October 02, 2005

NSSA (ABR+ASBR)

Sometime you face to a router in OSPF which is an ASBR NSSA and it's an ABR as well so in this situation you've two external LSAs on that router, one is LSA type 7 which is advertised to NSSA area and other is LSA type 5 which is advertised to other not stub area.
now in some case you don't need to advertise LSA 7 in NSSA area and you need the router acts as ABR router for NSSA area so to prevent advertising LSA 7 to NSSA area at Cisco routers you can use the following command under ospf process :
area area_id nssa no-redistribution
nssa-ospf.gif
at the above scenario you can see a router which is an ASBR NSSA router and an ABR router so to prevent IGRP advertisements (external routes) to NSSA area you should do by the below commands :
router ospf 100
area 1 nssa no-redistribution

Posted by Mehrdad at 10:20 AM

July 18, 2005

Active directory demotion

A trick when you're going to uninstall active directory on win2000 and the demotion failed! through dcpromot or dcpromot /forceremove commands
At regedt32 modify the following key from lanmanNT to serverNT :
HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\control\ProductOptions\ProductType
when you done it, restart your server then delete NTDS directory after that you should change server from member domain to member of workgroup.
after this alteration you must restart server , now your active directory is demoted and you can install a fresh DC or forget it ;-)

Posted by Mehrdad at 01:10 PM | Comments (0)

April 19, 2005

Robot, QRIO

qrio_01.jpg

What's Robot? in fact we don't have a specific definition for robot but we can define robot with some specification.usually it's a mechanical machine but these days we can see some software robots so it can be non mechanical, it's reprogrammable and it can intelligence. for instance in industry it move material,part,tools through variable programmed.
Have you ever thought about future and robots? in fact how they would can change our social life in future? how can AI (Artificial Intelligence) help them for thinking like human?
I would like to see those days when we live with intelligence robots.
As you know Sony is a big company and they work on a wonderful project that named QRIO (quest and curious).Sony's goal is personal entertainment so they produced QRIO , it embodies advance technologies in motion control, communication , artificial intelligence.
Major technology includes stable dynamic walking, dancing and running, full arm movement allowing throwing a ball, voice/face recognition, stereoscopic vision, obstacle avoidance, visual mapping, wireless network and ....
you can find more information about QRIO at sony web site http://www.sony.net/SonyInfo/QRIO/

Posted by Mehrdad at 12:02 PM

April 04, 2005

NAT Traversal

natt.jpg
Probably you heard IPSEC ESP doesn't work through PAT connection because when the PAT wants to modify ESP layer 4 header it faces to problem. why? because it's encrypted and PAT can't change source port. don't worry the RFC 3948 written by four major companies (F-Secure Corporation, Microsoft, Cisco and Nortel) at jan.2005, can help us but what's your VPN vendor? because all vendor haven't implemented yet.
How does it work?
In fact this protocol defines methods for encapsulate and decapsulate ESP packet inside the UDP for traversing through network address translators.

nattp.jpg

It's so good for any network which are using PAT and they want to have IPSEC ESP from any hosts of its network.really this protocol help to limitation IP V4 (special thanks to the IETF (Internet Engineering Task Force) for fix this problem in working ESP through PAT)

See detail of this protocol from the following URL :
UDP Encapsulation of IPsec ESP Packets RFC
http://www.faqs.org/rfcs/rfc3948.html

Posted by Mehrdad at 05:39 PM

March 29, 2005

QoS , P2P and NBAR

Data classification is one of more important things in QoS but how we can classified data flow through cisco devices (with proper IOS)?and in this days what's important to prioritize?
Data classification depends on each network data flow, for example when you're using voice,video,citrix application and so on , you should plan a strategy for your classification data.

Generally data network is classified to following :
- Voice
- Mission critical (application like citrix)
- Transactional (E-commerce)
- Best-effort (web,email and ...)
- Less-Than-Best-effort (P2P)
*Note : Cisco recommend that your classification doesn't exceeded from 4 or 5 categorize.

These days Peer 2 Peer file sharing applications are a issue for any network which is connected to internet, because it has many data traffic for instance video,mp3 and other larg files so it cause bad situation when the newtrok has congestion.what do you think when you haven't QoS and all of data flow has same priority? yes ofcourse your voice and other low latency data are experienced loss data.
Cisco content networking architecture help you to classified data in later 4-7, it called Network Based Application Recognition (NBAR) so it can regognition some P2P application like Kazza however it depends on PDLM (packet description language module) which is loaded in your cisco device.
You should download the latest PDLM from Cisco web site to up to date application signatures.

In another aspects NBAR can recognize the HTTP GET packets contain the URL through hostname, mime type as well as it has protocol discovery analyzes application traffic pattern in real time and discovery which traffic is running on the network.it uses SNMP to provide that information.

Regarding to this article see the following commands :
ip nbar pdlm pdlm-file
class-map [match-all | match-any] class-name
policy-map policy-name
class class-name
service-policy output
service-policy input
match protocol protocol-name (like kazza)
match protocol fasttrack file-transfer "regular-expression"
ip nbar protocol-discovery
snmp-sever enable traps cndp

Posted by Mehrdad at 08:48 PM

March 19, 2005

Artificial Intelligence

ai.jpg

In the early 1950s Herbert Simon, Allen Newell and Cliff Shaw conducted experiments in writing programs to imitate human thought processes. The experiments resulted in a program called Logic Theorist, which consisted of rules of already proved axioms. When a new logical expression was given to it, it would search through all possible operations to discover a proof of the new expression, using heuristics.
This was a major step in the development of AI. The Logic Theorist was capable of quickly solving thirty-eight out of fifty-two problems with proofs that Whitehead and Russel had devised. At the same time, Shanon came out with a paper on the possibility of computers playing chess. Though the works of Simon et al and Shanon demonstrated the concept of intelligent computer programs, the year 1956 is considered to be the start of the topic Artificial Intelligence. This is because the first AI conference, organised by John McCarthy, Marvin Minsky, Nathaniel Rochester and Claude Shanon at Dartmouth College in New Hampshire, was in 1956. This conference was the first organised effort in the field of machine intelligence. It was at that conference that John McCarthy, the developer of LISP programming language, proposed the term Artificial Intelligence. The Dartmouth conference paved the way for examining the use of computers to process symbols, the need for new languages and the role of computers for theorem proving instead of focusing on hardware that simulated intelligence.

Continue reading "Artificial Intelligence"

Posted by Mehrdad at 03:25 PM

 


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