Flow Models

A computer network is comprised of nodes corresponding to network elements such as workstations,routers and switches and links that connect those elements. A network now contains all the traffic originating at a node and destined for some other node in the network. Each how can in principle traverse a set of paths connecting its origin and destination, which is determined by the routing policy.

In computer networks, the low traffic is carried on packets, whose payload is expressed in bytes, while on road networks, the traffic is carried on vehicles. The volume of traffic measured on a link may refer to either the number of packets and/or the number of bytes in computer networks, and such data for a particular time interval -typically of the order of a couple of minutes- are available through queries using the Simple Network Management Protocol (SNMP) protocol.

 The volume of traffic on a 1link is the sum of volumes of all rows traversing that link. This produces highly aggregate data and the question of interest is to estimate various statistics of the underlying network.

Simple Network Management Protocol - SNMP

Simple Network Management Protocol (SNMP) is a widely used protocol designed to facilitate the management of networked devices from a central location.  Designed originally for the management of devices such as routers and switches, its usage has grown rapidly to encompass the monitoring of nearly any electronic device one can think of.  SNMP is now  used to monitor and manage television broadcast studios, automated fare collection systems, airborne military platforms, energy distribution systems, emergency radio networks, and much more.

The SNMP architecture is composed of three major elements:

• Managers (software) are responsible for communicating with (and managing) network devices that implement SNMP Agents (also software).
• Agents reside in devices such as workstations, switches, routers, microwave radios, printers, and provide information to Managers.
• MIBs (Management Information Base) describe data objects to be managed by an Agent within a device. MIBs are actually just text files, and values of MIB data objects are the topic of conversation between Managers and Agents.

SNMP Standards and Versions:
SNMP Standards are described in Request for Comments (RFC) documents published by the Internet Engineering Task Force (IETF).  Standards Topics can generally be categorized into:

• Messaging protocols between Managers and Agents (which encompasses security issues)
• MIB syntax standards
• “Standard MIB” definitions