All about wireless networking and NMS/EMS

SNMPv1 :  Five operations/PDU: GET-RESPONSE, GET-NEXT, GET-request, SET, TRAP. Security: Community based. (No authentication no privacy) SNMP Community strings are not encrypted(clear-text) in v1 & v2c. Community string will be easily identified by packet sniffer. SNMPv2c :  Two new operations/PDU – GET-BULK(efficient retrieval of multiple OIDs), informs (trap + ACK mech.), plus 64-bit object support. Security: Community based. (No authentication no privacy) SNMP Community strings are not encrypted(clear-text) in v1 & v2c. Community string will be easily identified by packet sniffer.   SNMP v3: PDUs: Includes all the v1&v2c  pdu's. Security: New architecture including security functionality; authentication (SHA, MD5), privacy (encryption - DES, 3DES, AES). Uses Authentication(MD5 or SHA). Encryption using CBC-DES(Adds DES 56-Bit Encryption in Addition to Authentication Based on DES-56).

Management Information Base (MIB): •         A MIB is a collection of “managed objects” which contain information. •        A MIB defines the variables that reside in a managed node,Defined according to SMI (Structure of Management information) rules,Each managed object is described using an object identifier defined in the SMI. •        MIB I: 114 standard objects, Objects included are considered essential for either fault or configuration management. •        MIB II: 185 objects defined •        Other standard MIB Some Common MIB’s interface MIB(RFC 1907), interface MIB(RFC2233), IP MIB(RFC4293), TCP MIB(4022). MIBs – Object Identifiers:               Each managed object within a MIB has a unique object identifier.  SNMP uses these object identifiers to identify the MIB variables to retrieve or modify.  Objects that are in the public domain are described in MIBs introduced in Request for Comments (RFCs).

In network management,  Trap   is a message sent by agent to manager. Two broad categories of traps are generic and  specific , cold start and warm start being the  generic  traps. Here is the difference between two: Cold Start:  This trap indicates that sending device is re-initializing itself such that the agent’s configuration may be altered. Generic trap 0 - coldstart Issued whenever the SNMP agent is re-initializing. Configuration data has changed. Warm Start : This trap indicates that sending device is re-initializing itself such that the agent’s configuration is not altered. Generic trap 1 - warmstart Issued whenever the SNMP agent is re-initializing. Configuration data might change. Note that cold start & warm start traps have nothing to do with self reboot or hard reboot of network element. Only difference between the two is the change in agent’s configuration with cold start trap.

A Network Manager’s job is to get data from Network Elements and present it to the administrators or operators. There are two ways of doing this activity:  1) Polling and 2) Trap . Here is a quick difference between the two: Polling  : A traditional way of providing operators with the network elements information. It’s characteristics are as follows: ·        Pull Mechanism – Requests and get information from network elements at periodic intervals. The periodic interval is most often configurable. ·        Provides non-real time information. It may happen that some changes happen in network element but polling happens an hour after that. Thus, operator gets to know about the changes after an hour. ·        Higher bandwidth needed. Traps  : When an alarm situation exists a trap can be generated, or if some changes happen at network element, an attribute value change event can be generated by the agent. It’s characteristic are as follows: ·        Push Mechanism – E

SNMP Manager: Responsible to communicate with SNMP agent implemented network devices. S NMP Manager’s key functions 1)    Queries agents 2)    Gets responses from agents 3)    Sets variables in agents 4)    Acknowledges asynchronous events from agents SNMP agent: A program packaged with NE. Enabling the agent allows it to collect the management informantion database(MIB) from the device locally and makes it available to the SNMP manager. SNMP agent’s key functions 1             1)    Collects management information about its local environment 2             2)    Stores and retrieves management information as defined in the MIB. 3             3)    Signals an event to the manager. 4             4)    Acts as a proxy for some non–SNMP manageable network node.           Ex: SNMP Agent=Net-SNMP

Every network engineer should know how packets are routed in network. Its a very simple question asked in every interview. IP Packet Delivery on a Local Area Network is a fundamental concept, all system and network administrators should have a clear understanding of. How do computers decide to where to send the packets to?  Should they send them directly to the target computers or the gateway, or both?  The answer is simple. Computers use their local ROUTING table to make that determination.  Yes, even computers have a routing table.  Actually, if a network host is using TCP/IP to communicate on the network, it will have a routing table. Command to check the route info on computer is route PRINT Here is an example of a routing table taken from a computer with an IP address of 192.168.0.1. If you read through this routing table, you will notice that if a packet's network destination address is anything other than an a

An SNMP-managed network consists of three key components:   1)     Managed device   2)     Agent — software which runs on managed devices   3)     Network management station (NMS) — software which runs on the manager 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. When used with  Transport Layer Security  or  Datagram Transport Layer Security  requests are received on port 10161 and traps are sent to port 10162. •       UDP port 161 used for polling •       UDP port 162 used for receiving trap/notifications from managed devices. •        Every device that implements SNMP must use these port numbers as the defaults, but some vendors allow you to change the defa

Channels that wont overlap for example, in 5.8 GHzc50 MHz spectrum available, 5825 to 5875, in 20 MHz channel bandwidth there are 2 non-overlapping channels are available.  5835MHz (5825 to 5845),  5855MHz(5845 to 5865). 3 non-overlapping channels in 2.4GHz(channels 1,6&11) India unlicensed band 2.4 - 2.4835GHz. 5.825-5.875GHz Power: Maximum transmitter output power of 1 Watt ( 4 Watts Effective Radiated Power) (30 dbm) in spread of 10 MHz or higher. 4 Watt peak or 36 dbm EIRP: Equivalent/ Effective isotropic radiated power=36dbm/indoor 16dBm): EIRP=Tx Power(dBm)+Antenna gain (dBi)-cable loss