Implementing Citrix NetScaler 10.5 for App and Desktop Solutions Training

Enterprise QOS Design & Deployment - Good, Bad Or Ugly ? - The Business Side (Case Study)

For last couple of years I have been part of couple of Enterprise Level QOS Deployments. While some of them were tactical and others were completely strategic.

Now QOS is one of those topics in Network Industry which are considered to be highly complex and misunderstood at the same time. The part of the equation is there are lot of moving pieces that must fit together correctly in order to deploy QOS successfully in an Enterprise Environment.

At times I have seen Engineers just copy and paste QOS configurations from some other Enterprise they had access to in past and hoping that would solve the purpose. While in other cases people design QOS policies ensuring top priority for voice and video traffic in an Enterprise Network.

Now many Network Engineers while deploying QOS policies think that they should give highest priority to Voice and Video traffic in their Network. Now one of the common problem here is " Assumptions ".

As a Network Engineer you should always first observe the current state of Network Architecture, Hardware In Use, Documenting List of Critical Business Applications and Understanding their deployment along with Network requirements such as Transport (TCP vs UDP) (One to One Flow, One to Many Flow or Many to Many Flow) (Latency requirements) (Direct vs Redirected Access) (Realtime Vs Interactive) (Transport - LAN vs WAN, Wired vs Wireless) (SP Dependencies, SLA & Service Agreements) (MPLS Layer 2 vs Layer 3 VPNs) etc

The problem usually is that as Network Engineer we always try to understand and solve problems using technologies and tools. Now understanding technology and tools is definitely an important piece here but at the same time you should be able to convert a given business requirement into technical design and solution.

For example most books written around QOS would tell you to mark Voice with Highest Priority like EF and Video probably with AF41. While Voice and Video both are quite sensitive as traffic in a given network but does that also mean those are the most critical ones from Business Standpoint ?. Well if you think carefully that might not be the case in reality. For example an Enterprise client I have been recently working for was into News Paper Business. Now the Editorial Application they use to make news paper had a very tight Latency requirements end to end which was 40msec or less. While If we compare this with voice traffic latency guidelines which is 150msec or less we can certainly find the given requirements are very tight. At the same time this brings an interesting question from design standpoint which is " Shall we still give EF marking to Voice or Shall we use EF marking for Editorial Application ? ". Now if we think from business standpoint or talk to business to figure it out - The answer most likely is going to be that Editorial Application shall be given most priority. Now to make situation a little more complex they had an old Editorial application which was still in use while they were moving to new Editorial Application , so in that sense we now have two Editorial Applications with high latency sensitive requirements :). So we must take of these considerations while designing QOS policy.

Now would QOS policy alone solve the purpose now ?. Well as I mentioned the end to end latency requirements for given Editorial Applications were 40mses or less, which means you need to take a look at WAN Architecture of customer and see how this requirement can be met. Now the company had One Hub Locations in each region of India with approximately 50 remotes sites connecting to each hub site. All Hub locations were connected in partial mesh fashion.

Now the customer WAN comprises 2 MPLS L3 VPN service providers and tons of Point to Point WAN CKTs. Now at high level all looks good. At max we need to ensure that our MPLS VPN service providers are in agreement to accept our QOS markings and give our traffic proper treatment across SP core.

Now the twist here is that while most of remote locations had Cisco ISR G1 or G2 routers, the Core locations were using Cisco Metro Ethernet Switches as MPLS CE device. Now interestingly most Metro Ethernet switches don't support Layer 3 QOS for the purpose of Bandwidth based reservations under LLQ but only L2 QOS and MPLS QOS. So again from the traditional QOS deployment standpoint it could very well be a major pushback.

So as you can see the couple of technical reasons and less understanding or communication with Business makes QOS a complex and misunderstood topic.

The other problem I have seen in field is while Network Engineers try to make policies for things such as Bandwidth reservations under queuing , they don't do traffic pattern analysis properly to figure out correct bandwidth requirements. Ideally you should deploy tools such as NetFlow and let it run for couple of weeks and later analyse it to reach on conclusions for bandwidth usage vs reservation requirements.

So as you can see from this brief post on Non Technical Side of QOS, there are perhaps too many pieces involved to make a QOS deployment successful. While most people say that WAN is having highest potential in terms of SDN use, QOS is probably another key area where SDN and Automation have huge scope IMHO  [ Ever tried to deploy LAN QOS with couple of 6500s, 4500s, 3750, 2950, Nexus in a single setup ? :) ]

HTH...
Deepak Arora
Evil CCIE

Google Gtalk - Finally Dead

Google Talk was one of those applications that I have been using on almost daily basis for years. Although google was keep sending notifications that they gonna stop gtalk for any further use and suggested to use Hang Out application, I think still many people out there were preferring to use old gtalk . But today they seem to kill the application finally

Anyways... Let's see how new Hangout App works. I need to install it's plugin into my chrome browser.

Also expect some interesting Technical posts in march... I know it's been a while.

HTH...
Deepak Arora
Evil CCIE

OSPF Path Selection With Default Information Originate - How You Gonna Fix It ? - Part 2

As OSPF recent design issue discussed here can possibly turn into obnoxious CCIEv5 R&S troubleshooting scenario, I got one email from another friend who also ran into interesting OSPF design issue recently around OSPF default information originate too.

Here is a quick topology of his network design:

At high level the design looks pretty simple. R1 & R2 are peering with WAN cloud using E-BGP. Between R1-R2-R3-R4-R5 we are running OSPF Area 0. To ensure R3-R4-R5 have reachability to external prefixes (Since it's always good to avoid BGP to IGP Redistribution), R1 & R2 are injecting default route into the network using "default-information originate always metric-type 1" option.

Also R1 & R2 are connected to each other over a link running OSPF.

Now let's talk about problem...which is the fun part :)

If R1's WAN connection goes down, R4 can't reach any external prefixes using default route any longer. Whereas at the same time both R3 & R5 don't lose their connectivity to same external prefixes.

Now ideally once R1 find it's WAN interface down, it should get default route from R2 and should be able to route R4's traffic in that direction.

Let me show you same behaviour using CLI :

Before R1's WAN Link goes down

After R1's WAN Link goes down 

No ICMP Packets Received Any Longer on R6

R1 is not installing default route from R2

See if you can figure out " WHY " behind this and offer different ways we can fix this design issue. Feel Free to post you solution, recommendation and findings under comments section. I'll update the post around next weekend with my findings and solutions to the design.

HTH...

Deepak Arora

Evil CCIE



Update

 In SPF Debug

How To Earn 50% Off On JNCIA-JUNOS Exam

While reading about Juniper Certifications on web, today evening I came across interesting URL where they asked to register first and then offered pre-assessment tests. 

As I am currently in middle of my JNCIA-JUNOS prep I thought to take a look on my progress by taking the pre-assessment exam. 

Although I scored far better than I thought to be in pre-assessment exam :) , But since I passed the pre-assessment test, to my surprise they gave me 50% discount voucher for the JNCIA-JUNOS exam.

Here is the URL in case you are interested to earn discount voucher as well :)

https://learningportal.juniper.net/

But in the mean while Jan 2015 First week seems to be good time to go for exam and start the new year with a small bang.

HTH....
Deepak Arora
Evil CCIE