The To DS and From DS Fields

Currently I’m studying for the Certified Wireless Analysis Professional (CWAP) exam and I’m rereading the study guide and I found the chapters that examined the different fields and elements present in the MAC header most interesting. I had a rough idea, but during my studies learned a great deal more about the unique fields and elements dedicated to wireless that keep the network functioning and help packets get delivered. Two fields of particular interest are the To Distribution System (To DS) and From Distribution System (From DS) and how these fields determine if the frame is leaving or entering the wireless environment.

Distribution System

Just a quick definition of the distribution system and basically the DS is the infrastructure that connects multiple access points together to form an Extended Service Set (ESS). The DS is typically an 802.3 Ethernet wired network, but it doesn’t have to be, and the DS can even be a wireless back haul.

MAC Header & Frame Control Field

Lets now look at the MAC header which can contain four address fields. The number of address fields is a major difference between Ethernet frames, which only use two address fields, and wireless frames that could Continue reading

Role inversion

At the OpenStack summit in Atlanta this week there was a very interesting phenomenon. Vendors that have been traditionally positioned in the I.T space seemed to be directing their energy around OpenStack on the carrier / telecom space; while vendors traditionally in this space where doing the best they could to get beyond it and into non-traditional I.T deployments.

As an example, canonical’s booth was primary advertising their “Carrier Class OpenStack” and RedHat seemed very interested in NFV; with several senior developers organizing a cross project NFV subteam to focus on how OpenStack can be a better fit for carrier data-centers.

The traditional telecom vendors on the other hand seemed to be rather less sanguine on the NFV market. At least when it comes to the timelines required to get to production deployments: 2018 seems to be a reasonable target.

I don’t currently have access to market research data; but i would be very curious to take a look at it and how it is being interpreted. Either the I.T. vendors are over-investing or the traditionally Service Provider focused vendors are under-investing in this space. Cisco, for instance, which is typically quite business savvy is nowhere to Continue reading

OpenContrail at the summit

There was a lot happening at the OpenStack summit in Atlanta this week. I got the opportunity to meet several of the most active OpenContrail developers; and envangilize the project with several people that are looking for an OpenStack networking solution that meets their needs.

The buzz on Neutron can be sumarized by: the default implementation of neutron doesn’t work. Many users find that running neutron service rack with l3-agent and dhcp agent isn’t working out for them: the neutron router is a choke point for traffic; there is no resiliency and some of the services (e.g. DHCP) are prone to melt down. This seemed to be the rought consensus of those who i spoke with (admitedly a rather un-scientific sample).

It is easy to explain the advantages of the OpenContrail implementation in this context. By implementing a fully distributed router implementation as well as distributing the DHCP, metadata proxy and floatingip functionality, OpenContrail solves most of the current pain points of Neutron.

On the other side, some of the users I spoke to where often concerned with the relativly small size of the community. Hopefully this weeks annoucement of the OpenContrail Advisory Board will help aliviate this concern. Continue reading

Cisco Live US 2014 is upon us!

  Just wanted to put out a quick post and wish all the attendees, exhibitors, and staff safe travels! I know we all have a busy and exciting week ahead of us!  Make sure you stop by the Social Media lounge and say hello and meet some new friends. The social media lounge is in Moscone […]

My pinboard bookmarks for 17 May 2014

Things of note that were discovered on the web this week.

CriticMarkup

Can't do editing in Markdown eh? Obviously you haven't seen CriticMarkup. Looks very cool indeed!

markdown

java - Excluding tests from being run in IntellIJ - Stack Overflow

This is how to exclude integration tests being run in IntelliJ I've been using this for unit testing the OpenDaylight OVSDB library with the regex ^(?!(^.*(IT).*?$)).*$ and it works well!

intellij, java, testing, junit

Maven Troubleshooting FAQs

A presentation with troubleshooting Maven issues which is a necessary skill if you plan to do any development in Java.

java, maven

Elephant Detection in the vSwitch With Performance Handling in the Underlay

As we’ve discussed previously, the vSwitch is a great position to detect elephant, or heavy-hitter flows because it has proximity to the guest OS and can use that position to gather additional context. This context may include the TSO send buffer, or even the guest TCP send buffer. Once an elephant is detected, it can be signaled to the underlay using standard interfaces such as DSCP. The following slide deck provides and overview of a working version of this, showing how such a setup can be used to both dynamically detect elephants and isolate mice from queuing delays they cause. We’ll write about this in more detail in a later post, but for now check out the slides (and in particular the graphs showing the latency of mice with and without detection and handling).


Lying Headline From Business Insider: Cisco Is Going To Crush VMware

Received an email about this article Chambers: Cisco Is Going To Crush VMware – Business Insider. The title  strongly suggests that John Chambers said “Cisco is going to crush VMware” but it’s a lie. The closest that the article content gets is: A cheerful John Chambers told Wall Street analysts on Wednesday that his plan to crush […]

The post Lying Headline From Business Insider: Cisco Is Going To Crush VMware appeared first on EtherealMind.

Could Cisco ACI Kill APM?

APM TargetNote – This is ALL 100% speculation on my part. I may be WAY off base with what you are about to read, and if you know something I don’t, feel free to correct me in the comments below.

I attended the Cisco Live Local Edition event here in Nashville,TN last month. It was an all day event that gave a variety of presentations in different focus areas. While I spent the bulk of my time in the routing/switching/wireless/security presentations, I made a point to sit in on one in the data center track. It was entitled Data Center Fabric Futures. This session spent a lot of time talking about Cisco’s Application Centric Infrastructure(ACI) technology, so I was curious to learn a bit more about it since the company I work for sells a fair amount of Cisco Nexus switching.

If you want a little more information about Cisco’s ACI technology, here’s some really good writing on that subject:

Insieme and Cisco ACI [Part 1] – by Matt Oswalt

Insieme and Cisco ACI [Part 2] – by Matt Oswalt

Cisco’s ACI (Insieme) Launch – by John Herbert

While the presentation was moving along, one particular aspect of ACI caught my Continue reading

Pseudowire FAT Interoperability

I usually don’t think much about Pseudowires Sub-TLV until I encountered two IOS-XR boxes that didn’t use the same value and didn’t forward any packets. There is a special corner case of pseudowires using Flow Labels Transport (FAT) that can cause unexpected behavior and if you don’t watch out you might drop traffic. In this post I’ll go over the details of using FAT with different IOS-XR versions and what can go wrong.

Flow Aware Transport  pseudowire (RFC6391) is a type of L2VPN that operates over MPLS. The main benefit of it is that it implements a mechanism which allows you to load-balance one pseudowire over multiple equal cost paths (i.e. ECMP). ECMP of a pseudowire becomes an advantage when transporting large amount of traffic such as 10Gbps or more. FAT is a special interface sub-TLV that’s negotiated between two PE.

The problem relates to Flow Aware Transport (FAT) pseudowires where one side terminating router operates the IOS-XR version 4.3.2 and the other any version up to 4.3.1. The symptom is lack to forwarding of tunneled packets. Both sides show PW as up and operational but no traffic is being forwarded over it. Continue reading

The SDN Ecosystem

As a follow on to my blog about building a business case for an SDN deployment, there are now dozens of companies offering SDN-related products – so many that you might find it difficult to separate the hype from the meat. Let’s look at some categories of SDN products and how each of them fits into an overall SDN solution.

The key components of an SDN solution are ASICs, switches, a controller, and the applications or services that run over the network.

ASICs

ASICs have a long history in networking by driving scale and performance. In a clock cycle, very complex tasks can be accomplished. Without the ASIC, the central CPU would be overwhelmed performing those same tasks (remember those so called “one arm routers”). The need for ASICs created a new set of suppliers such as Broadcom, Marvell and Mellanox, and most recently Intel through its acquisition of Fulcrum. We can expect more and more specialization in ASICs as the industry pivots on the SDN theme. Over the last decade, the merchant silicon vendors have diversified and specialized products for vertical markets. For example, an ASIC optimized for the data center might have VxLAN support, while another tuned Continue reading

IPv6 at Home – Prefix Delegation

As many of you may know, I used to move packets around for a living.  I’m not doing that any more, but I’m still administering my own little home network and keeping my hand in.  After my old consumer-grade ADSL modem packed it in, I decided that I’d like to do something a bit more […]

Author information

Matthew Mengel

Matthew was a Senior Network Engineer for a regional educational institution in Australia for over 15 years, working with Cisco equipment across many different product areas. However, in April 2011 he resigned, took seven months of long service leave to de-stress and re-boot before becoming a network engineer for a medium sized non-profit organisation. At the end of 2013, he left full-time networking behind after winning a scholarship to study for a PhD in astrophysics. He is on twitter infrequently as @mengelm.

The post IPv6 at Home – Prefix Delegation appeared first on Packet Pushers Podcast and was written by Matthew Mengel.

Response: Math and Monitoring

Monitorama has posted the videos from their conference PDX 2014 and I’ve been watching them during concentration breaks. Most of them are very good story telling from real practitioners who have real world experiences. I wanted to call out just two that impressed me deeply. Noah Kantrowitz’s session from Monitorama PDX 2014 talks about using […]

The post Response: Math and Monitoring appeared first on EtherealMind.

Cisco Live – The Minimalist Packing List

Cisco Live 2014 is right around the corner! It’s almost time to start packing. The other day, Keith Miller (@packetologist), a first-time Cisco Live attendee, asked me on Twitter:

I have a bit of a reputation among some of my consulting clients as being ready for just about anything. Normally, that means my laptop bag weighs about 50 lbs. But for Cisco Live, I choose to travel light. I’ve seen people in the airport on the way to, and from, the event with a LOT of stuff. Sure, some folks are presenters or carrying company stuff but for the rest, you probably just have too much stuff.

Why choose to travel as light as possible? Here are just a few reasons:

  1. Airline bag check fees
  2. Airlines are great at losing/abusing your stuff once its out of your hands
  3. Due to #1, everyone is always fighting for room in the overhead bins and you end up checking your “carry on” anyway
  4. If you land early, you have to check your 3 tons of bags, or else Continue reading

Load balancing large flows on multi-path networks

Figure 1: Active control of large flows in a multi-path topology
Figure 1 shows initial results from the Mininet integrated hybrid OpenFlow testbed demonstrating that active steering of large flows using a performance aware SDN controller significantly improves network throughput of multi-path network topologies.
Figure 2: Two path topology
The graph in Figure 1 summarizes results from topologies with 2, 3 and 4 equal cost paths. For example, the Mininet topology in Figure 2 has two equal cost paths of 10Mbit/s (shown in blue and red). The iperf traffic generator was used to create a continuous stream of 20 second flows from h1 to h3 and from h2 to h4. If traffic were perfectly balanced, each flow would achieve 10Mbit/s throughput. However, Figure 1 shows that the throughput obtained using hash based ECMP load balancing is approximately 6.8Mbit/s. Interestingly, the average link throughput decreases as additional paths are added, dropping to approximately 6.2Mbit/s with four equal cost paths (see the blue bars in Figure 1).

To ensure that packets in a flow arrive in order at their destination, switch s3 computes a hash function over selected fields in the packets (e.g. source and destination IP addresses Continue reading

Integrating Route Explorer with the OpenDaylight Controller for SDN Provisioning

Integrating Route Explorer with the OpenDaylight Controller for SDN Provisioning

by Steve Harriman, VP of Marketing - May 13, 2014

Despite the hype surrounding SDN, no one can afford to leap frog to the new technology. They must have a strategy to integrate the new with the old to reap the biggest benefits. Packet Design has taken its first step in helping customers do so. We’ve integrated Route Explorer with the OpenDaylight controller to automate SDN provisioning of RSVP-TE tunnels. For network engineers, this means eliminating the manual process of creating tunnels. They can simply plan it in Route Explorer and have the OpenDaylight controller automatically provision it. Some of our early adopter customers – especially service providers – are very happy about this. 

OpenDaylight only supports TE tunnels today, but our integration is an example of how we can support SDN in hybrid environments. Our analytics technology is unique because it allows us to build SDN conforming applications in the presence of non-conforming applications. You don’t have to do a forklift hardware upgrade in the network or build a brand new network architecture where the controller provisions everything. We are able to demonstrate provisioning of RSVP-TE tunnels in hybrid environments Continue reading

Routing-Bits SP Update

    The next installment of the SP handbook is now available. It includes two new chapters and an extra appendix. Please check your email for instructions. Contact me if your email address has changed.Filed under: CCIE SP
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