Bufferbloat in switches/bridges

I received the following question today from Ralph Droms.  I include an edited version of my response to Ralph.

On Thu, Jun 20, 2013 at 9:45 AM, Ralph Droms (rdroms) <rdroms@yyy.zzz> wrote:
Someone suggested to me that bufferbloat might even be worse 
in switches/bridges than in routers.  True fact?  If so, can 
you point me at any published supporting data?
Thanks,
Ralph
Ralph,

It is hard to quantify as to whether switches or routers are “worse”, and I’ve never tried, nor seen any published systematic data.  I
Some puzzle pieces of a picture puzzle. wouldn’t believe such data if I saw it, anyway. What matters is whether you have unmanaged buffers before a bottleneck link.

I don’t have first hand information (to just point you at particular product specs; I tend not to try to find out whom is particularly guilty as it can only get me in hot water if I compare particular vendors). I’ve generally dug into the technology to understand how/why buffering is present to understand what I’ve seen.

You can go look at specs of switches yourself and figure out switches have problems from first principles.

Feel free to write a paper!

Here’s what I do know.

Ethernet Switches:

Vendor PSA: Words and Phrases to Avoid in Presentations

Over the years IT professionals have sat through countless presentations, conference calls, and keynotes. We’ve been preached too, explained “the problem”, and forced to bear witness to the the future. During such events all of us have had to step up and explain that we already understand the problem, we know who your company is, and we really just want to know how your product works.

Outside of the normal annoyances, there are several words or phrases that invoke pain and disgust in our hearts, one such phrase came up today. While I won’t mention the source, or berate them anymore than they already have been. I do want to put this list out there for future reference… If I’ve forgotten something that drives you crazy, please, feel free to contact me so I can add it here.

  • Cloud — we’ve jumped the shark with Cloud years ago….
  • Gartner — No one that understands technology cares what Garner says. Period.
  • Magic Quadrant — See above.
  • Single Pane of Glass — An overly obvious marking term.
  • Next Generation — Really? Prove it.
  • Game Changer — See above.
  • Software Defined $something — Just like Cloud, we’ve driven this into the ground
  • And Continue reading

Know Your Competition: Observations From Structure

I spent the day yesterday at GigaOM’s Structure conference in San Francisco trying to see what my colleagues around the technology world are up to these days. If you have haven’t been to Structure, it’s always a good event – well organized, lots of 20-minute discussions and plenty of networking opportunities. There were definitely interesting nuggets shared from a variety of speakers at the show.

For example, I loved it when Ben Haines, formerly of Pabst Brewing, said he worked for “The Department of No.” I’m probably going to “borrow” that because it’s the reason Embrane is trying to help IT, and particularly the networking team. As I wrote in a recent blog post, Don't Hate the Players Hate the Tools, IT and the networking team need to have the tools at their disposal so they have to stop saying no to requests that require immediate action because they can’t react fast enough.

Then there was the CIO from Clorox, Ralph Loura, who said he’s constantly trying to make IT agile. As he said, his goal is to help IT enable business productivity. He gets it! He knows that if he doesn’t, the business units will go off Continue reading

Host Interfaces on UCS FEX 2204 vs FEX 2208

I mentioned in a previous post regarding the connectivity options to each blade if you’re using the appropriate hardware. If you’re using a 2208 FEX, you have 8 upstream ports, each at 10GbE. This means the FEX can support up to 80 Gbps total. You can provide potentially 4:1 oversubscription (math later) to each blade by connecting a 2208 FEX into a blade chassis with blades that can also support 80Gbps each.

Host Interfaces on UCS FEX 2204 vs FEX 2208

I mentioned in a previous post regarding the connectivity options to each blade if you’re using the appropriate hardware. If you’re using a 2208 FEX, you have 8 upstream ports, each at 10GbE. This means the FEX can support up to 80 Gbps total. You can provide potentially 4:1 oversubscription (math later) to each blade by connecting a 2208 FEX into a blade chassis with blades that can also support 80Gbps each.

phpIPAM version 0.8 released

Dear all, I am happy to announce new version of phpipam IP address management – version 0.8. Quite some bugs have been squashed and some new features introduced, like per-group permissions, support for translations, visual subnet displays and other: Permissions

  • New group and permission management;
  • Support for translations;
  • Subnet resizing;
  • Subnet splitting into smaller subnets;
  • Added free space display for nested subnets;
  • Added visual display of subnet usage per IP address;
  • Added truncate network option that deletes all IP addresses in subnet;
  • Added button the updates subnet with RIPE information;

You can demo it here: http://demo.phpipam.net/
You can download it on sourceforge site: phpipam-0.8.

Please note that IE8 is no longer supported!

Special thanks to all the people submitting bug reports, donors, translators and feature testers!

Screenshots:

Screen Shot 2013-06-18 at 10.19.10 PM Screen Shot 2013-06-18 at 10.18.57 PM Screen Shot 2013-06-18 at 10.19.36 PM Screen Shot 2013-06-18 at 10.19.32 PM Screen Shot 2013-06-18 at 10.18.47 PM

Full changelog for this release is:

New features:
----------------------------
+ New group and permission management;
+ Support for translations;
+ Subnet resizing;
+ Subnet splitting into smaller subnets;
+ Added free space display for nested subnets;
+ Added visual display of subnet usage per IP address;
+ Added truncate network option that deletes all IP addresses in subnet;
+ Added button the updates subnet with RIPE information;

Enhancements:
----------------------------
+ Continue reading

On accents, colloquialisms and proprietary extensions

I may not be the most “travelled” person in the world, but over the past couple of years I have managed to find myself in several places across Asia, the Pacific Islands and also the US. One thing has always stood out – Speaking the same language is the hardest part of travelling! Now when I travel to parts of Asia and Im dealing either in hand gestures or with somebody trying their very best speak English (Their English is 1000x better than my Cantonese or my Khmer), and we both make allowances for the difficulty of not speaking the same language.

Sadly, when I travel to the United States and we both attempt to speak “English” nobody can ever seem to understand me. Sometimes its my accent, and other times its the colloquialisms I am using that do not translate effectively, and I am treated by blank stares on the other person trying their hardest not to say “Huh?”.

I’ve learned to deal with this by talking slower and thinking carefully about the words I use to ensure that they dont have some local significance. Anybody who has met me in person knows that I talk loudly, quickly Continue reading

CCIE Lab Exam attempt #2 – How I’m going to study better!

Well it has been just over 7 weeks now since I failed my first attempt at the CCIE Lab Exam in Routing & Switching in Brussels. On the way home on the Eurostar I had vowed to take the weekend off and get straight back on the horse and start labbing again for 4 hours […]

Author information

Roger Perkin

Roger Perkin is the Senior Network Engineer for the European Data Center team for Cobham. Based in Hampshire in the UK, when not designing, building and troubleshooting networks, he can be found studying for his CCIE, kite surfing, cycling and spending time with his family.
You can follow his progress on his CCIE Blog or follow him on Twitter @rogernperkin
or on Google Plus

The post CCIE Lab Exam attempt #2 – How I’m going to study better! appeared first on Packet Pushers Podcast and was written by Roger Perkin.

5 Reasons to Consider Working For a Technology Reseller

For the first several years of my career, I worked for a smaller technology reseller. These types of organizations are often known as value added resellers, or VARs. The role of a VAR is to combine their expertise with some technology they sell in a way that solves the challenges of their customers. The expertise […]

Author information

Paul Stewart

Paul is a Network and Security Engineer, Trainer and Blogger who enjoys understanding how things really work. With nearly 15 years of experience in the technology industry, Paul has helped many organizations build, maintain and secure their networks and systems. Paul also writes technical content at PacketU.

The post 5 Reasons to Consider Working For a Technology Reseller appeared first on Packet Pushers Podcast and was written by Paul Stewart.

NX-OS vPC FEX configuration example


Here's a no frills cheat sheet for a quick vPC and FEX configuration on a pair of Nexus 5000 switches. Refer visio for switch connectivity.



Note, my management network is a /29, just in case you want to configure config-sync between the two NX5K switches. You will need a cfs mcast-address which could be the same as the default gateway used in the management vrf.

On NX5K-1

int mgmt0
 ip add 1.1.1.2/29

vrf context management
 ip route 0.0.0.0/0 1.1.1.1

int eth1/1-2
 desc vPC Peer-Link members
 channel-group 1 mode active

int po1
 desc vPC Peer-Link
 vpc peer-link
 switchport mode trunk
 sw trunk allowed vlan list
 spanning-tree port type network

vpc domain 100
 peer-switch
 role priority 4096
 system priority 4096
 peer-keepalive destination 1.1.1.3 source 1.1.1.2 vrf management

fex 100
 desc "FEX 100"
 pinning max-links 1

fex 101
 desc "FEX 101"
 pinning max-links 1

int eth1/9-10
 channel-group 100

int eth1/11-12
 channel-group 101

int po100
 switchport mode fex-fabric
 fex associate 100
 vpc 100

int po101
 switchport mode fex-fabric
 fex associate 101
 vpc 101

On NX5K-2

int mgmt0
 ip add 1.1.1.3/29

vrf context management
 ip route 0. Continue reading

Powerless Words and Technology

I was introduced by a colleague and mentor a few years ago to the concept of powerless words. Words like “try”, “but”, and “maybe/might”, among others, seem to be our mind’s way of protecting itself against the unknown. After all, we’re only human, right? We can’t control what the world throws at us, right? I encourage you to read the article I linked to as well as this one, which the first article refers to.

Cisco UCS Port-Channeling

Cisco UCS offers a few policies that are applied globally to all equipment in a given UCS domain. These policies are found by selecting the “Equipment” node under the “equipment” tab. (You can also change on an individual chassis basis but the default behavior is for all chassis to inherit this global policy) This is specifically referring to the connectivity between the Fabric Interconnects and the Chassis FEX modules or I/O modules (IOM).

Powerless Words and Technology

I was introduced by a colleague and mentor a few years ago to the concept of powerless words. Words like “try”, “but”, and “maybe/might”, among others, seem to be our mind’s way of protecting itself against the unknown. After all, we’re only human, right? We can’t control what the world throws at us, right? I encourage you to read the article I linked to as well as this one, which the first article refers to.

Cisco UCS Port-Channeling

Cisco UCS offers a few policies that are applied globally to all equipment in a given UCS domain. These policies are found by selecting the “Equipment” node under the “equipment” tab. (You can also change on an individual chassis basis but the default behavior is for all chassis to inherit this global policy) This is specifically referring to the connectivity between the Fabric Interconnects and the Chassis FEX modules or I/O modules (IOM).

RFC 3330 Filtering Using Network Objects

RFC3330 Special-User IPv4 Addresses

Below is a list of special use IPv4 address assigned by IANA and should be blocked inbound on external connections. Most security administrators block RFC1918 but do not realize that RFC3330 includes special use addresses that should not be traversing the internet. RFC3330 includes addresses referenced in multiple RFC's including RFC1918.

   Address Block             Present Use      
   --------------------------------------------------
   0.0.0.0/8            "This" Network              
   10.0.0.0/8           Private-Use Networks                  
   14.0.0.0/8           Public-Data Networks        
   24.0.0.0/8           Cable Television Networks                
   39.0.0.0/8           Reserved but subject to allocation                              
   127.0.0.0/8          Loopback                      
  Continue reading

[Code] UltimateUCSBuild

Name: UltimateUCSBuild.ps1 Author: Matthew Oswalt Created: 6/10/2013 Current Version: v0.2 (ALPHA) Revision Date: 6/18/2013 Description: –THIS SCRIPT IS VERY NEW, EXPECT FREQUENT CHANGES AND IMPROVEMENTS– A script that starts with a completely blank UCS system and configures it to completion. This version of the script is very non-modular and static, but that will change in future versions. My long-term vision for this script is to be simple, yet powerful. I want it to have the ability to provision lots of stuff very quickly, with minimal code changes.

Why We Want to Kill Spanning Tree

To say that Ethernet as a L2 protocol is well-known is an understatement - it’s in every PC network card, and every network closet. Back during the inception of Ethernet, the world needed an open, efficient, standardized method of communicating between nodes on a LAN. Widely regarded as the “mother of the Internet” for many reasons - not the least of which is the invention of the Spanning Tree Protocol - Radia Perlman equated the wide proliferation of Ethernet to the same events that have made English such as popular language on Earth.

[Code] UltimateUCSBuild

Name: UltimateUCSBuild.ps1 Author: Matthew Oswalt Created: 6/10/2013 Current Version: v0.2 (ALPHA) Revision Date: 6/18/2013 Description: –THIS SCRIPT IS VERY NEW, EXPECT FREQUENT CHANGES AND IMPROVEMENTS– A script that starts with a completely blank UCS system and configures it to completion. This version of the script is very non-modular and static, but that will change in future versions. My long-term vision for this script is to be simple, yet powerful. I want it to have the ability to provision lots of stuff very quickly, with minimal code changes.

Why We Want to Kill Spanning Tree

To say that Ethernet as a L2 protocol is well-known is an understatement - it’s in every PC network card, and every network closet. Back during the inception of Ethernet, the world needed an open, efficient, standardized method of communicating between nodes on a LAN. Widely regarded as the “mother of the Internet” for many reasons - not the least of which is the invention of the Spanning Tree Protocol - Radia Perlman equated the wide proliferation of Ethernet to the same events that have made English such as popular language on Earth.
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