Glossary

	Why Multi-tier? Native XML Storage

I want to many thanks to my best friend Alper for his help.

IP Datagram - The basic unit of information for Internet transmission.

ISP - Internet Service Provider; a service provider that offers Internet and Web access to customers.

Jitter - A measure of the variation in delay (latency, or
response time). Especially key for Voice and streaming
services.

LAN - Local Area Network; a relatively small computer
network, usually confined to a building or campus.

Latency - The delay for traffic crossing a network, caused by queuing and switching delays in each device on the path.by queuing and switching delays in each device on the path.

LDAP - Lightweight Directory Access Protocol; a standard for accessing information directories.

Log file - A file listing all of the events that have occurred.

Load-balancing - Distributing network and system
activity and processing evenly across resources so that no one server or device is overloaded.

Mean Time Between Failures - The average time
interval between failures of the same type. For instance, the MTBF of the backbone is 1,000 hours; the MTBF of any router is 5,000 hours.

Mean Time to Repair - The average time it takes to
restore service after a specific type of failure has occurred. For example, the MTTR for a router is 15 minutes.

Metrics - Measurements that are used to assess service quality. They may be direct (such as latency) or calculated (transactions / second).

MIB - Management Information Base; a database of
information on a resource such as what can be known about it and what can be done to it. For example, the MIB for a server contains information on its CPU, operating system, memory and disk.

MPLS - Multi-Protocol Label Switching; the successor to DiffServ, a label will be applied to a service flow and will cause bandwidth reservation and prioritization with a set of hop-by-hop behaviours negotiated among the relay devices.

MSP - Management Service Provider; a service provider that delivers managed network, system and/or application technologies across a network to multiple customers.

NSP - Network Service Provider; a service provider that offers network connectivity and a range of managed network technologies to multiple customers.

N-tier Architecture - A multi-tiered approach to system management. An n-tier architecture assigns sub-units of the transaction to sets of servers, meaning that any number of servers can be involved in a transaction.

Packet Loss - A basic measure of network reliability, an acceptable loss rate for a given application - time-critical services are more impacted with packet losses.

PING ("ping") - An ICMP (Internet Control Message
Protocol) message that solicits a response. Used for
measuring delay and testing connectivity and basic
operation of a remote node.

Policy (Policies) - Embedded rules that control the
management system, such as policies for allocating
bandwidth to specific applications.

Policy Enforcement - Management agents act as the
enforcement points for policies. They carry out the policy rules and report to the remote management center.

Policy Management - Allows administrators to create, modify, and track the policies they are using to manage their e-businesses. These typically have "fill in the blank" policy templates, as well as mechanisms for storing and protecting policy information.

Policy Servers - Act as the central repository for policy information and distribute it to the appropriate
management agents. Management agents can use a "pull" operation with LDAP, or the server can use a "push" operation if COPS is used for the exchange of policy information.

Propagation Delay - The time it takes for a packet to
travel from one switching element to the next.

Proxy - A system operating on behalf of another entity.
For example, an SNMP proxy translates between SNMP and another management protocol. A proxy server is used to mirror content.

Public Key Encryption - A technique that uses two
encryption keys. Each communicating party has a "private" key for decrypting messages and a "public" key that is easily available to anyone. Thus, anyone can use the public key to encrypt a message, but only the private key holder can decrypt it. This is a simpler and more scalable system than having every pair of partners maintain its own keys.

QoS - Quality of Service; a measure of the delivered
service quality. It is measured by one or more metrics.

Queuing - A method of storing packets and forwarding
them in a different order. This allows higher-priority traffic to move through first. Queuing also handles temporary bursts of traffic.

Queuing Delay - The delay that occurs while packets
wait in a device before being forwarded.

Rate Control - A method that reduces network
congestion by controlling the rate at which traffic is
introduced. It reduces the probability of dropping packets when congestion actually occurs.

Redirection - A technique that assigns a new connection to the "best" site. The DNS Server assigns an address based on minimum network delays, site loads, or other criteria.

Response Time - A measure of the round-trip delay - for a packet or a transaction such as downloading a Web page.

Rules - Rules drive the policy systems. For example: "if server utilization exceeds X%, send an alert and bring a standby server on-line." An e-Business-oriented rule might be: "if the number of abandoned shopping carts exceeds X% over 10 minutes, send

Server Farm - A collection of servers dedicated to the
same tasks. Multiple servers increase transaction flow and provide higher fault-tolerance.

Service Provider - An organization that offers services to other businesses. There is a range of service providers including: Incumbent Local Exchange Carriers (ILECs), Competitive Local Exchange Carriers (CLECs), Internet Service Providers (ISPs), and Management Service Providers (MSPs), among others.