CISA 4 and 5

A series of documents that can be used to aid the implmenetation of a framework for IT service management (ITSM)

A partial release, contains only those items that have undergone changes since the last release

• Problem management's objective is to reduce the number and severity of incidents
• Incident management's objective is to return the effected business process back to its normal state as quickly as possible

Verify that system changes are authorized, tested, and implemented in a controlled manner prior to being introduced into the production environment

The planning and monitoring of computing and network resources to ensure that the available resources are used efficiently and effectively

• Parents and children
• 1:N mappings between records
• A child may have one parent

• Basic data modeling construct is a set
• A set is formed by an owner, a member, and a name
• A member can have a role in one or more sets
• An owner can be a member or owner of another set
• A set is usually 1:N but can be 1:1
• Complex, hard to query

• Data and relationships are tables
• A table is rows (tuples or records) and columns
• Rows have the same columns
• Columns (domains or attributes) have fields
• Values are atomic
• Each row is unique
• Each column name is unique
• Sequences of rows and columns don't matter

• The elimination of redundant data
• Objective is to minimize the amount of information, quicker queries, better integrity

• A given instance of a data object has one and only one value for each attribute
• Attributes represent elementary data
• Each row consists of a primary key that ids some entity 
• A foreign key has a null value or an existing value link to another table (referential integrity)

• Dedicated - symmetric telecom lines connecting 2 locations, permanently connected
• Switch - not permanent, setup on demand

• Circuit switching - like a phone
• Packet switching

• Baseband - one channel available, entire capacity used to transmit, moves in one direction
• Broadband - different frequencies, full-duplex

• All People Seem To Need Data Protocols
• Application
• Presentation
• Session
• Transport
• Network
• Data Link
• Physical

Provides a standard interface for applications that must communicate with devices on the network

• Transforms data to provide a standard interface for the app layer
• Provides common communication services (encryption, text compression and reformatting)
• Converts outgoing data into a format acceptable to the network layer and passes to session layer
• Incoming data is rec from session layer and converted to a format acceptable by the app layer

• Controls the dialogs (sessions) between computers 
• All conversations, data exchanges, and dialogs between app layers are managed by session layer

• Provides reliable and transparent transfer of data between end-points
• End to end error recovery and flow control
• Ensures all data sent by session layer are received by remote system's transport layer
• Acknowledges info received from remote transport layer for every packet sent

• Creates a virtual circuit between the local and remote transport layers
• Understands IP addresses
• Prepares packets for data link layer by converting to frames
• Converts receiving frames to packets

• Provides for reliable transfer of data across physical link
• Receives packets of data from network layer, encapsulates them into frames and sends as bit streams to physical layer
• Error detection through Cyclic redundancy check for each frame
• MAC addresses

Provides the hardware that transmits and receives bit streams

• Application
• Transport
• Network Interface
• LAN/WAN Interface

• Application - Application, Presentation, Session
• Transport - Transport
• Network interface - Network
• LAN Interface - Data link, Physical

• Private path for each connection
• No collisions
• Each device can only see its traffic

• Physical
• Extend the range of a network, or connect two network segments

Signal is distorted or reduced

• Physical
• Serve as the center of a star network
• Can be active, repeat signals
• Passive, split signals

• Data link
• Connects or creates two separate LANs
• Reduces collision domains
• Two segments below data link, one above that layer
• Software based

• Data link
• Divide and interconnect network segments
• Reduce collision domains
• More functionality than bridges 
• Hardware based

• Network
• Link two or more physically separate networks
• Segments remain logically separate 
• Examine IP addresses
• Generally software based and not as efficient as switches 
• Examine every packet

• Network/Transport
• Like a router at layer 3
• Compares destination IP to list and calcs best route (virtual circuit created)
• Uses hardware

• Group of devices on one or more logically segmented LANs.
• Set up by configuring ports on a switch, so that devices attached communicate as if they were attached to the same physical network segment

• Application layer
• Protocol converters

• Simplex - one way flow
• Half-duplex - one way at a time
• Full-duplex - both ways at one time

• Synchronous - bits are transmitted w/o interruption at a constant speed. Char used to indicate start of data block
• Asynchronous - beginning and end of transmission marked with a byte each

• Physical layer
• When a physical circuit has more bandwidth capacity than required by an individual signal.
• Allocates portions of bandwidth

• Time-division multiplexing - allocation based on preassigned time slots, doesn't matter if there is data to transmit
• Asynchronous time division - allocate as needed, dynamically assigned slots
• Frequency division - allocate based on the frequency of traffic
• Statistical - allocated dynamically to any data channel w/ info to transmit

• Data link layer
• Provides a single, pre-established communication path to remote network 
• Standard for transmitting IP over serial lines

• Lower three layers of OSI (Network, Data link, physical)
• Packet switched WAN protocol suite
• Telecom standard that defines how connections between data terminal equipment and data communications or circuit terminating equipment are maintained for remote terminal access

• Data link protocol
• Uses standard encapsulation technique to handle multiple virtual circuits between connected devices
• Encapsulation method, high-level data link control
• More efficient than X.25
• Relies more on upper layer protocols for error handling
• Low cost

• Tunnel mode - encrypts the entire packet, including header
• Transport mode - encrypts only the data portion

• TCP/IP based protocol
• Monitors and controls different variables throughout the network

• The acceptable data loss in case of disruption
• Earliest point in time which it is acceptable to recover data
• Amount of data that can be lost, e.g. four hours then data backed up every four hours
• Higher RPO = longer time without data

• Determined based on the acceptable downtime in case of a disruption
• Earliest point in time at which operations must resume
• Lower time = higher costs

Level of service to be reached during the alternate process mode until normal operations are restored

Designated to receive the information about every incident

• Main mission is to develop the needed steps to maintain a similar level of information and IT resource security as was in place at primary site.
• Responsible for security of org assets

Responsible for obtaining, packaging and shipping media and records to the recovery facilities

Responsible for coordinating the process of moving from the hot site to a new location or the restored original

• Executed at the host level by software on the host and target. 
• Synchronous - data not written to the primary until backup sends confirmation
• Asynchronous - data transferred with some delay

• Incremental - the data that was changed is backed up
• Differential - full files and folders are backed up, what has changed

To negotiate, document and manage the services in the manner in which the customer requires those services

• Critical functions - cannot be performed unless replaced by identical capabilities, cannot be replaced by manual methods
• Vital - can be preformed manually for a short time
• Sensitive - can be preformed manually at a tolerable cost for an extended time
• Noncritical - can be interrupted for an extended period of time at little or no cost, little time to restore