Networking, Python, BigData and Linux

Main areas to Focus for getting NMS/EMS Quality Assurance job in Telecom/Networking field, but not limited to: EMS Vs NMS SNMP V1/V2/V3 or Any other protocols like CORBA,TL1 &CMIP.  Good Understanding on FCAPS. One of the scripting language like Shell Script or TCL or Perl as per ur interest Good Understanding of Operating systems like Windows,Linux & Solaris. Basic Switching & Routing. Mainly STP,DHCP,ARP/RARP,RIP,OSPF & BGP protocols TDM E1/T1 Testing concepts; Feature testing, Regression testing, Sanity tests, performance testing. Also, Testing models like Waterfall model & agile model.       If u want to be in software development in Telecom/Networking field then instead of point 8 above u should be strong in C or C++ or Java. Everything else remains same.

Do you want to crack interview on NMS? Well, you are at right place then J FAQs on NMS (mainly NMS with SNMP):- What is NMS? => It’s a Network Management system which  manages the network nodes like routers, switches, access nodes, servers, hosts and many more. NMS is mainly concerned with how the network nodes are tied up together and hence manage them in terms of networks rather than managing individual nodes. NMS is 3 rd layer in TMN architecture. What are the most common protocols used by NMS to communicate with the nodes? =>SNMP,CORBA,TL1,SSH,Telnet e.tc Which transport layer protocol is used by SNMP? What are the ports used? => SNMP normally uses UDP protocol. NMS uses port 161 to communicate with the agent and listens to port 162 for the traps sent by the agents. How the reliability is achieved in NMS with SNMP? => As UDP is unreliable protocol, there may be chance of traps getting lost. ...

http://www.certificationzone.com/newsletter/SL/IE-RIP-WP1-F03_RLP.html http://searchnetworking.techtarget.com/definition/split-horizon

How Relay Agents Work The following figure shows how Client C on Subnet 2 obtains a DHCP address lease from DHCP Server 1 on Subnet 1. Using a Relay Agent DHCP Client C broadcasts a DHCPDiscover message on Subnet 2 as a UDP datagram over well-known UDP port 67, which is the port reserved and shared for BOOTP and DHCP server communication. The relay agent, in this case a DHCP relay-enabled router, examines the Gateway IP Address field (also known as the giaddr field) in the DHCP message header. If the field has an IP address of 0.0.0.0, the agent fills the Gateway IP Address field with the IP address assigned to the interface on which the DHCPDiscover was received, and forwards the DHCPDiscover message as a unicast message to the DHCP server on Subnet 1. When DHCP Server 1 receives the DHCPDiscover message, it examines the Gateway IP Address field to determine if the packet was relayed. The DHCP server then determines whether it can supply an IP address lease to clients o...

There are basically two ways to assign the IP addresses to any network device. One is Static IP address allocation and the other is dynamic IP address allocation.  Incase of static configuration of IP address we have following disadvantages: There is chance of assigning duplicate IP address to the clients is very high when the network is having so many devices. For every new device that is connected to network, user has to manually assign the IP address. DHCP (dynamic host configuration protocol) is a protocol which is used to assign the IP addresses to clients dynamically. Using DHCP protocol we can overcome the problems faced above due to static IP address assignment. DHCP is a application layer protocol which uses UDP as transport layer. In DHCP configuration, we need to configure one device in a subnet as DHCP server so that all the clients in that subnet receive the IP address from that server dynamically. As DHCP uses broadcast messages (which will be...

Suppose I am a service provider, and providing internet service to a network of 1000 end users. Now, I want to provide another new service lets say IPTV to the users on the same network. How could I do that? Shall I use broadcast so that all the users get IPTV service? How do I provide IPTV service to the only users who are interested for it? Shall I use unicasting to send to the interested receivers?      Well, broadcasting would be a good idea if all the users are interested to use the service and pay for that. What if all the users are not interested and ready to pay for it? Hence I won’t use broadcasting. What about the unicasting? Yes I can provide the IPTV service to interested receivers using unicasting.In this case what I have to do is i  need to send the traffic on one by one basis. If there are 100 users out of 1000 then I have to send a same packet 100 times.oops! Network congestion, bandwidth bottleneck!! So let me not use unicasting for this. What...

Well, MTU(maximum transmission unit) for ethernet is limited to 1500 only.That is because of following main two reasons: 1. When the frame size is too high then chances of signal at physical media being corrupted will be high.And, if there is even a single byte, entire frame needs to be re transmitted which aids overhead significantly.Also, large frame size delays the signal follow. 2. As per the Ethernet frame standard 802.3 there is 2 byte Length field and Ethernet frame standard II there is 2 byte Type field.Based on that numerical 2 byte field Ethernet standard being used will be distinguished.If numerical value is more than 1500 in decimal then it signifies Ethernet standard -II else it signifies  Ethernet standard 802.3. In case the packet size is such that it exceeds the MTU then fragmentation needs to be done. 

Sed, Awk and Find are the excellent unix tools.Following are few problem statements where use of these tools made the work easy.Have a glimpse if these are useful to you as well. Dump only CPU usage and process of the server to a file.       Top –n 1 –d  |  sed ‘1,6d’ |   awk ‘{print  $8 $NF }’ > dump.txt Find a pattern “EMC2” which exists in multiple files under current directory and replace the pattern with “CISCO” in all the files.       Find .  –type f    | xargs sed –i ‘s/EMC2/CISCO/g’       OR find  . –type f   -exec sed –i ‘s/EMC2/CISCO/g’ {} \; Calculate the number of lines between a line containing pattern “XYZ” & a line containing pattern “ABC” in a file. Sed –n ‘/XYZ/,/ABC/p’ | wc –l List the top 3 largest files in a sub-directory.       fi...

STP (Spanning tree protocol) is very simple protocol used in LAN technology to avoid loops in the redundant network. Though it may look very simple, I read many documents to understand how it works and why it is required. However, I hardly could understand it clearly until and unless i worked on it. Yes, we can get many documents/pdfs in the internet but those mayn’t provide you sufficient information to understand it. In this article I am trying to give very clear concept on STP so that one needn’t struggle much to understand it better. Well, before we begun with STP, let me tell you some special characteristics of switches. 1.       Actual Communication at layer-2 happens based on MAC address. 2.       Switches make the forwarding decision based on the destination MAC address. 3.       Switches learn the MAC addresses of devices on their port so that data is properly forwarded to the destination. ...

MPLS(Multiprotocol label switching) is highly emerging network technology which makes use of existing IP technology.MPLS supports traffic engineering which ensures the quality of service and makes best of network bandwidth. MPLS cloud consists of network nodes enabled with MPLS protocols for signalling and data transfer. Label distribution protocol(LDP) & Resource reservation protocol(RSRV) are the major protocols used by most of service providers/vendors.MPLS cloud consists of nodes which are categorized as Provider edge(PE),Customer edge(CE) & Provider(P).Label switched paths(LSP) are maintained between the two PE devices.Switching and forwarding decisions are taken based on the label assigned in the node. Following are the key points which one should know about MPLS: LSPs are maintained between two PEs. LDP protocol is used for normal traffic i.e it doesn't support any protection mechanism. RSVP protocol is used for TE(Traffic engineering) i.e. it sup...

Medical Technology needs to be made strong, its far behind the other areas in technological growth!that may be due to the problem of experimentation :-) We can break many systems before developing any computer software, but we can't break humans :-) I guess this is the good beginning! http://spectrum.ieee.org/nanoclast/semiconductors/nanotechnology/wormlike-nanoparticles-could-be-planted-under-our-skin-for-glucose-monitoring

As we all know that the number of IP devices is increasing exponentially day by day due to continuous enhancement in technologies.Hence today we don't have free IP addresses(IPV4)anymore to be assigned by IANA.Infact we were already having the shortage of IPV4 addresses, but due to the NATing the problem wasn't prominent. However, now the situation is such that NATing can't sustain and adapt the currently demanding technologies further like VOIP, Video Conferencing,IPsec etc. Hence there is a need of IPV6, which overcomes many problems due to IPV4. With the emerge of IPV6, we can have 2^128 addresses which is pretty large number against 2^32 addresses with IPV4.However, there are loads of technological challenges and implementation issues.Hope it will get eased with time.

Suddenly there is a serious accident happened on the way, at the moment your mobile signal strength is below critical label. How does it feel to you? Don't you think this is the worse that can happen? Why people are not able to get their work done in time because of signal problem even though they pay money for that? Sometimes business may be ruined with the millions loss, simply because you are not able to get connected to concerned people in time. And the reason is very simple, our service providers are weak. Why so? They are just overwhelmed by advanced technology, without considering the quality of service? In this article, i am going to mention the two main reasons, and solutions for all the questions rose above. Aspect one:- Today telecom technologies are emerging very fast. Many telecom vendors are developing their own devices with different advanced technology. Hence, people's need won't be fulfilled with the technology built by a single company. As a result of...

Introduction: The BGP flow specification (flowspec) feature allows you to rapidly deploy and propagate filtering and policing functionality among a large number of BGP peer routers to mitigate the effects of a distributed denial-of-service (DDoS) attack over your network. Flowspec model: The BGP Flowspec model comprises of a Client and a Server.The Controller is responsible for sending or injecting the flowspec NRLI entry. The client (acting as a BGP speaker) receives that NRLI and programs the hardware forwarding to act on the instruction from the Controller. In our setup, ExaBGP daemon acts as the flowspec server(Controller) and flowspec supporting cisco IOS-XR  routers act as flowspec clients. GNS topology consisting of IOS-XR routers as provider edge routers is created, and the provider edge routers are connected to the external network so that provider edge routers can talk to ExaBGP node as shown in diagram below. Hence, ExaBGP is respo...

There could be many cases where "error mounting filesystem failed" problem can occur. While starting up ubuntu returned this message with information "please run fcsk manually".After running following command in the debugging terminal solved the problem for me: fsck.ext2 /dev/sda1 (ext2 or sda1 depend upon ubuntu installation on your system). When i looked into the root cause of above error, it was due to improper shutdown.When the battery of the system reach to critically low level(almost 0%), then system goes off.This was the reason shutdown was improper.There could be many solution for this, i have one automated solution for this. In linux, "acpi" command returns the status of battery like % level of battery, charging/discharging etc.Now, we run a script that continuously monitors the status of battery and we can interrupt a graceful shutdown if battery label is below some threshold value and battery is discharging.How to do that?Just copy paste ...

Unix has strong commands/utilities to monitor/debug/control the network.Here are the 5 most useful tools: 1.Tcpdump: Tcpdump, very popular network debugging tool, is used to intercept and display packets transmitted/received on a network.Tcpdump command provide various options like dumping the tcp packets only,udp packets only,packets from a specific ports, dumping traffic of a specific interface(This is very useful when you have multiple interfaces connected to different network) and many more.Some of important examples are: tcpdump -q : It displays the quick output. tcpdump -i eth1: It displays the traffic of eth1 interface. tcpdump udp: It captures the udp traffic tcpdump port : It captures the traffic of a particular port number. tcpdump -w xyz.log: It send the captured packets to a file xyz.log. tcpdump "tcp and !www.xyz.com": It captures the tcp packets except from www.xyz.com 2.nmap: nmap,Network mapper, is a opensource utility for network exploration.nmap dis...

Download your songs from websites with wget and flashgot utilities. Wget is inbuilt utility in Linux and can be used in windows system just downloading wget for windows.use the following link to download the wget for windows: http://www.brothersoft.com/wget-for-windows-download-5755.html In linux, use wget in command line to download single as well as bulk songs.Follow the below example as shown in screenshot for doing the same: Alternatively, download your songs just adding a mozilla firefox addon "flashgot".Here are the steps to download songs using flashgot. (1)Open the url https://addons.mozilla.org/en-US/firefox/addon/220 and click on "Add to Firefox" button. (2)Click on Install now once software installation window pops up. (3) Restart the firefox once installation is successful. (4) Open the website you want to download the songs from and select the song you want to download.example youtube.com (5)Navigate to Tools->Flashgot and click on Flashgot Media...

To implement the integration of virtual network in GNS with the external physical network, I created a virtual topology using Cisco routers as shown in the diagram below: In my experiment above, i've selected 10.10.10.0/24 network and subneted  into small networks each accommodating only two usable IP addresses. The topology shown above is configured and network within the GNS is working fine i.e ping among each node work correctly.        Now, let's jump into the main point of this blog post. Can we connect this virtual network in GNS with the real external network? Can we pass the real traffic from our servers/computers located in different subnet through this GNS topology? The answer is yes, we can. And yes, ideally to the second problem, the computer should have two NIC cards. One is connected to X network & the other is connected to the Y network. Let's say you've a few servers which are located in 192.168.112.0/24 subnet and others are lo...

Recently, I needed to use some advanced features of the Cisco IOS-XR router within the GNS topology. However, GNS doesn't have any ASR 9k series router and also, getting the IOS-XR iso/bin image is very difficult. I decided to use IOS-XRv software to emulate the VM in Oracle virtual box. However, the implementation drove me nuts. It ain't so easy as it looks. Here are the proper steps which ensure IOS-XR router emulation without any issues.   To emulate cisco asr9k router in VirtualBox for GNS, follow these steps: Download  asr9k ova image from the link: https://upload.cisco.com/cgi-bin/swc/fileexg/main.cgi?CONTYPES=Cisco-IOS-XRv.  You need to provide Cisco credentials (or register if not present) Install & configure VirtualBox, follow the link:  http://www.if-not-true-then-false.com/2010/install-virtualbox-with-yum-on-fedora-centos-red-hat-rhel/comment-page-3/ Alternatively, follow these two steps: Download VirtualBox rpm:   wget  http:...