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ASK THE EXPERT - WIRELESS 11.N

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Dec 14th, 2009

Welcome to the Cisco Networking Professionals Ask the Expert conversation. This is an opportunity to learn more about wireless 11.n with Cisco experts Jeevan Patil. Jeevan has been with Cisco for the past 10 years. For the first 5 years he was a software engineer working on security, network management and wireless. In the past 5 years Jeevan has been the Product Manager on various initiatives such as Client hardware, CCX, standalone(Autonomous) software, WLSE hardware and software, Access Points 521 series, 1250, 802.11n etc. Currently Jeevan is focused on 802.11n standards and Access Points.

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bapatsubodh Mon, 12/14/2009 - 10:51

Hi,

1. For 802.11n which Cisco AP currently support  this standard.  Is it possible  to upgrade the existing Cisco AP to support the 802.11n ? ( 1250 Series )

2. It can deliver upto 600 mbps how many maximum number of users can be connected till the device becomes saturated?

3.Does cisco has compatible PCI or laptop cards to be installed on desktop or notebooks to take maximum possible advantage of high speed?

Thanks

Subodh Bapat

jepatil Wed, 12/16/2009 - 10:42

Hi Subodh,

Firstly thank you for giving me an opportunity to respond to these questions about 11n. Please see inline -

1. For 802.11n which Cisco AP currently support  this standard.  Is it possible  to upgrade the existing Cisco AP to support the 802.11n ? ( 1250 Series )

Jeevan > Cisco AP 1140, AP 1250 and the ISR 860, 880 and 890 support 802.11n.

The 802.11n standard was ratified in September 2009 and did not require any mandatory new hardware or software changes to products that were draft 2.0 802.11n compliant. Therefore if you have purchased any of those products from Cisco you are already 11n compliant. We would recommend upgrading to the latest software release simply from the perspective of having the most stable code and having maximum functionality.

2. It can deliver upto 600 mbps how many maximum number of users can be connected till the device becomes saturated?

Jeevan > One radio with two spatial streams delivers a maximum of 300 Mbps and thus a dual-radio AP would deliver upto 600Mbps. However as you know typical traffic considerations as observed even with ethernet switching show oversubscriptions. Cisco's recommendations about number of clients per AP continue to be the same with 11n as that with a/g .. namely 15 clients per radio or about 30 clients per AP.

3.Does cisco has compatible PCI or laptop cards to be installed on desktop or notebooks to take maximum possible advantage of high speed?

Jeevan > Cisco does not offer any PCI or laptop cards with 802.11n technology. However we strongly recommend you to take a look at the two most important metrics - CCX compatibility and WFA certification which are available through leading partners such as Intel. This would ensure enterprise-grade performance

Thanks

stephenshaw Mon, 12/14/2009 - 13:09

Hi,

we are just starting to roll out the 1252 WAPs; some will be standalone, others will use WLCs. My question is related to the 802.11n standard and how the actual wireless signalling can do full duplex? Or is this something that Cisco plan on a little bit down the road?

Thanks,

Steve

jepatil Wed, 12/16/2009 - 15:19

Hi Steve,


No. The 802.11 standard specifies a Carrier Sense Multiple Access/Collision Avoidance (CSMA/CA) transmit-recieve environment. Therefore, all 802.11 are half-duplex/simplex in nature. This was the case in a/b/g and the same holds true for 11n.

Regards,

Jeevan

Leo Laohoo Thu, 12/17/2009 - 13:43

All 802.11 a/b/g/n are half duplex standard, period.  If a competing manufacturer (particularly the sales/pre-sales team) tells you otherwise, I'd recommend you ask for a demonstration.

chaijoo_lau Mon, 12/14/2009 - 22:18

What happen to customer that own 1250 Series and/or 1140 Series Lightweight Access

Point with 4400 Series Wireless LAN Controller? Does their Wireless LAN compliant with the final 802.1n standard?

jepatil Wed, 12/16/2009 - 14:44

The ratification of the 11n standard in Sep 2009 added no mandatory requirements in addition to those defined in draft 2.0

Thus customers that already own the AP1250 and 1140 are fully covered and do not need to update any software. Although recommendation is to migrate to the latest software releases to get the fullest and most stable functionality.

jmprats Tue, 12/15/2009 - 00:03

Hi,

1. If you only have 802.11g clients, do you have more capacity for them if you use a 802.11n AP or you only can use this capacity with 802.11n clients? I mean can you connect more 802.11g clients in a 802.11n AP?

2. What is the difference between 4440 and 5500 WLC for deploying 802.11n? In the specs I've only found 802.11n is optimized for 5500. I want to buy a WLC for 30 AP's and I'm not sure waht is the best option for me. I'm afraid 4400 will be soon EoL announced since 5500 have versions for the same number of APs

Thanks

jepatil Wed, 12/16/2009 - 14:58

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1. If you only have 802.11g clients, do you have more capacity for them if you use a 802.11n AP or you only can use this capacity with 802.11n clients? I mean can you connect more 802.11g clients in a 802.11n AP?

Jeevan> 802.11n AP similar to an 802.11a/g AP can technically have more than 100 clients connected to each radio at one point of time. However the experience that you receive will be diluted based on the applications that are being used, the bandwidth requirements and number of clients. The rule of thumb is that for enterprise-grade experience deploy upto 15 clients per radio or 30 clients per AP irrespective of 802.11n or 802.11a/g APs.

With the newer APs such as 1140 and 1250; there are significant advantages versus the older ones:

1.More memory(DRAM and Flash)

2. ClientLink technology enables higher downstream throughput to a/g clients

3. MRC technology enables higher upstream throughput from a/g/n clients

For more details review:

http://www.cisco.com/en/US/netsol/ns767/networking_solutions_package.html

2. What is the difference between 4440 and 5500 WLC for deploying 802.11n? In the specs I've only found 802.11n is optimized for 5500. I want to buy a WLC for 30 AP's and I'm not sure waht is the best option for me. I'm afraid 4400 will be soon EoL announced since 5500 have versions for the same number of APs

Jeevan> Similar to the AP evolution detailed above; the 5500 offers several benefits vs the 44xx:

1.      Ability to scale upto 250 APs with a software licensing model

2.      8 Gbps uplink

3.      DTLS encryption to ensure full-line-rate encryption between access points and controllers across remote WAN/LAN links.

For more details refer:
http://www.cisco.com/en/US/prod/collateral/wireless/ps6302/ps8322/ps10315/data_sheet_c78-521631.html

jcoune Thu, 12/17/2009 - 07:21

Hello,

Currently we have a customer were we want to do an upgrade from IOS ap's(1131ag and 1242ag) to 1250n and 1142n and wlc's.

The structures are very complex buildings for storage.

If we do the migration, is it a good case to just install the new ap's close to the existing one and then migrate?

Or do they have to be placed on the same position?

We need to do the migration in one day, so therefore this senario.

Greetings,

Jo

jepatil Thu, 12/17/2009 - 13:22

Hello Jo,


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They do not have to be in the exact same position but you do not want the AP antennas too far away as the new 11n APs need to cover the same cell area as the existing a/g APs do.


Regards,

Jeevan

bapatsubodh Fri, 12/18/2009 - 05:04

Hi Jeevan,

Thanks for replying my first post.

We have AP 1250 and it's radio 0 interface is enabled for operational rates from 1.0 to m15 Mb/sec. Therefore it is expected that clients will get connected at 300 mbps. I have installed latest Intel's wireless driver (wifi Link 5100 series). Intel's document also shows a snapshot of client getting connected at 300 mpbs. But I think I am missing something may be a configuration command which is required to start 802.11n on the access point.  Does our current system software version support 802.11n or we need to upgrade it to some another version.

Here are the deatils of AP.

Product/Model Number:AIR-AP1252AG-A-K9
System Software Filename:c1250-k9w7-tar.124-10b.JA1
System Software Version:12.4(10b)JA1
Bootloader Version:12.4(10b)JA

Really appreciate your guidance.

Thanks

Subodh Bapat

jepatil Fri, 12/18/2009 - 10:06

Hi Subodh,

Thanks again for reaching out on this question.

Firstly the 5100 is 1x2 MIMO so you can only get maximum of 150 Mbps downstream(AP to client) and 300Mbps upstream(client to AP)

http://download.intel.com/network/connectivity/products/wireless/319981.pdf

Secondly 150 and 300 Mbps are theoretical max rates. The typical rates that you would expect would be about half of theoretical maximum when one client is connected to one radio.

Finally please confirm that you are doing all the right configurations to optimize performance for 11n:

http://www.cisco.com/en/US/solutions/collateral/ns340/ns394/ns348/ns767/ratification_checklist_brochure_c11-557441.pdf

Best of luck,

Jeevan

jeff.kish Fri, 12/18/2009 - 08:22

Hi Jeevan,

I have a few quick questions:

Did the final draft end up banning 40MHz channels in the 2.4GHz space?

If not, does Cisco allow 40MHz channels on its 2.4GHz radios?  (not that I would ever do it, I'm just curious)

Does Cisco allow greenfield N deployments yet?  It's currently not possible to deploy a 1250 or 1140 without allowing at least one a/g rate.

Are there plans for a 1200-series 802.11n AP that runs on AF power? 

Thanks!

Jeff

jepatil Fri, 12/18/2009 - 09:13

Hi Jeff,

Here are the answers to the three questions:

1. 40MHz channels in 2.4G: Cisco APs do allow you to configure 40MHz in 2.4G. However we obviously dont recommend deploying it in that fashion anywhere other than homes, labs or secluded environments given the limited set of channels. In the final 11n standard; there was an optional feature introduced which was about protection mechanisms in 2.4G whereby if an AP operating in 40MHz detects clients in 20MHz then it has to automatically back down to 20MHz. Cisco deemed that this was really not a feature that would not be deployed by typical enterprise customers and therefore do not implement this.

2. 11n Greenfield mode: This is a feature that requires newer chipsets and therefore newer APs

3. 1200 series APs: Sorry I cannot divulge any roadmap plans in this forum. If you reach out to your Cisco account representative; I can work with them on the details.

Regards,

Jeevan

alsayed@litani.... Fri, 12/18/2009 - 10:09

Hello

i have a project with 12 AP-LAP 1552 With 2 WLC 4400,so i would like to know how would this 12 APs fits in the network?am looking for diagram scenario related to this design,i.e how these APs and The 2 WLC are phisicaly connected?Vlan things like that...

Thanks

jcartes@magenta.cl Fri, 12/18/2009 - 10:43

hi,

i have a big problem with mobility group, well i have two WLC 5500 with diferent management ip in diferent subred, so do i have one ssid, the same to the two controller but with direferent VLAN, when i do roaming to one AP asocieted to a wlc1 to a AP associeted to wlc2 this can not work i lost coenctiviti in layer 3 but am still conected in layer 2 with the AP of WLC2.

am follow all the configuration, have ping betwen WLC, the virtual ip is the same.

what can i do ?

Stephen Rodriguez Tue, 12/22/2009 - 09:02

when you look at the show moblitiy summary, do both WLC show as up?  can you mping and eping between the two WLC?

syed.raza@alltel.com Sun, 12/20/2009 - 23:25

I am installing AP 1250 with wireless clients authenticating to radius server running on MS IAS server.   The users are supposed to be authenticating with AD.  So far I have been running into problems and unable to get any user connected via Wireless LAN.

I would like your feedback if the configuration is good on the AP. Do I need to tweak it to work?   The plan is to install one and then install the rest of the 3 more APs in the infrastructure.   I would like to get the one up and running first. 


I would like any suggestion to enhance my configuration to make this work.   Also any design guidance and help for IAS configuration will be appreciated.


Config from AP


    !

    hostname cisco1-ap


    !

    aaa new-model

    !

    aaa group server radius rad_eap

     server 10.1.2.25 auth-port 1812 acct-port 1813

    !

    aaa group server radius rad_acct

     server 10.1.2.25 auth-port 1812 acct-port 1813

    !

    aaa group server radius rad_admin

    !

    aaa group server tacacs+ tac_admin

    !

    aaa group server radius rad_pmip

    !

    aaa group server radius dummy

    !

    aaa group server radius rad_mac

    !

    aaa authentication login default local

    aaa authentication login eap_methods group rad_eap

    aaa authentication login mac_methods local

    aaa authorization exec default local

    aaa accounting network acct_methods start-stop group rad_acct

    !       

 

    !

  

    dot11 ssid ABCD123

     authentication open eap eap_methods

     authentication network-eap eap_methods

     authentication key-management wpa

     guest-mode

     infrastructure-ssid optional

    !

    power inline negotiation injector installed

   !

  

    !

    bridge irb

    !

    interface Dot11Radio0

     no ip address

     no ip route-cache

     encryption mode ciphers tkip

     ssid ABCD123

     station-role root

     rts threshold 2312

     no dot11 extension aironet

     bridge-group 1

    bridge-group 1 subscriber-loop-control

     bridge-group 1 block-unknown-source

     no bridge-group 1 source-learning

     no bridge-group 1 unicast-flooding

     bridge-group 1 spanning-disabled

    !

    interface Dot11Radio1

   

    shutdown

    !

    interface FastEthernet0

     no ip address

     no ip route-cache

     speed 100

     full-duplex

     bridge-group 1

     no bridge-group 1 source-learning

     bridge-group 1 spanning-disabled

    !

    ip http server

    ip http authentication aaa

    no ip http secure-server

    ip http help-path http://www.cisco.com/warp/public/779/smbiz/prodconfig/help/eag

    ip radius source-interface BVI1

    !

    radius-server attribute 32 include-in-access-req format %h

    radius-server host 10.1.2.25 auth-port 1812 acct-port 1813 key 0 XXX-XXX-XXX-X

    radius-server deadtime 5

    radius-server vsa send accounting

    radius-server vsa send authentication

    bridge 1 route ip

    !

    line con 0

    line vty 0 4

    !

daniel.keith Wed, 12/23/2009 - 07:47

What are the future plans for upgrading the WLSE to handle the 1250N radio management? I manage roughly 450 AP's most 1210's but now we have a deployment of 60 1250's planned but now I find out the WLSE can't do radio management on them thus rendering my location manager basically useless. Can I expect a patch or upgrade soon or will I need to find another solution?

Thanks in advance,

Dan

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