Wi-Fi SNR to MCS Data Rate Mapping Reference

I previously posted a picture of an SNR to MCS data rate mapping table that I have compiled based on various sources of credible research. Keith Parsons has kindly put this information into a printable format for reference. You can download them below.

It should be noted that individual devices perform differently. These tables are simply generic estimates that are a good approximation for many Wi-Fi devices. In other words, it's not perfect.

Click to Download Full Version (PDF)

This table maps client SNR values to MCS indexes for the purpose of determining the data rates that clients can achieve based on the signal quality of their connection to the AP.

SNR is also related to RSSI. Two RSSI values are of importance: the Minimum Receiver Sensitivity and the Expected Receiver Sensitivity. The 802.11 minimum receiver sensitivity tables often referenced in research and testing material are the required minimum RSSI values that a radio should be able to decode a given modulation type and encoding rate (MCS index) with a packet error rate (PER) less than 10%. Most 802.11 radios provide better receiver sensitivity than the minimum requirement. Therefore, the "Expected Receiver Sensitivity" reflects the typical receive sensitivity Continue reading

Celebrating CloudFlare’s 4th Birthday

Save the web / CloudFlare

Since CloudFlare launched to the public four years ago today, we've always considered September 27th our birthday. We like to celebrate by doing something nice for our team and also for our customers. Two years ago, for example, we brought a cake into the office and then enabled free IPv6 support for all our customers.

Saturday is our birthday this year, so we decided to celebrate it a few days later when we'd all be back in the office on Monday, September 29th. That actually corresponds to the day we presented at the finals of the TechCrunch Disrupt startup contest where we launched. We ended up coming in second. Mike Arrington, the founder of TechCrunch, said we were basically "muffler repair for the Internet."

Looking back, that's actually not a bad description. At core, CloudFlare's mission is to help build a better Internet by fixing its biggest problems -- its metaphorical rusty mufflers. This year, we thought it would be great to repair a big, ugly muffler that should have been fixed a long time ago.

This Monday, we'll bring a cake into the office. (It'll have to be a lot bigger as our team has grown substantially.) Continue reading

Knowing Your Audience…and Showing It

We all know that you’re supposed to “Know Your Audience.” Doing so improves engagement, and avoids faux pas like “Suggested Tweets.” But recently I realised that this doesn’t have to be subtle. Drop hints early on in your presentation that you’ve taken the time to understand the audience – it can really lift the mood.

Suggested Tweets – Just Say No

Companies that obsess about the wrong kind of metrics think that all they need is to get their message repeated many times. So they give employees & partners a list of “suggested tweets.” These are pre-written Tweets that people can send out from their own Twitter accounts, to “generate buzz.” I have seen many companies do this, and it is overwhelmingly lame. It devalues the message, and devalues those who send out these “suggested tweets.”

In the lead-up to the recent Cisco UCS event, many members of the Cisco Champions program sent out the same set of tweets. When I see the same tweet from several people in my stream, it’s obvious what’s going on. If you’re running a marketing Twitter account, then yeah, I expect marketing messages. But if you’re a real person, and I’ve Continue reading

Classic IOS as a DNS Server

There is an occasional need for a DNS server in the absence of a dedicated host. This may occur in the following situations–

  • Using PAT, Public DNS may return a non-RFC1918 address for internal server
  • Lab/Demo Environment
  • Other Name Resolution challenges in SOHO, SMB or Branch Office

When these corner-case challenges present, an IOS router may be beneficial by providing basic DNS functions. Assuming the router already has Internet connectivity, the configuration is straightforward–

//enable the dns server functionality
IOS-DNS(config)#ip dns server 

//if public requests should be resolved, configure one or more name
//servers as resolvers and confirm domain-lookups are enabled
IOS-DNS(config)#ip name-server 8.8.8.8 8.8.4.4
IOS-DNS(config)#ip domain-lookup

At this point the router should perform DNS resolution by relaying requests to the public name servers in the configuration. Hosts could use any IP address on the device in their DNS configuration. ACLs should be used to block DNS requests to interfaces that aren’t servicing clients.

To create DNS records for local resolution, the ip host command can be used.

IOS-DNS(config)#ip host ?
  WORD  Name of host
  view  Specify view
  vrf   Specify VRF

IOS-DNS(config)#ip host www.example.com ?
     Default telnet port number
  A.B.C.D     Host IP address
  additional  Append addresses
  mx          Configure a  Continue reading

Do shellshock scans violate CFAA?

In order to measure the danger of the bash shellshock vulnerability, I scanned the Internet for it. Many are debating whether this violates the CFAA, the anti-hacking law.

The answer is that everything technically violates that law. The CFAA is vaguely written allowing discriminatory prosecution by the powerful, such as when AT&T prosecuted 'weev' for downloading iPad account information that they had made public on their website. Such laws need to be challenged, but sadly, those doing the challenging tend to be the evil sort, like child molesters, terrorists, and Internet trolls like weev. A better way to challenge the law is with a more sympathetic character. Being a good guy defending websites still doesn't justify unauthorized access (if indeed it's unauthorized), but it'll give credence to the argument that the law is unconstitutionally vague because I'm obviously not trying to "get away with something".


Law is like code. The code says (paraphrased):
intentionally accesses the computer without authorization thereby obtaining information
There are two vague items here, "intentionally" and "authorization". (The "access" and "information" are also vague, but we'll leave that for later).


The problem with the law is that it was written in the 1980s before the web Continue reading

Change HTTP reply content with AppShape++

Lab goal

When a clients asks for beta/a2.html, return "Hello" instead.

Use VIP 10.136.85.14

Setup


The loadbalancer is Radware's Alteon VA version 29.5.1.0

The initial Alteon VA configuration can be found here.

Notice the group and hosts are preconfigured:

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/c/slb/real 1
        ena
        ipver v4
        rip 10.136.85.1
/c/slb/real 2
        ena
        ipver v4
        rip 10.136.85.2
/c/slb/real 3
        ena
        ipver v4
        rip 10.136.85.3
/c/slb/group 10
        ipver v4
        add 1
        add 2
        add 3

Alteon configuration

First, lets configure the VIP/virt.

Remember routing! The returning traffic needs to go through the Alteon, otherwise TCP will break. So we also need to configure Proxy IP/SNAT so return traffic will go through the Alteon.


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 /c/slb/virt 85_14
        ena
        vip 10.136.85.14
 /c/slb/virt 85_14/service 80 http
        group 10
 /c/slb/virt 85_14/service 80 http/pip
        mode address
        addr v4 10.136.85.200

Next we need to write the Appshape++ script:

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Plexxi Pulse—Preparing for Big Data

Plexxi Pulse—Preparing for Big Data

As enterprises launch Big Data platforms, it is necessary to tailor network infrastructure to support increased activity. Big Data networks must be constructed to handle distributed resources that are simultaneously working on a single task—a functionality that can be taxing on existing infrastructure. Our own Mike Bushong contributed an article to TechRadar Pro this week on this very subject where he outlines the necessary steps to prepare networks for Big Data deployments. He also identifies how software-defined networking can be used as a tool to alleviate bandwidth issues and support application requirements when scaling for Big Data. It’s definitely worth a read before you head out for the weekend.

In this week’s PlexxiTube of the week, Dan Backman explains how Plexxi’s Big Data fabric mitigates incast problems.

Check out what we’ve been up to on social media this September. Enjoy!

The post Plexxi Pulse—Preparing for Big Data appeared first on Plexxi.

Safe from Shellshock: How to protect your home computer from the Bash shell bug

On the surface, the critical “Shellshock” bug revealed this week sounds devastating. By exploiting a bug in the Bash shell command line tool found in Unix-based systems, attackers can run code on your system—essentially giving them access to your system. Bad guys are already developing exploits that use Shellshock to crack your passwords and install DDoS bots on computers. And since Bash shell is borderline ubiquitous, a vast swath of devices are vulnerable to Shellshock: Macs, Linux systems, routers, web servers, “Internet of Things” gizmos, you name it.To read this article in full or to leave a comment, please click here

IPv6 in my streaming media? More likely than you think!

Not that I go out of my way to endorse one project/product over another, there is one that I have recently fallen in love with for streaming my media. Especially when it can use IPv6! So I needed a cross-platform solution for my streaming media needs. I was originally using XBMC, but only had it tied into the TV. I use several other computers and devices, in other locations outside of the house. So I read up on Plex. Got it installed with little to no effort, and could readily access my content where ever I was. I even tested this on my last trip to London, UK and was able to get a decent 1.2mbit/s stream from my house. Only issue was that it wasn’t using IPv6 in the app or accessing via plex.tv (server on that site only comes up with an IPv4 address).

So poking around I discovered 2 things: 1) I could access the Plex server directly at the IP/hostname of the server, and 2) there was a checkbox to enable IPv6!!

plex-ipv6

Simply browse to your Plex server, click on the settings icon (screwdriver + wrench), select Server, click on Networking and then “Show Continue reading

Many eyes theory conclusively disproven

Just because a bug was found in open-source does not disprove the "many eyes" theory. Instead, it's bugs being found now that should've been found sometime in the last 25 years.

Many eyes are obviously looking at bash now, and they are finding fairly obvious problems. It's obvious that the parsing code in bash is deeply flawed, though any particular bug isn't so obvious. If many eyes had been looking at bash over the past 25 years, these bugs would've been found a long time ago.

Thus, we know that "many eyes" haven't been looking at bash.

The theory is the claim promoted by open-source advocates that "many eyes makes bugs shallow", the theory that open-source will have fewer bugs (and fewer security problems) since anyone can look at the code.

What we've seen is that, in fact, very few people ever read code, even when it's open-source. The average programmers writes 10x more code than they read. The only people where that equation is reversed are professional code auditors -- and they are hired primarily to audit closed-source code. Companies like Microsoft pay programmers to review code because reviewing code is not otherwise something programmers like to do.

From Continue reading

MidoNet for the Overlay, Cumulus Linux for the Underlay. Like Coffee and Cream.

VTEP is not the only way MidoNet customers can use a switch that runs Cumulus Linux as the underlay (physical network) for the virtual, overlay networks.

We’ve announced our partnership to work with Cumulus Networks earlier in 2014 to use Cumulus Linux as a Layer-2 VxLAN Gateway to bridge VLANs in the virtual network world to the VLANs in the physical world.

We’ve shipped that code as part of MidoNet version 1.6.

We now want to talk about how VTEP is not the only way MidoNet customers can use a switch that runs Cumulus Linux as the underlay (physical network) for the virtual, overlay networks.    Just don’t think of running a set of gateway switches as the only way to benefit from these devices, we see many opportunities and benefits.

Here are some examples why it makes sense :

Automation

Remember that Cumulus Linux IS Linux. It’s not a switch OS that just happens to be based on Linux.  It offers cloud automation capabilities that is so crucial to customers who are adopting to move towards building a Cloud. If you listen to Customers, Systems like Chef and Puppet are widely used in the deployment of systems like OpenStack, Continue reading

FCC advised on Remediation of Server-based DDoS Attacks

Yesterday, the Communications Security, Reliability and Interoperability Council (CSRIC), a federal advisory committee to the Federal Communications Commission (FCC), submitted its final report on Remediation of Server-based DDoS Attacks.

The CSRIC’s Working Group 5 was tasked with developing recommendations for communications providers to enable them to mitigate the impact of high volume DDoS attacks launched from large data center and hosting environments.

The final report includes a comprehensive look at the DDoS threat landscape, covering everything from the massive size of today’s attacks, to the potential for collateral damage. The report describes how DDoS attacks are becoming increasingly complex, how they are being used as a diversion “to distract security resources while other attacks are being attempted, e.g., fraudulent transactions.” The report also discusses how botnet architectures are becoming more sophisticated and difficult to trace.

Given this complex and challenging threat landscape, we were grateful for the opportunity to contribute. The CSRIC has adapted Arbor Networks best practices for DDoS incident response as the Six Phases for DDoS Attack Preparation & Response.

Web_SixPhases_Final

Roland Dobbins, senior analyst with Arbor’s Security Engineering & Response Team (ASERT), served as the Internet sub-group chairman of CSRIC IV WG5 – Server-Based Continue reading

PQ Show 33 – Intel Rack Scale Architecture – Real or Impractical ?

At the IDF 2014 conference, Intel made a big song and dance about their Rack Scale Architecture which removes the need for “top of rack” networking and changes the nature of servers in a big way. My initial impression is that this has limited application in the enterprise or cloud providers but might be useful […]

Author information

Greg Ferro

Greg Ferro is a Network Engineer/Architect, mostly focussed on Data Centre, Security Infrastructure, and recently Virtualization. He has over 20 years in IT, in wide range of employers working as a freelance consultant including Finance, Service Providers and Online Companies. He is CCIE#6920 and has a few ideas about the world, but not enough to really count.

He is a host on the Packet Pushers Podcast, blogger at EtherealMind.com and on Twitter @etherealmind and Google Plus.

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The post PQ Show 33 – Intel Rack Scale Architecture – Real or Impractical ? appeared first on Packet Pushers Podcast and was written by Greg Ferro.

Three Big SDN Questions for Your SDN Development Plan

SDN is happening. What questions should you be asking about your own development plan to learn SDN skills?

I’ve been thinking about this question in preparation for an upcoming Interop Debate on October 1st, where we’ll be discussing the options to pursue traditional certifications versus learning about SDN. Today’s post begins a series of posts related to topics surrounding that debate. To begin, we’ll look at three big-picture questions you should ask when you get serious about studying about SDN.

Overview

How much of your skill set happened to you, rather than being something you planned? How much of your learning relates to surviving today’s job tasks, versus learning for the future?

Let’s face it, many days, we do the job in front of us, with little time to devote to learning something unrelated. However, that’s a fundamental question for any IT knowledge-based worker. Do you have a development plan? Do you spend time working that plan? And now with SDN happening… how should you revise that plan in light of SDN? In the time you can devote this week/month/year, what should you be learning about SDN?

Some people will wait to learn SDN when the next project Continue reading

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