Information about my New Blog Page (Nifty Financial Market)

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Fabric Extender Technology (FEX) in Nexus

Fabric Extender, the term marketed by Cisco, is basically a port extender as it is referenced in the developing IEEE 802.1Qbh (Bridge Port Extension). The 802.1Qbh standard is specific to control protocol used between the controlling bridge and the port extender, as it is referred in the draft. Supporting standards, also currently being developed like IEEE 802.1Qbg (Edge Virtual Bridging)  and IEEE 802.1Qbc

The Fabric Extender Architecture

The components involved:

Controlling Bridge (Parent Switch) to provide the control and management plane functions. This could be one or two Nexus 5000 or Nexus 7000 switches.
Port Extender which provides the physical port termination. This would be the Nexus 2000 series.
Connecting the FEX to the controlling bridge is done using SFPs over Ethernet fiber.
Encapsulation mechanism to transport frames from the FEX to the controlling bridge.
Control protocols to manage/monitor the FEXs

Cisco calls the encapsulation mechanism used on between the FEX and controlling bridge VN-Tag (previously VN-link). Controlling bridge is IEEE terminology, whereas parent switch is Cisco terminology. The IEEE 802.1Qbh working group was initiated by Cisco in a hope to standardize their VN-Tag technology. VN-Tag provides the capability to differentiate traffic between different host interfaces traversing the fabric uplinks. 

VN- Tag Header

The Fabric Extender Forwarding

A FEX or a Nexus 2000 operate as a remote linecard, but does not support local switching, all forwarding is performed on the parent switch. This is in contrast to most modular switches like the DFCs on Catalyst 6500. One of the reasons this was done was re-usability. By offloading the forwarding and intelligent decisions, the idea Cisco had in mind is that by upgrading the parent switch, the FEX being deployed in larger numbers can remain. Where the DFC on a Catalyst 6500 lives on the line card, the equivalent processing lives on the parent switch, be it the Nexus 7000/5000. Thus upgrading the parent switch upgrades that FEX capability since all it does is encapsulate traffic for identification. In large deployments where the cost of hundreds of FEXs out ways the cost of the Nexus 5000s used, this makes perfect sense. In very small deployments, this reason becomes arguable.

The Fabric Extender Management

It was briefly mentioned before that a parent switch and all its FEXs are treated as a single management device. This is accomplished by a small satellite image running on the FEX. This image is a smaller compatible version of the parent NX-OS image pushed from the parent switch. The parent switch is responsible for this and happens with no user involvement. Same applies to when the parent switch is upgraded, every attached FEX is upgraded during this time too.

The Fabric Extender Operation

Lets take a deep look at the backend operations. There are various interfaces involved:

1. HIF (Host Interface): Are the physical user/host interfaces on the FEX. These interfaces receive normal Ethernet traffic before it is encapsulated with the VN-Tag header. Each HIF interface is assigned a unique VN-Tag ID that is used with the encapsulation.

2. NIF (Network Interface): Physical uplink interfaces on the FEX. These interfaces can only connect back to the parent switch and carries only VN-Tagged traffic.

3. LIF (Logical Interface): Is the logical interface representation of the HIF and its configuration on the parent switch. Forwarding decisions are based on the LIF.

4. VIF (Virtual Interface): Is a logical interface on the FEX. The parent switch assigns/pushes the config of a LIF to the VIF of an associated FEX which is mapped to a physical HIF. This is why replacing a FEX becomes trivial in that the broken FEX is unplugged and the replacement is plugged in.

Nexus Switches Overview

Cisco Nexus Family of products has become extremely popular in small and large data centers thanks to their ability of unifying storage, data and networking services.
Also the Cisco Fabric Interconnect can provide a rock-solid programmable platform that fully supports any virtualized environment.

The Cisco Nexus family includes a generous number of different Nexus models to meet the demands of any Data Center environment.

Nexus Family Switch

Cisco Nexus Family consists of following series types

1) CISCO NEXUS 9000 SERIES SWITCHES
The Data Center switches of Nexus 9000 can operate in Cisco NX-OS Software or Application Centric Infrastructure (ACI) modes.
The main features of the new Cisco Nexus 9000 Series are: support of Fabric Extender Technology (FEX), virtual Port Channel (VPC) and Virtual Extensible LAN (VXLAN).

Nexus 9K Switches

2) CISCO NEXUS 7000 SERIES SWITCHES

The Data Center switches of 7K Nexus can provide an end-to-end data center architecture on a single platform, including data center core, aggregation, and access layer. The 7k series provides high-density 10, 40, and 100 Gigabit Ethernet interfaces. The main features of the Cisco Nexus 7000 Series are support for FEX, Virtual Port Channel (VPC), VDC, MPLS and Fabricpath. In addition, the N7K supports fairly robust and established technologies for multi-DC interconnect (DCI).

Nexus 7K Switches

3) CISCO NEXUS 5000 SERIES SWITCHES
The Data Center switches of 5K provides access layer (End of Row), providing architectural support for virtualization and Unified Fabric environments. Cisco Nexus 5000 Series can support VXLAN and comprehensive Layer 2 and 3 features for scaling data center networking. It supports Native Fibre Channel, Ethernet, and FCoE interfaces. The default system software includes most Cisco Nexus 5000 Platform features, such as Layer 2 security and management features. Licensed features include: Layer 3 routing, IP multicast and enhanced Layer 2 (Cisco Fabric Path).

Nexus 5K Switches

4) CISCO NEXUS 3000 SERIES SWITCHES
The product family offers features such as latency of less than a microsecond, line-rate at Layer 2 & 3 unicast, multicast switching, and the support of 40 Gigabit Ethernet interfaces. The Cisco Nexus 3000 Series switches are positioned for use in environments with ultra-low latency requirements such as financial High-Frequency Trading (HFT), High-Performance Computing (HPC) and automotive crash-test simulation Applications.

Nexus 3K Switches

The Cisco Nexus 3000 platform offers more than 15 models to satisfy all the switching needs an organization might have. The Nexus 3000 series offers switches starting with 1GE ports (Nexus 3000) and scales all the way up to 32 port 100GE ports with the Nexus 3232C model. Environments sensitive to delays will surely benefit from this series as they have been designed to practically eliminate any switching latency while at the same time offering large buffer spaces per port.

Cloud Computing Security Threat - IV

Cloud Computing, continuing further to its world of Security Threats

Threat No. 10: Cloud service abuses

Cloud services can be commandeered to support nefarious activities, such as using cloud computing resources to break an encryption key in order to launch an attack. Other examples including launching DDoS attacks, sending spam and phishing emails, and hosting malicious content.

Providers need to recognize types of abuse -- such as scrutinizing traffic to recognize DDoS attacks -- and offer tools for customers to monitor the health of their cloud environments. Customers should make sure providers offer a mechanism for reporting abuse. Although customers may not be direct prey for malicious actions, cloud service abuse can still result in service availability issues and data loss.

Threat No. 11: DoS attacks

DoS attacks have been around for years, but they've gained prominence again thanks to cloud computing because they often affect availability. Systems may slow to a crawl or simply time out. “Experiencing a denial-of-service attack is like being caught in rush-hour traffic gridlock; there is one way to get to your destination and there is nothing you can do about it except sit and wait,” the report said.

DoS attacks consume large amounts of processing power, a bill the customer may ultimately have to pay. While high-volume DDoS attacks are very common, organizations should be aware of asymmetric, application-level DoS attacks, which target Web server and database vulnerabilities.

Cloud providers tend to be better poised to handle DoS attacks than their customers, the CSA said. The key is to have a plan to mitigate the attack before it occurs, so administrators have access to those resources when they need them.

Threat No. 12: Shared technology, shared dangers

Vulnerabilities in shared technology pose a significant threat to cloud computing. Cloud service providers share infrastructure, platforms, and applications, and if a vulnerability arises in any of these layers, it affects everyone. “A single vulnerability or misconfiguration can lead to a compromise across an entire provider’s cloud,” the report said.

If an integral component gets compromised -- say, a hypervisor, a shared platform component, or an application -- it exposes the entire environment to potential compromise and breach. The CSA recommended a defense-in-depth strategy, including multifactor authentication on all hosts, host-based and network-based intrusion detection systems, applying the concept of least privilege, network segmentation, and patching shared resources.

Cloud Computing Security Threats-III

Further we go on for threats for Cloud Computing

Threat No. 7: The APT parasite

The CSA aptly calls advanced persistent threats (APTs) “parasitical” forms of attack. APTs infiltrate systems to establish a foothold, then stealthily exfiltrate data and intellectual property over an extended period of time.

APTs typically move laterally through the network and blend in with normal traffic, so they're difficult to detect. The major cloud providers apply advanced techniques to prevent APTs from infiltrating their infrastructure, but customers need to be as diligent in detecting APT compromises in cloud accounts as they would in on-premises systems.

Common points of entry include spear phishing, direct attacks, USB drives preloaded with malware, and compromised third-party networks. In particular, the CSA recommends training users to recognize phishing techniques.

Regularly reinforced awareness programs keep users alert and less likely to be tricked into letting an APT into the network -- and IT departments need to stay informed of the latest advanced attacks. Advanced security controls, process management, incident response plans, and IT staff training all lead to increased security budgets. Organizations should weigh these costs against the potential economic damage inflicted by successful APT attacks.

Threat No. 8: Permanent data loss

As the cloud has matured, reports of permanent data loss due to provider error have become extremely rare. But malicious hackers have been known to permanently delete cloud data to harm businesses, and cloud data centers are as vulnerable to natural disasters as any facility.

Cloud providers recommend distributing data and applications across multiple zones for added protection. Adequate data backup measures are essential, as well as adhering to best practices in business continuity and disaster recovery. Daily data backup and off-site storage remain important with cloud environments.

The burden of preventing data loss is not all on the cloud service provider. If a customer encrypts data before uploading it to the cloud, then that customer must be careful to protect the encryption key. Once the key is lost, so is the data.

Compliance policies often stipulate how long organizations must retain audit records and other documents. Losing such data may have serious regulatory consequences. The new EU data protection rules also treat data destruction and corruption of personal data as data breaches requiring appropriate notification. Know the rules to avoid getting in trouble.

Threat No. 9: Inadequate diligence

Organizations that embrace the cloud without fully understanding the environment and its associated risks may encounter a “myriad of commercial, financial, technical, legal, and compliance risks,” the CSA warned. Due diligence applies whether the organization is trying to migrate to the cloud or merging (or working) with another company in the cloud. For example, organizations that fail to scrutinize a contract may not be aware of the provider’s liability in case of data loss or breach.

Operational and architectural issues arise if a company's development team lacks familiarity with cloud technologies as apps are deployed to a particular cloud. The CSA reminds organizations they must perform extensive due diligence to understand the risks they assume when they subscribe to each cloud service.

Cloud Computing- Security Threats-II

The shared, on-demand nature of cloud computing introduces the possibility of new security breaches that can erase any gains made by the switch to cloud technology. Cloud services by nature enable users to bypass organization-wide security policies and set up their own accounts in the service of shadow IT project.

Continuing with Security Threats, we further have the following threats that are vulnerable through cloud

Threat No. 4: Exploited system vulnerabilities

System vulnerabilities, or exploitable bugs in programs, are not new, but they've become a bigger problem with the advent of multitenancy in cloud computing. Organizations share memory, databases, and other resources in close proximity to one another, creating new attack surfaces.

Fortunately, attacks on system vulnerabilities can be mitigated with “basic IT processes,” says the CSA. Best practices include regular vulnerability scanning, prompt patch management, and quick follow-up on reported system threats.

According to the CSA, the costs of mitigating system vulnerabilities “are relatively small compared to other IT expenditures.” The expense of putting IT processes in place to discover and repair vulnerabilities is small compared to the potential damage. Regulated industries need to patch as quickly as possible, preferably as part of an automated and recurring process, recommends the CSA. Change control processes that address emergency patching ensure that remediation activities are properly documented and reviewed by technical teams.

Threat No. 5: Account hijacking

Phishing, fraud, and software exploits are still successful, and cloud services add a new dimension to the threat because attackers can eavesdrop on activities, manipulate transactions, and modify data. Attackers may also be able to use the cloud application to launch other attacks.

Common defense-in-depth protection strategies can contain the damage incurred by a breach. Organizations should prohibit the sharing of account credentials between users and services, as well as enable multifactor authentication schemes where available. Accounts, even service accounts, should be monitored so that every transaction can be traced to a human owner. The key is to protect account credentials from being stolen, the CSA says.

Threat No. 6: Malicious insiders

The insider threat has many faces: a current or former employee, a system administrator, a contractor, or a business partner. The malicious agenda ranges from data theft to revenge. In a cloud scenario, a hellbent insider can destroy whole infrastructures or manipulate data. Systems that depend solely on the cloud service provider for security, such as encryption, are at greatest risk.

The CSA recommends that organizations control the encryption process and keys, segregating duties and minimizing access given to users. Effective logging, monitoring, and auditing administrator activities are also critical.

As the CSA notes, it's easy to misconstrue a bungling attempt to perform a routine job as "malicious" insider activity. An example would be an administrator who accidentally copies a sensitive customer database to a publicly accessible server. Proper training and management to prevent such mistakes becomes more critical in the cloud, due to greater potential exposure.

Cloud Computing-Security Threats-I

Top security threats organizations face when using cloud services

Enterprises are no longer sitting on their hands, wondering if they should risk migrating applications and data to the cloud. They're doing it -- but security remains a serious concern.

The first step in minimizing risk in the cloud is to identify the top security threats.

The shared, on-demand nature of cloud computing introduces the possibility of new security breaches that can erase any gains made by the switch to cloud technology, the CSA warned. As noted in previous CSA reports, cloud services by nature enable users to bypass organization-wide security policies and set up their own accounts in the service of shadow IT projects. New controls must be put in place.

Threat No. 1: Data breaches

Cloud environments face many of the same threats as traditional corporate networks, but due to the vast amount of data stored on cloud servers, providers become an attractive target. The severity of potential damage tends to depend on the sensitivity of the data exposed. Exposed personal financial information tends to get the headlines, but breaches involving health information, trade secrets, and intellectual property can be more devastating.

When a data breach occurs, companies may incur fines, or they may face lawsuits or criminal charges. Breach investigations and customer notifications can rack up significant costs. Indirect effects, such as brand damage and loss of business, can impact organizations for years.

Cloud providers typically deploy security controls to protect their environments, but ultimately, organizations are responsible for protecting their own data in the cloud. The CSA has recommended organizations use multifactor authentication and encryption to protect against data breaches.

Threat No. 2: Compromised credentials and broken authentication 

Data breaches and other attacks frequently result from lax authentication, weak passwords, and poor key or certificate management. Organizations often struggle with identity management as they try to allocate permissions appropriate to the user’s job role. More important, they sometimes forget to remove user access when a job function changes or a user leaves the organization.

Multifactor authentication systems such as one-time passwords, phone-based authentication, and smartcards protect cloud services because they make it harder for attackers to log in with stolen passwords. The Anthem breach, which exposed more than 80 million customer records, was the result of stolen user credentials. Anthem had failed to deploy multifactor authentication, so once the attackers obtained the credentials, it was game over.

Many developers make the mistake of embedding credentials and cryptographic keys in source code and leaving them in public-facing repositories such as GitHub. Keys need to be appropriately protected, and a well-secured public key infrastructure is necessary, the CSA said. They also need to be rotated periodically to make it harder for attackers to use keys they’ve obtained without authorization.

Organizations planning to federate identity with a cloud provider need to understand the security measures the provider uses to protect the identity platform. Centralizing identity into a single repository has its risks. Organizations need to weigh the trade-off of the convenience of centralizing identity against the risk of having that repository become an extremely high-value target for attackers.

Threat No. 3: Hacked interfaces and APIs

Practically every cloud service and application now offers APIs. IT teams use interfaces and APIs to manage and interact with cloud services, including those that offer cloud provisioning, management, orchestration, and monitoring.

The security and availability of cloud services -- from authentication and access control to encryption and activity monitoring -- depend on the security of the API. Risk increases with third parties that rely on APIs and build on these interfaces, as organizations may need to expose more services and credentials, the CSA warned. Weak interfaces and APIs expose organizations to security issues related to confidentiality, integrity, availability, and accountability.

APIs and interfaces tend to be the most exposed part of a system because they're usually accessible from the open Internet. The CSA recommends adequate controls as the “first line of defense and detection.” Threat modeling applications and systems, including data flows and architecture/design, become important parts of the development lifecycle. The CSA also recommends security-focused code reviews and rigorous penetration testing.

Cloud Computing

Cloud computing is the delivery of computing services—servers, storage, databases, networking, software, analytics and more—over the Internet (“the cloud”). Companies offering these computing services are called cloud providers and typically charge for cloud computing services based on usage, similar to how you are billed for water or electricity at home. 

Uses of cloud computing

You are probably using cloud computing right now, even if you don’t realise it. If you use an online service to send email, edit documents, watch movies or TV, listen to music, play games or store pictures and other files, it is likely that cloud computing is making it all possible behind the scenes. The first cloud computing services are barely a decade old, but already a variety of organisations—from tiny startups to global corporations, government agencies to non-profits—are embracing the technology for all sorts of reasons. Here are a few of the things you can do with the cloud:

• Create new apps and services
• Store, back up and recover data
• Host websites and blogs
• Stream audio and video
• Deliver software on demand
• Analyse data for patterns and make predictio

Active Directory Overview and its Components

ACTIVE DIRECTORY (OVERVIEW)

Keeping track of everything on your network is a time-consuming task. Even on small networks, users tend to have difficulty finding network file and printer shares. Without some kind of network directory, medium and large networks are impossible to manage, and users will often have a difficult time finding resources on the network.

Previous versions of Microsoft Windows included services to help users and administrators find network resources. Network Neighborhood is useful in many environments, but users often complain about the clumsy interface, and its unpredictability baffles many administrators. The WINS Manager and Server Manager could be used to view a list of systems on the network, but they were not readily available to end users. Administrators utilized User Manager to add and delete users, an entirely different type of network object. These applications got the job done, but proved to be inefficient—especially in large networks.

All of these objects resided in a common container: the Microsoft Windows NT domain. Windows NT domains worked best in small-sized and medium-sized environments. Administrators of large environments were forced to partition their network into multiple domains interconnected with trusts. Microsoft Windows 2000 Server introduces Active Directory to replace domain functionality. Active Directory will continue to get the job done, but in a much more efficient way. Active Directory can be replicated between multiple domain controllers, so no single system is critical. In this way, the crucial data stored within Active Directory is both redundant and load-balanced.

A directory, in the most generic sense, is a comprehensive listing of objects. A phone book is a type of directory that stores information about people, businesses, and government organizations. Phone books typically record names, addresses, and phone numbers. Active Directory is similar to a phone book in several ways, and it is far more flexible. Active Directory will store information about organizations, sites, systems, users, shares, and just about any other network object that you can imagine. Not all objects are as similar to each other as those stored in the phone book, so Active Directory includes the ability to record different types of information about different objects. This chapter will teach you

• What Active Directory is
• How standard protocols like DNS dynamic update protocol and Lightweight Directory Access Protocol (LDAP) are used
• How to plan for migrating to Active Directory
• What objects, schema, object classes, and attributes are
• How replication and partitioning work
• What the global catalog is useful for and how to use it.

Active Directory Components

As I mentioned in the introduction, Active Directory stores information about network components. It allows clients to find objects within its namespace. The term namespace (also known as console tree) refers to the area in which a network component can be located. For example, the table of contents of this book forms a namespace in which chapters can be resolved to page numbers. DNS is a namespace that resolves host names to IP addresses. Telephone books provide a namespace for resolving names to telephone numbers. Active Directory provides a namespace for resolving the names of network objects to the objects themselves. Active Directory can resolve a wide range of objects, including users, systems, and services on a network.

Everything that Active Directory tracks is considered an object. An object is any user, system, resource, or service tracked within Active Directory. The generic term object is used because Active Directory is capable of tracking a variety of items, and many objects can share common attributes.

Attributes describe objects in Active Directory. For example, all User objects share attributes to store a user name, full name, and description. Systems are also objects, but they have a separate set of attributes that include a host name, an IP address, and a location.

The set of attributes available for any particular object type is called a schema. The schema makes object classes different from each other. Schema information is actually stored within Active Directory, which allows administrators to add attributes to object classes and have them distributed across the network to all corners of the domain, without restarting any domain controllers.

A container is a special type of object used to organize Active Directory. It does not represent anything physical, like a user or a system. Instead, it is used to group other objects. Container objects can be nested within other containers.

Each object in an Active Directory has a name. These are not the names that you are accustomed to, like "Tony" or "Eric." They are LDAP distinguished names. LDAP distinguished names are complicated, but they allow any object within a directory to be identified uniquely regardless of its type. 

The term tree is used to describe a set of objects within Active Directory. When containers and objects are combined hierarchically, they tend to form branches—hence the term. A related term is contiguous subtree, which refers to an unbroken branch of the tree.

Continuing the tree metaphor, the term forest describes trees that are not part of the same namespace but that share a common schema, configuration, and global catalog. Trees in a forest all trust each other, so objects in these trees are available to all users if the security allows it. Organizations that are divided into multiple domains should group the trees into a single forest.

A site is a geographical location, as defined within Active Directory. Sites correspond to logical IP subnets, and as such, they can be used by applications to locate the closest server on a network. Using site information from Active Directory can profoundly reduce the traffic on wide area networks.

SNMP Management Systems and Agent

SNMP Management Systems and Agents

SNMP locates the network management component on one or more computers and locates the managed component on multiple managed devices:

• SNMP manager. An SNMP manager, also known as an SNMP management system or a management console, is any computer that sends queries for IP-related information to a managed computer, known as an SNMP agent. In some cases, the SNMP manager can send a request to an SNMP agent to change a configuration value.
• SNMP agent. An SNMP agent is any computer or other network device that monitors and responds to queries from SNMP managers. The agent can also send a trap message to the manager when specified events, such as a system reboot or illegal access, occur.

A computer on which you install SNMP management software is an SNMP manager, and a computer on which you install agent software, such as the Microsoft SNMP agent included with Windows Server 2003, is an SNMP agent. The SNMP manager displays the information it receives in a user-friendly graphical user interface. You configure SNMP options, including traps, on the SNMP agent, but the SNMP agent does not display the managed information that it sends to an SNMP manager. For more information about SNMP requests and trap messages, see “SNMP Messages” later in this section.

To enable SNMP communications between an SNMP manager and SNMP agents, you configure the SNMP manager and the SNMP agents that it manages as members of an SNMP community. The community name functions like a password to authenticate communications between the SNMP manager and agent. The SNMP community is an SNMP-defined group, not a group defined in the Active Directory directory service. For more information about SNMP communities, see “SNMP Communities” later in this section.

An SNMP manager can request the following types of information from the SNMP agents that it monitors:

• Network protocol identification and statistics
• Dynamic identification (discovery) of devices attached to the network
• Hardware and software configuration data
• Device performance and usage statistics
• Device error and event messages
• Program and application usage statistics

If you assign the SNMP manager write permission for the SNMP agent, the SNMP manager can also send a configuration request to the agent (using a Set message) to change a local parameter. However, Set requests are limited to a small set of client parameters that have read-write access defined. Most client parameters allow only read-only access.

Understanding the Management Information Base (MIB)

When an SNMP manager requests information from an SNMP agent, the SNMP agent retrieves the current value of the requested information from the Management Information Base (MIB). The MIB defines the managed objects that an SNMP manager monitors (or sometimes configures) on an SNMP agent.

Each system in a network (workstation, server, router, bridge, and so forth) maintains a MIB that reflects the status of the managed resources on that system, such as the version of the software running on the device, the IP address assigned to a port or interface, the amount of free hard drive space, or the number of open files. The MIB does not contain static data, but is instead an object-oriented, dynamic database that provides a logical collection of managed object definitions. The MIB defines the data type of each managed object and describes the object.

The MIB Tree

The SNMP-related branches of the MIB tree are located in the internet branch, which contains two main types of branches:

• Public branches (mgmt=2), which are defined by the Internet Engineering Task Force (IETF) RFCs, are the same for all SNMP-managed devices.
• Private branches (private=4), which are assigned by the Internet Assigned Numbers Authority (IANA), are defined by the companies and organizations to which these branches are assigned.

The following figure shows the structure of the SNMP MIB tree. There are no limits on the width and depth of the MIB tree.

Immediately beneath the root of the MIB tree, International Organization for Standardization (iso), is the Organization (org) branch, followed by Department of Defense (dod), and then Internet (internet). Management (mgmt), the main public branch, defines network management parameters common to devices from all vendors. Underneath the Management branch is MIB-II (mib-2), and beneath this are branches for common management functions such as system management, printers, host resources, and interfaces.

The private branch of the MIB tree contains branches for large organizations, organized under the enterprises branch. Each organization has a root branch node under this object. Each organization creates its own subset of MIB branches and objects, which must comply with a common definition of SNMP information known as Structure of Management Information (SMI). SMI defines the allowed data types for MIB objects.

MIB Objects

At the programmatic level, the definition of each MIB object that an SNMP agent manages includes the following elements:

• The object name and object identifier (also known as an OID).
• A text description of the object.
• The object’s data-type definition (such as counter, string, gauge, or address).
• The index for objects that are assigned complex data types. The index specifies the key field for the table — that is, the field that can be used to identify a row.
  
  The only complex SNMP data type that is allowed is a table, and tables cannot be nested. Examples include the list of a system’s network interfaces, a routing table, or the Address Resolution Protocol (ARP) table.
• The level of access to the object (such as read or read/write) that is allowed.
• Size restrictions.
• Range information.

SNMP references each MIB variable by using its unique object identifier, which identifies the location of a given managed object within the MIB namespace. The object identifier reflects the object’s position within the hierarchy of the MIB tree, containing a sequence of subidentifiers that begin at the root of the MIB tree and end at the object (leaf node). Subidentifiers are separated with a period.

To reference a MIB object, you can use either numeric or text subidentifiers. For example, the following text-based object identifier is interchangeable with its numeric counterpart, shown beneath it. The value of this object identifier, in either format, identifies the current operational state of a network adapter.

Interacting with MIB Objects

To understand how SNMP interacts with MIB objects, you must first understand that the SNMP agent consists of a master agent and one or more subagents, also known as extension agents, which are the dynamic link libraries (DLLs) that SNMP uses to process a request received from an SNMP manager.

When the SNMP service starts, it loads each SNMP extension agent that is listed in the registry. When the master agent receives a request from the SNMP manager, it passes the request to an extension agent, which accesses the appropriate MIB and returns the current value of the relevant MIB object to the SNMP master agent. The SNMP agent then returns the information to the SNMP manager. An SNMP agent can also send unsolicited MIB information to the SNMP manager in response to an event that has been defined as an SNMP trap (unexpected event). In some cases, the SNMP agent changes (or sets) the value of the MIB object.

For example, in order to assess the network load at a particular point in your network, you can use SNMP to retrieve the value of a counter that tracks the number of packets sent over a link to the SNMP agent. Or you might use SNMP to retrieve the value that represents the amount of disk space available for storage. Although SNMP is used less commonly to set the value of a MIB object, to ensure that a link is not used, you might use SNMP to set the link state value of a MIB object to a disabled state.

Compiling a New or Updated MIB File by Using Mibcc.exe

As explained earlier, the SNMP-related branches of the MIB tree are located in the internet branch of the tree. The internet branch contains public branches that are defined by the IETF and private branches that are defined by large organizations. When an organization creates its own subset of MIB branches and objects, or updates an existing MIB file, the new or updated MIB file must be created in compliance with SMI-prescribed data types.

If your organization adds or updates a new MIB file, use the Mibcc.exe tool to compile the MIB file so that the SNMP Management API (Mgmtapi.dll) can use the MIB objects in the new or updated MIB file. After you compile the MIB file, you can reference objects by their text object identifiers instead of their numeric object identifiers. The ASN.1 language is used to define the formats of the protocol data units (PDUs) that are exchanged by SNMP entities and to define the objects that are managed through SNMP. Mibcc.exe converts the ASN.1 MIB description into the binary Mib.bin file, which the Management API then uses to map text-based object names to numeric object identifiers.

You can find Mibcc.exe in the C:\Program Files\Resource Kit folder when you install the Windows Server 2003 Resource Kit companion CD. The Mib.bin file is located in systemroot on Windows Server 2003

SNMP And its Working

Simple Network Management Protocol

Use Simple Network Management Protocol (SNMP) management software to monitor any network device configured with SNMP agent software. The SNMP agent, which is an optional component of Windows Server 2003, interacts with third-party SNMP management software to enable the flow of network status information between monitored devices and applications and the management systems that monitor them.

You can use SNMP in environments that include large networks with hundreds or thousands of nodes that would otherwise be difficult and costly to monitor. SNMP allows monitoring of network devices such as servers, workstations, printers, routers, bridges, and hubs, as well as services such as Dynamic Host Configuration Protocol (DHCP) or Windows Internet Name Service (WINS).

SNMP Architecture

To perform its monitoring services, SNMP uses a distributed architecture of management systems and agents and several related components. Windows Server 2003 provides an SNMP agent that is designed to be capable of interacting with any SNMP manager. The following components are the building blocks of SNMP and the Windows Server 2003 SNMP agent:

• SNMP management systems and agents
• Management Information Base (MIB)
• SNMP Messages
• SNMP Communities
• The communication process between SNMP managers and agents 
• 

The internal architecture of the Windows Server 2003 implementation of SNMP is divided into management and agent functions, which, in some cases, overlap. The following figure illustrates how the Windows Server 2003 SNMP structure fits into the layers of the underlying TCP/IP protocol architecture.

Where is Proxy Server used??

Where is a Proxy server used?

Proxy servers are used for several purposes. If it is used as a caching web proxy, it can dramatically improve performance of a web response. When a request is made by a client, a caching proxy returns response directly from its cache if the document already exists. Otherwise, it makes the request to the real server, returns the result, and save it in its cache for later use.

Proxy servers are also used as "web proxies" to filter web page contents. An organization or company may use a proxy server to block offensive web contents from viewed by the users. Considering the growing need within organizations to prevent employees from accessing specific websites, such as facebook.com, proxy servers are being deployed across the computers connected to the intranet. Some web proxies are able to reformat web pages to suit a specific set of audience, or cater certain organizational or personal internet usage purposes. Further, web proxies can be used to prevent the attack of computer viruses and malware, as well as other hostile content transferred across the internet web pages. However, users can also use web proxy servers to access those blocked sites indirectly. These web proxies are built with PHP or CGI to implement the proxying functionality, and provide web access to those sites blocked by corporation and school proxies. Moreover, Internet Service providers (ISPs) may also use proxies to block computer viruses and other offensive contents.

There are several advantages of Proxy servers. We intend to provide some of the most basic uses of proxy servers.

Performance Improvement:

Proxy servers also contribute to improved web performance since the results of the user requests are saved in cache memory for a set period of time. This is achieved with the help of a caching proxy server, which could save a large amount of time while catering to the requests from a vast user load. A caching proxy server maintains a local copy of frequently requested web content. Hence, it can accelerate service requests by retrieving content from the cache memory, if it had already been requested by another client on the same network. This feature contributes to a significant reduction in upstream bandwidth usage and costs for large organizations with thousands of employees.

Monitoring and Filtering User Requests:

As discussed earlier, web proxies can be used to filter user requests, and block certain content or web pages from being accessed. This can be achieved with the help of a content-filtering web proxy server that differentiates the users’ level of control over the content, based on the user type - Guest or Administrator.

Content-filtering proxies are generally used in organizations and educational institutions with strict internet-usage policies. Blocking certain websites, and restricting access to specific key words and censoring undesirable content are some of the basic features provided by content-filtering or web-filtering proxies. However, there are certain web proxies that are used to bypass geo-restrictions and censorship regulations by using certain advanced services that help access resources from blacklisted web locations.

Anonymous Browsing:

An anonymous proxy server is another type of web proxy that anonymizes users' online activities. This type of proxy server directs the user requests to a destination server, which ultimately has no knowledge of the source of the request. Only the proxy is aware of the source of the request, including the user IP address and location.

Advertisements targeting specific geographical regions Web Proxies can also be used to validate and verify geo-targeted advertisements. Servers of such ads validate the source IP address of the user request, and determine the geographic location of the request with the help of a geo-IP database. The user requests are responded via proxy servers that are located within the respective geographical location, to ensure that advertisements displayed are purely relevant to the users’ location.

Translation:

Considering the global audiences, translation proxies have been developed to localize/translate the content of a source website into a local language of the client computer. Responses for requests sent by local users are replaced with translated content from the source website, and passed back through the proxy server. Some translation proxies also provide additional services such as excluding source content or substituting source content with original local content.

Conclusion

The most popular proxy server used today is a Web Proxy, and it is used to filter contents and allow anonymous browsing. Being able to unblock geo-restricted content is also a wide used application for using public web proxies. Although proxies provide anonymous browsing and content filtering, they are mostly limited to web browsing and also lack security. For secure and encrypted communication with privacy protection, we recommend VPN solution.