN tunnels can be established.

User-created remote access VPNs may use passwords, biometrics, two-factor authentication or other

cryptographic methods.

Network-to-network tunnels often use passwords or digital certificates, as they permanently store thekey to allow the tunnel to establish automatically and without intervention from the user.

[edit] Routing

Tunneling protocols can be used in a point-to-point topology that would theoretically not be considered

a VPN, because a VPN by definition is expected to support arbitrary and changing sets of network nodes.

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But since most router implementations support a software-defined tunnel interface, customer-

provisioned VPNs often are simply defined tunnels running conventional routing protocols.

[edit] PPVPN Building blocks

Depending on whether the PPVPN runs in layer 2 or layer 3, the building blocks described below may be

L2 only, L3 only, or combine them both. Multiprotocol Label Switching (MPLS) functionality blurs the L2-

L3 identity.

RFC 4026 generalized the following terms to cover L2 and L3 VPNs, but they were introduced in RFC

2547.[6] 

Customer edge device. (CE)

A device at the customer premises, that provides access to the PPVPN. Sometimes it's just a

demarcation point between provider and customer responsibility. Other providers allow customers to

configure it.

Provider edge device (PE)

A PE is a device, or set of devices, at the edge of the provider network, that presents the provider's view

of the customer site. PEs are aware of the VPNs that connect through them, and maintain VPN state.

Provider device (P)

A P device operates inside the provider's core network, and does not directly interface to any customer

endpoint. It might, for example, provide routing for many provider-operated tunnels that belong to

different customers' PPVPNs. While the P device is a key part of implementing PPVPNs, it is not itself 

VPN-aware and does not maintain VPN state. Its principal role is allowing the service provider to scale its

PPVPN offerings, as, for example, by acting as an aggregation point for multiple PEs. P-to-P connections,

in such a role, often are high-capacity optical links between major locations of provider.

[edit] User-visible PPVPN services

This section deals with the types of VPN considered in the IETF; some historical names were replaced by

these terms.

[edit] OSI Layer 1 services

[edit] Virtual private wire and private line services (VPWS and VPLS)

In both of these services, the service provider does not offer a full routed or bridged network, but

provides components to build customer-administered networks. VPWS are point-to-point while VPLS

can be point-to-multipoint. They can be Layer 1 emulated circuits with no data link structure.

The customer determines the overall customer VPN service, which also can involve routing, bridging, or

host network elements.

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An unfortunate acronym confusion can occur between Virtual Private Line Service and Virtual Private

LAN Service; the context should make it clear whether "VPLS" means the layer 1 virtual private line or

the layer 2 virtual private LAN.

[edit] OSI Layer 2 services

Virtual LAN

A Layer 2 technique that allows for the coexistence of multiple LAN broadcast domains, interconnected

via trunks using the IEEE 802.1Q  trunking protocol. Other trunking protocols have been used but have

become obsolete, including Inter-Switch Link (ISL), IEEE 802.10 (originally a security protocol but a

subset was introduced for trunking), and ATM LAN Emulation (LANE).

Virtual private LAN service (VPLS)

Developed by IEEE, VLANs allow multiple tagged LANs to share common trunking. VLANs frequently

comprise only customer-owned facilities. The former[clarification needed] is a layer 1 technology that

supports emulation of both point-to-point and point-to-multipoint topologies. The method discussed

here extends Layer 2 technologies such as 802.1d and 802.1q LAN trunking to run over transports such

as Metro Ethernet. 

As used in this context, a VPLS is a Layer 2 PPVPN, rather than a private line, emulating the full

functionality of a traditional local area network (LAN). From a user standpoint, a VPLS makes it possible

to interconnect several LAN segments over a packet-switched, or optical, provider core; a core

transparent to the user, making the remote LAN segments behave as one single LAN.[7] 

In a VPLS, the provider network emulates a learning bridge, which optionally may include VLAN service.

Pseudo wire (PW)

PW is similar to VPWS, but it can provide different L2 protocols at both ends. Typically, its interface is a

WAN protocol such as Asynchronous Transfer Mode or Frame Relay. In contrast, when aiming to provide

the appearance of a LAN contiguous between two or more locations, the Virtual Private LAN service or

IPLS would be appropriate.

IP-only LAN-like service (IPLS)

A subset of VPLS, the CE devices must have L3 capabilities; the IPLS presents packets rather than frames.

It may support IPv4 or IPv6.

[edit] OSI Layer 3 PPVPN architectures

This section discusses the main architectures for PPVPNs, one where the PE disambiguates duplicate

addresses in a single routing instance, and the other, virtual router, in which the PE contains a virtual

router instance per VPN. The former approach, and its variants, have gained the most attention.

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One of the challenges of PPVPNs involves different customers using the same address space, especially

the IPv4 private address space.[8] The provider must be able to disambiguate overlapping addresses in

the multiple customers' PPVPNs.

BGP/MPLS PPVPN

In the method defined by RFC 2547, BGP extensions advertise routes in the IPv4 VPN address family,

which are of the form of 12-byte strings, beginning with an 8-byte Route Distinguisher (RD) and ending

with a 4-byte IPv4 address. RDs disambiguate otherwise duplicate addresses in the same PE.

PEs understand the topology of each VPN, which are interconnected with MPLS tunnels, either directly

or via P routers. In MPLS terminology, the P routers are Label Switch Routers without awareness of 

VPNs.

Virtual router PPVPN

The Virtual Router architecture,[9][10] as opposed to BGP/MPLS techniques, requires no modification to

existing routing protocols such as BGP. By the provisioning of logically independent routing domains, the

customer operating a VPN is completely responsible for the address space. In the various MPLS tunnels,

the different PPVPNs are disambiguated by their label, but do not need routing distinguishers.

Virtual router architectures do not need to disambiguate addresses, because rather than a PE router

having awareness of all the PPVPNs, the PE contains multiple virtual router instances, which belong to

one and only one VPN.

[edit] Plaintext tunnels

Main article: Tunneling protocol 

Some virtual networks may not use encryption to protect the data contents. While VPNs often provide

security, an unencrypted overlay network does not neatly fit within the secure or trusted categorization.

For example a tunnel set up between two hosts that used Generic Routing Encapsulation (GRE) would in

fact be a virtual private network, but neither secure nor trusted.

Besides the GRE example above, native plaintext tunneling protocols include Layer 2 Tunneling Protocol

(L2TP) when it is set up without IPsec and Point-to-Point Tunneling Protocol (PPTP) or Microsoft Point-

to-Point Encryption (MPPE). 

[edit] Trusted delivery networks

Trusted VPNs do not use cryptographic tunneling, and instead rely on the security of a single provider's

network to protect the traffic.

Multi-Protocol Label Switching (MPLS) is often used to overlay VPNs, often with quality-of-service

control over a trusted delivery network.

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Layer 2 Tunneling Protocol (L2TP)[11] which is a standards-based replacement, and a compromise taking

the good features from each, for two proprietary VPN protocols: Cisco's Layer 2 Forwarding (L2F)[12] 

(obsolete as of 2009[update]) and Microsoft's Point-to-Point Tunneling Protocol (PPTP).[13] 

From the security standpoint, VPNs either trust the underlying delivery network, or must enforce

security with mechanisms in the VPN itself. Unless the trusted delivery network runs among physicallysecure sites only, both trusted and secure models need an authentication mechanism for users to gain

access to the VPN.

[edit] VPNs in mobile environments

Main article: Mobile virtual private network 

Mobile VPNs are used in a setting where an endpoint of the VPN is not fixed to a single IP address, but

instead roams across various networks such as data networks from cellular carriers or between multiple

Wi-Fi access points.[14] Mobile VPNs have been widely used in public safety, where they give law

enforcement officers access to mission-critical applications, such as computer-assisted dispatch andcriminal databases, while they travel between different subnets of a mobile network.[15] They are also

used in field service management and by healthcare organizations,[16] among other industries.

Increasingly, mobile VPNs are being adopted by mobile professionals and white-collar workers who

need reliable connections.[16] They are used for roaming seamlessly across networks and in and out of 

wireless-coverage areas without losing application sessions or dropping the secure VPN session. A

conventional VPN cannot survive such events because the network tunnel is disrupted, causing

applications to disconnect, time out,[14] or fail, or even cause the computing device itself to crash.[16] 

Instead of logically tying the endpoint of the network tunnel to the physical IP address, each tunnel is

bound to a permanently associated IP address at the device. The mobile VPN software handles the

necessary network authentication and maintains the network sessions in a manner transparent to the

application and the user.[14] The Host Identity Protocol (HIP), under study by the Internet Engineering

Task Force, is designed to support mobility of hosts by separating the role of  IP addresses for host

identification from their locator functionality in an IP network. With HIP a mobile host maintains its

logical connections established via the host identity identifier while associating with different IP

addresses when roaming between access networks.

Simple Network Management Protocol (SNMP) is an "Internet-standard protocol for managing devices

on IP networks. Devices that typically support SNMP include routers, switches, servers, workstations,

printers, modem racks, and more.”[1] It is used mostly in network management systems to monitor network-attached devices for conditions that warrant administrative attention. SNMP is a component of 

the Internet Protocol Suite as defined by the Internet Engineering Task Force (IETF). It consists of a set of 

standards for network management, including an application layer protocol, a database schema, and a

set of  data objects.[2] 

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SNMP exposes management data in the form of variables on the managed systems, which describe the

system configuration. These variables can then be queried (and sometimes set) by managing

applications.

Protocol details

SNMP operates in the Application Layer of the Internet Protocol Suite (Layer 7 of the OSI model). The

SNMP agent receives requests on UDP port 161. The manager may send requests from any available

source port to port 161 in the agent. The agent response will be sent back to the source port on the

manager. The manager receives notifications (Traps and InformRequests) on port 162. The agent may

generate notifications from any available port.

SNMPv1 specifies five core protocol data units (PDUs). Two other PDUs, GetBulkRequest and

InformRequest were added in SNMPv2 and carried over to SNMPv3.

All SNMP PDUs are constructed as follows:

IP

header

UDP

headerversion community

PDU-

type

request-

id

error-

status

error-

index

variable

bindings

The seven SNMP protocol data units (PDUs) are as follows:

[edit] GetRequest

A manager-to-agent request to retrieve the value of a variable or list of variables. Desired variables are

specified in variable bindings (values are not used). Retrieval of the specified variable values is to be

done as an atomic operation by the agent. A Response with current values is returned.

[edit] SetRequest

A manager-to-agent request to change the value of a variable or list of variables. Variable bindings are

specified in the body of the request. Changes to all specified variables are to be made as an atomic

operation by the agent. A Response with (current) new values for the variables is returned.

[edit] GetNextRequest

A manager-to-agent request to discover available variables and their values. Returns a Response with

variable binding for the lexicographically next variable in the MIB. The entire MIB of an agent can be

walked by iterative application of GetNextRequest starting at OID 0. Rows of a table can be read by

specifying column OIDs in the variable bindings of the request.

[edit] GetBulkRequest

Optimized version of GetNextRequest. A manager-to-agent request for multiple iterations of 

GetNextRequest. Returns a Response with multiple variable bindings walked from the variable binding

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or bindings in the request. PDU specific non-repeaters and max-repetitions fields are used to control

response behavior. GetBulkRequest was introduced in SNMPv2.

[edit] Response

Returns variable bindings and acknowledgement from agent to manager for GetRequest, SetRequest,

GetNextRequest, GetBulkRequest and InformRequest. Error reporting is provided by error-status and

error-index fields. Although it was used as a response to both gets and sets, this PDU was called

GetResponse in SNMPv1.

[edit] Trap

Asynchronous notification from agent to manager. Includes current sysUpTime value, an OID identifying

the type of trap and optional variable bindings. Destination addressing for traps is determined in an

application-specific manner typically through trap configuration variables in the MIB. The format of the

trap message was changed in SNMPv2 and the PDU was renamed SNMPv2-Trap.

[edit] InformRequest

Acknowledged asynchronous notification from manager to manager. This PDU uses the same format as

the SNMPv2 version of Trap. Manager-to-manager notifications were already possible in SNMPv1 (using

a Trap), but as SNMP commonly runs over UDP where delivery is not assured and dropped packets are

not reported, delivery of a Trap was not guaranteed. InformRequest fixes this by sending back an

acknowledgement on receipt. Receiver replies with Response parroting all information in the

InformRequest. This PDU was introduced in SNMPv2.

A virtual local area network, virtual LAN or VLAN, is a group of hosts with a common set of requirements

that communicate as if they were attached to the same broadcast domain, regardless of their physicallocation. A VLAN has the same attributes as a physical local area network (LAN), but it allows for end

stations to be grouped together even if they are not located on the same network switch. VLAN

membership can be configured through software instead of physically relocating devices or connections.

To physically replicate the functions of a VLAN, it would be necessary to install a separate, parallel

collection of network cables and equipment which are kept separate from the primary network.

However unlike a physically separate network, VLANs must share bandwidth; two separate one-gigabit

VLANs using a single one-gigabit interconnection can suffer both reduced throughput and congestion. It

virtualizes VLAN behaviors (configuring switch ports, tagging frames when entering VLAN, lookup MAC

table to switch/flood frames to trunk links, and untagging when exit from VLAN.)

Cisco VLAN Trunking Protocol (VTP)

Main article: VLAN Trunking Protocol 

On Cisco Devices, VTP (VLAN Trunking Protocol) maintains VLAN configuration consistency across the

entire network. VTP uses Layer 2 trunk frames to manage the addition, deletion, and renaming of VLANs

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on a network-wide basis from a centralized switch in the VTP server mode. VTP is responsible for

synchronizing VLAN information within a VTP domain and reduces the need to configure the same VLAN

information on each switch.

VTP minimizes the possible configuration inconsistencies that arise when changes are made. These

inconsistencies can result in security violations, because VLANs can cross connect when duplicate namesare used. They also could become internally disconnected when they are mapped from one LAN type to

another, for example, Ethernet to ATM LANE ELANs or FDDI 802.10 VLANs. VTP provides a mapping

scheme that enables seamless trunking within a network employing mixed-media technologies.

VTP provides the following benefits:

VLAN configuration consistency across the network

Mapping scheme that allows a VLAN to be trunked over mixed media

Accurate tracking and monitoring of VLANs

Dynamic reporting of added VLANs across the network

Plug-and-play configuration when adding new VLANs

As beneficial as VTP can be, it does have disadvantages that are normally related to the spanning tree

protocol (STP) as a bridging loop propagating throughout the network can occur. Cisco switches run an

instance of STP for each VLAN, and since VTP propagates VLANs across the campus LAN, VTP effectively

creates more opportunities for a bridging loop to occur.

Before creating VLANs on the switch that will be propagated via VTP, a VTP domain must first be set up.

A VTP domain for a network is a set of all contiguously trunked switches with the same VTP domain

name. All switches in the same management domain share their VLAN information with each other, and

a switch can participate in only one VTP management domain. Switches in different domains do not

share VTP information.

Using VTP, each Catalyst Family Switch advertises the following on its trunk ports:

Management domain

Configuration revision number

Known VLANs and their specific parameters

In computer networking, a wireless access point (WAP) is a device that allows wireless devices to

connect to a wired network using Wi-Fi, Bluetooth or related standards. The WAP usually connects to a

router (via a wired network), and can relay data between the wireless devices (such as computers or

printers) and wired devices on the network.

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Industrial grade WAPs are rugged, with a metal cover and a DIN rail mount. During operations they can

tolerate a wider temperature range, high humidity and exposure to water, dust, and oil. Wireless

security includes: WPA-PSK, WPA2, IEEE 802.1x/RADIUS, WDS, WEP, TKIP, and CCMP (AES) encryption.

Unlike some home consumer models, industrial wireless access points can also act as a bridge, router, or

a client.

Wireless access point vs. ad hoc network

Some people confuse Wireless Access Points with Wireless Ad Hoc networks. An Ad Hoc network uses a

connection between two or more devices without using a wireless access point: the devices

communicate directly when in range. An Ad Hoc network is used in situations such as a quick data

exchange or a multiplayer LAN game because setup is easy and does not require an access point. Due to

its peer-to-peer layout, Ad Hoc connections are similar to Bluetooth ones and are generally not

recommended for a permanent installation.

Internet access via Ad Hoc networks, using features like Windows' Internet Connection Sharing, may

work well with a small number of devices that are close to each other, but Ad Hoc networks don't scale

well. Internet traffic will converge to the nodes with direct internet connection, potentially congesting

these nodes. For internet-enabled nodes, Access Points have a clear advantage, with the possibility of 

having multiple access points connected by a wired LAN. 

[edit] Limitations

One IEEE 802.11 WAP can typically communicate with 30 client systems located within a radius of 

103 m.[citation needed] However, the actual range of communication can vary significantly, depending

on such variables as indoor or outdoor placement, height above ground, nearby obstructions, other

electronic devices that might actively interfere with the signal by broadcasting on the same frequency,type of  antenna, the current weather, operating radio frequency, and the power output of devices.

Network designers can extend the range of WAPs through the use of  repeaters and reflectors, which can

bounce or amplify radio signals that ordinarily would go un-received. In experimental conditions,

wireless networking has operated over distances of several hundred kilometers.[1] 

Most jurisdictions have only a limited number of frequencies legally available for use by wireless

networks. Usually, adjacent WAPs will use different frequencies (Channels) to communicate with their

clients in order to avoid interference between the two nearby systems. Wireless devices can "listen" for

data traffic on other frequencies, and can rapidly switch from one frequency to another to achieve

better reception. However, the limited number of frequencies becomes problematic in crowded

downtown areas with tall buildings using multiple WAPs. In such an environment, signal overlap

becomes an issue causing interference, which results in signal droppage and data errors.

Wireless networking lags behind wired networking in terms of increasing bandwidth and throughput. 

While (as of 2010) typical wireless devices for the consumer market can reach speeds of 300 Mbit/s

(megabits per second) (IEEE 802.11n) or 54 Mbit/s (IEEE 802.11g), wired hardware of similar cost

reaches 1000 Mbit/s (Gigabit Ethernet). One impediment to increasing the speed of wireless

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communications comes from Wi-Fi's use of a shared communications medium, so a WAP is only able to

use somewhat less than half the actual over-the-air rate for data throughput. Thus a typical 54 MBit/s

wireless connection actually carries TCP/IP data at 20 to 25 Mbit/s. Users of legacy wired networks

expect faster speeds, and people using wireless connections keenly want to see the wireless networks

catch up.

By 2008 draft 802.11n based access points and client devices have already taken a fair share of the

market place but with inherent problems integrating products from different vendors.

[edit] Security

Main article: Wireless LAN Security 

Wireless access has special security considerations. Many wired networks base the security on physical

access control, trusting all the users on the local network, but if wireless access points are connected to

the network, anyone on the street or in the neighboring office could connect.

The most common solution is wireless traffic encryption. Modern access points come with built-in

encryption. The first generation encryption scheme WEP proved easy to crack; the second and third

generation schemes, WPA and WPA2, are considered secure if a strong enough password or passphrase 

is used.

Some WAPs support hotspot style authentication using RADIUS and other authentication servers. 

A wireless repeater is a computer networking device which acts as a repeater between a wireless router 

and computers. Typical use of a wireless repeater is to add one when your computer is too far away

from any of the buildings' other wireless access points. If set up properly it will then extend the range of 

the local wireless network. The open source firmware DD-WRT enables home network routers tofunction as wireless repeaters. These have also been called wireless expanders, depending on culture

and country.

Gigabit Ethernet (GbE or 1 GigE) is a term describing various technologies for transmitting Ethernet

frames at a rate of a gigabit per second (1,000,000,000 bits per second), as defined by the IEEE 802.3-

2008 standard. It came into use beginning in 1999, gradually supplanting Fast Ethernet in wired local

networks where it performed considerably faster. The cables and equipment are very similar to previous

standards, and as of 2011 are very common and economical.

Half-duplex gigabit links connected through hubs are allowed by the specification but in the marketplace

full-duplex with switches is normal.

A network switch or switching hub is a computer networking device that connects network segments. 

The term commonly refers to a multi-port network bridge that processes and routes data at the data

link layer (layer 2) of the OSI model. Switches that additionally process data at the network layer (Layer

3) and above are often referred to as Layer 3 switches or multilayer switches. 

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Function

The network switch plays an integral part in most modern Ethernet local area networks (LANs). Mid-to-

large sized LANs contain a number of linked managed switches. Small office/home office (SOHO)

applications typically use a single switch, or an all-purpose converged device such as a gateway to access

small office/home broadband services such as DSL or cable internet. In most of these cases, the end-user device contains a router and components that interface to the particular physical broadband

technology. User devices may also include a telephone interface for VoIP. 

An Ethernet switch operates at the data link layer of the OSI model to create a separate collision domain 

for each switch port. With 4 computers (e.g., A, B, C, and D) on 4 switch ports, A and B can transfer data

back and forth, while C and D also do so simultaneously, and the two conversations will not interfere

with one another. In the case of a hub, they would all share the bandwidth and run in half duplex, 

resulting in collisions, which would then necessitate retransmissions. Using a switch is called

microsegmentation. This allows computers to have dedicated bandwidth on a point-to-point

connections to the network and to therefore run in full duplex without collisions.

[edit] Role of switches in networks

Switches may operate at one or more layers of the OSI model, including data link, network, or transport

(i.e., end-to-end). A device that operates simultaneously at more than one of these layers is known as a

multilayer switch. 

In switches intended for commercial use, built-in or modular interfaces make it possible to connect

different types of networks, including Ethernet, Fibre Channel, ATM, ITU-T G.hn and 802.11. This

connectivity can be at any of the layers mentioned. While Layer 2 functionality is adequate for

bandwidth-shifting within one technology, interconnecting technologies such as Ethernet and token ring are easier at Layer 3.

Interconnection of different Layer 3 networks is done by routers. If there are any features that

characterize "Layer-3 switches" as opposed to general-purpose routers, it tends to be that they are

optimized, in larger switches, for high-density Ethernet connectivity.

In some service provider and other environments where there is a need for a great deal of analysis of 

network performance and security, switches may be connected between WAN routers as places for

analytic modules. Some vendors provide firewall,[2][3] network intrusion detection,[4] and performance

analysis modules that can plug into switch ports. Some of these functions may be on combined

modules.[5] 

In other cases, the switch is used to create a mirror image of data that can go to an external device.

Since most switch port mirroring provides only one mirrored stream, network hubs can be useful for

fanning out data to several read-only analyzers, such as intrusion detection systems and packet sniffers. 

[edit] Layer-specific functionality

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Main article: Multilayer switch 

A modular network switch with three network modules (a total of 24 Ethernet and 14 Fast Ethernet

ports) and one power supply.

While switches may learn about topologies at many layers, and forward at one or more layers, they do

tend to have common features. Other than for high-performance applications, modern commercial

switches use primarily Ethernet interfaces, which can have different input and output bandwidths of 10,

100, 1000 or 10,000 megabits per second. 

At any layer, a modern switch may implement power over Ethernet (PoE), which avoids the need for

attached devices, such as an VoIP phone or wireless access point, to have a separate power supply.

Since switches can have redundant power circuits connected to uninterruptible power supplies, the

connected device can continue operating even when regular office power fails.

[edit] Layer 1 hubs versus higher-layer switches

A network hub, or repeater, is a simple network device. Hubs do not manage any of the traffic that

comes through them. Any packet entering a port is broadcast out or "repeated" on every other port,

except for the port of entry. Since every packet is repeated on every other port, packet  collisions affect

the entire network, limiting its capacity.

There are specialized applications where a hub can be useful, such as copying traffic to multiple network

sensors. High end switches have a feature which does the same thing called  port mirroring. 

By the early 2000s, there was little price difference between a hub and a low-end switch.[6] 

[edit] Layer 2

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A network bridge, operating at the data link layer, may interconnect a small number of devices in a

home or the office. This is a trivial case of bridging, in which the bridge learns the MAC address of each

connected device.

Single bridges also can provide extremely high performance in specialized applications such as storage

area networks. 

Classic bridges may also interconnect using a spanning tree protocol that disables links so that the

resulting local area network is a tree without loops. In contrast to routers, spanning tree bridges must

have topologies with only one active path between two points. The older IEEE 802.1D spanning tree

protocol could be quite slow, with forwarding stopping for 30 seconds while the spanning tree would

reconverge. A Rapid Spanning Tree Protocol was introduced as IEEE 802.1w, but the newest edition of 

IEEE 802.1D adopts the 802.1w extensions as the base standard.

The IETF is specifying the TRILL protocol, which is the application of link-state routing technology to the

layer-2 bridging problem. Devices which implement TRILL, called RBridges, combine the best features of 

both routers and bridges.

While "layer 2 switch" remains more of a marketing term than a technical term,[citation needed] the

products that were introduced as "switches" tended to use microsegmentation and Full duplex to

prevent collisions among devices connected to Ethernet. By using an internal forwarding plane much

faster than any interface, they give the impression of simultaneous paths among multiple devices.

Once a bridge learns the topology through a spanning tree protocol, it forwards data link layer frames

using a layer 2 forwarding method. There are four forwarding methods a bridge can use, of which the

second through fourth method were performance-increasing methods when used on "switch" products

with the same input and output port bandwidths:

Store and forward: The switch buffers and verifies each frame before forwarding it.

Cut through: The switch reads only up to the frame's hardware address before starting to forward it.

Cut-through switches have to fall back to store and forward if the outgoing port is busy at the time the

packet arrives. There is no error checking with this method.

Fragment free: A method that attempts to retain the benefits of both store and forward and cut

through. Fragment free checks the first 64 bytes of the frame, where addressing information is stored.

According to Ethernet specifications, collisions should be detected during the first 64 bytes of the frame,

so frames that are in error because of a collision will not be forwarded. This way the frame will alwaysreach its intended destination. Error checking of the actual data in the packet is left for the end device.

Adaptive switching: A method of automatically selecting between the other three modes.

While there are specialized applications, such as storage area networks, where the input and output

interfaces are the same bandwidth, this is rarely the case in general LAN applications. In LANs, a switch

used for end user access typically concentrates lower bandwidth (e.g., 10/100 Mbit/s) into a higher

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bandwidth (at least 1 Gbit/s). Alternatively, a switch that provides access to server ports usually

connects to them at a much higher bandwidth than is used by end user devices.

[edit] Layer 3

Within the confines of the Ethernet physical layer, a layer 3 switch can perform some or all of the

functions normally performed by a router. The most common layer-3 capability is awareness of  IP

multicast through IGMP snooping. With this awareness, a layer-3 switch can increase efficiency by

delivering the traffic of a multicast group only to ports where the attached device has signaled that it

wants to listen to that group.

[edit] Layer 4

While the exact meaning of the term Layer-4 switch is vendor-dependent, it almost always starts with a

capability for network address translation, but then adds some type of  load distribution based on TCP 

sessions.[7] 

The device may include a stateful firewall, a VPN concentrator, or be an IPSec security gateway.

[edit] Layer 7

Layer 7 switches may distribute loads based on URL or by some installation-specific technique to

recognize application-level transactions. A Layer-7 switch may include a web cache and participate in a

content delivery network.[8] 

The Internet Protocol Suite is the set of  communications protocols used for the Internet and other

similar networks. It is commonly also known as TCP/IP named from two of the most important protocols

in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were the first two

networking protocols defined in this standard. Modern IP networking represents a synthesis of several

developments that began to evolve in the 1960s and 1970s, namely the precursors of the Internet and

local area networks, which emerged during the 1980s, together with the advent of the World Wide Web 

in the early 1990s.

The Internet Protocol Suite classifies its methods and protocols into four hierarchical abstraction layers.

From the lowest to the highest communication layer, these are the Link Layer, the Internet Layer, the

Transport Layer, and the Application Layer.[1][2] The layers define the operational scope or reach of the

protocols in each layer, reflected loosely in the layer names. Each layer has functionality that solves a set

of problems relevant in its scope.

The Link Layer contains communication technologies for the local network to which the host is

connected directly by hardware components. This is called the link. It provides the basic connectivity

functions interacting with the networking hardware of the computer and the associated management of 

interface-to-interface messaging. The Internet Layer provides communication methods between

multiple links of a computer and facilitates the interconnection of networks. As such, this layer

establishes the Internet. It contains primarily the Internet Protocol, which defines the fundamental

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addressing namespaces, Internet Protocol Version 4 (IPv4) and Internet Protocol Version 6 (IPv6) used to

identify and locate hosts on the network. Host-to-host communication tasks are handled in the

Transport Layer, which provides a general application-agnostic framework to transmit data between

hosts using protocols like the Transmission Control Protocol and the User Datagram Protocol (UDP).

Finally, the highest-level Application Layer contains all protocols that are defined each specifically for

the functioning of the vast array of data communications services. This layer handles application-based

interaction, with recognition of application-specific data formats, on a process-to-process level between

communicating Internet hosts

Internet Protocol Suite

Application Layer

BGP · DHCP · DNS · FTP · HTTP · IMAP · IRC · LDAP ·

MGCP · NNTP · NTP · POP · RIP · RPC · RTP · SIP ·SMTP · SNMP · SOCKS · SSH · Telnet · TLS/SSL ·

XMPP · (more) 

Transport Layer

TCP · UDP · DCCP · SCTP · RSVP · ECN · (more) 

Internet Layer

IP (IPv4, IPv6) · ICMP · ICMPv6 · IGMP · IPsec ·

(more) 

Link Layer

ARP/InARP · NDP · OSPF · Tunnels (L2TP) · PPP ·

Media Access Control (Ethernet, DSL, ISDN, FDDI) 

Border Gateway Protocol

From Wikipedia, the free encyclopedia

(Redirected from BGP) 

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Jump to: navigation, search 

"BGP" redirects here. For the Formula One Team, see Brawn GP. 

The Border Gateway Protocol (BGP) is the protocol backing the core routing decisions on the  Internet. It

maintains a table of IP networks or 'prefixes' which designate network reachability among autonomous

systems (AS). It is described as a path vector protocol. BGP does not use traditional Interior Gateway

Protocol (IGP) metrics, but makes routing decisions based on path, network policies and/or rulesets. For

this reason, it is more appropriately termed a reachability protocol rather than routing protocol. 

BGP was created to replace the Exterior Gateway Protocol (EGP) protocol to allow fully decentralized

routing in order to transition from the core ARPAnet model to a decentralized system that included the

NSFNET backbone and its associated regional networks. This allowed the Internet to become a truly

decentralized system. Since 1994, version four of the BGP has been in use on the Internet. All previous

versions are now obsolete. The major enhancement in version 4 was support of  Classless Inter-Domain

Routing and use of  route aggregation to decrease the size of  routing tables. Since January 2006, version

4 is codified in RFC 4271, which went through more than 20 drafts based on the earlier RFC 1771 version

4. RFC 4271 version corrected a number of errors, clarified ambiguities and brought the RFC much closer

to industry practices.

Most Internet service providers must use BGP to establish routing between one another (especially if 

they are multihomed). Therefore, even though most Internet users do not use it directly, BGP is one of 

the most important protocols of the Internet. Compare this with Signaling System 7 (SS7), which is the

inter-provider core call setup protocol on the PSTN. Very large private IP networks use BGP internally.

An example would be the joining of a number of large OSPF (Open Shortest Path First) networks where

OSPF by itself would not scale to size. Another reason to use BGP is multihoming a network for better

redundancy either to multiple access points of a single ISP (RFC 1998) or to multiple ISPs.

Open Shortest Path First

From Wikipedia, the free encyclopedia

(Redirected from OSPF) 

Jump to: navigation, search 

Open Shortest Path First (OSPF) is an adaptive routing protocol for Internet Protocol (IP) networks. It

uses a link state routing algorithm and falls into the group of interior routing protocols, operating within

a single autonomous system (AS). It is defined as OSPF Version 2 in RFC 2328 (1998) for IPv4.[1] The

updates for IPv6 are specified as OSPF Version 3 in RFC 5340 (2008).[2] Research into the convergence

time of OSPF can be found in Stability Issues in OSPF Routing (2001).[3] 

OSPF is perhaps the most widely-used interior gateway protocol (IGP) in large enterprise networks. IS-IS, 

another link-state routing protocol, is more common in large service provider networks. The most

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widely-used exterior gateway protocol is the Border Gateway Protocol (BGP), the principal routing

protocol between autonomous systems on the Internet.