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Routing

Testing Cisco's Next-Gen Mobile Network

Summary: Here we demonstrated that the ASR 9010 and 7609 platforms could appropriately classify and prioritize five classes of traffic during link congestion.

In designing this network, Cisco had an easier task than when normally planning live networks: The users were emulated, and thus their network usage was static instead of bursty. The network was appropriately built to accommodate for this usage and did not experience congestion. In real-world practice, however, network areas will have both usage peaks and plateaus.

Specifically, base station locations are typically provisioned for peak usage – to handle the maximum load of users – however the backhaul network is typically not. The base station requirement comes from the reality of human location. In the case of events such as a sports event or concert, hundreds of users will be concentrated for a few hours.

Now you might say you have attended a large sports event before and never had issues with voice calls. Correct: The issue is primarily related to data traffic amalgamating the live experience at a growing rate. A few parallel video streams may saturate a single base station. Sure, outside of these hours, the local network resources may not be used much at all, however during an event if too many calls are lost or there is no connectivity, it would be a pretty negative experience for the user.

But to plan for full load throughout the aggregation and core networks is simply not worth the cost. Some routers can be saved with the cost of a few rare moments of congestion. For these rare moments, though, a crucial and well known feature is incorporated into packet backhaul networks: Quality of Service (QoS).

As a side note, LTE is designed with smart advanced mechanisms to circumvent network congestion during such usage peaks at the application layer by redirecting base station traffic – but the practicality of these mechanisms has not been widely tested yet to our knowledge, and they are not available for 2G and 3G networks anyway.

QoS describes the general ability to differentiate traffic and treat it differently in regard to its drop priority, drop probability, increased or decreased latency, and so on. The goal in this test was to verify that in a congestion scenario, the DUT would prioritize traffic accordingly. To prove that such prioritization could work in a realistic scenario, we used the master traffic configuration explained earlier on. In order to create congestion, we removed a single link in the network. We performed the test on two systems: Cisco’s ASR 9010 and 7609.

Table 4: Qos in the IP-RAN: 7609
Traffic Class Mobile Generation Application Type Application Sample Direction Percent Packets Lost from this Class (all streams) Percentage of Streams from this Class with Loss Average Percentage Loss Amongst Affected Streams
Best Effort 2G (data) - 3G (ATM data) Background all data UE� --> ME�� No Loss No Loss No Loss
Best Effort 3G - LTE Background SMS, email, downloads ME --> UE 2.79% 13.20% 26.13%
Assured Forwarding (cs2) 3G - LTE Interactive Web browsing, data base retrieval, server access UE --> ME No Loss No Loss No Loss
Assured Forwarding (cs2) 3G - LTE Interactive Web browsing, data base retrieval, server access ME --> UE No Loss No Loss No Loss
Expedited Forwarding 2G (TDM) Real time-user all data UE --> ME No Loss No Loss No Loss
Expedited Forwarding 3G (ATM) - LTE Real time-user voice, control ME --> UE No Loss No Loss No Loss
Assured Forwarding (cs4) 3G - LTE Streaming multimedia, video on demand, Webcast applications ME --> UE No Loss No Loss No Loss
Assured Forwarding (cs4) 3G - LTE Streaming multimedia, video on demand, Webcast applications ME --> UE No Loss No Loss No Loss
Expedited Forwarding (cs5) LTE Real time-network X2 Interface SideA -> SideB No Loss No Loss No Loss
* User Equipment
** Mobile Equipment


In preparation for the test, we found that Cisco’s hash algorithm for load balancing on the 7609 and ASR 9010 works unevenly. This is a generic issue with hash algorithms across the industry – in Cisco’s case, though, some links were loaded at only 29 percent of line rate, while others were heavily used at 71 percent. We allowed Cisco to show us which links were under heavier load, guaranteeing that their removal would induce congestion on the router. In each case, links between similar device types were removed – between the 7609 connected to the aggregation ring and the 7609 connected to the PTP Grandmaster, and between the upstream ASR 9010 and downstream ASR 9010.

QoS Test Topology: Cisco 7609 QoS Test Topology: Cisco ASR 9010 Once the link was chosen, it was calculated that in the ASR 9010 test the three lower classes would suffer from congestion, and in the 7609 test only one class (BE, Best Effort) would. This meant that zero packet loss was expected on any of the top three, or four, classes, respectively. The results were pretty straightforward. In the ASR 9010 test, we in fact saw zero packet loss on our top three classes (EF, CS4, CS5) and saw a decent percentage of loss, but not everything, occurring on the lower two priority classes (CS2, BE). In the 7609 test there was enough bandwidth for the top four classes to get through without loss, and only BE traffic observed loss.

Table 5: Qos in IP-RAN: ASR 9010
Traffic Class Mobile Generation Application Type Application Sample Direction Percent Packets Lost from this Class (all streams) Percentage of Streams from this Class with Loss Average Percentage Loss Amongst Affected Streams
Best Effort 2G (data) - 3G (ATM data) Background all data Upstream No Loss No Loss No Loss
Best Effort 3G - LTE Background SMS, email, downloads Downstream 7.59% 5.02% 99.15%
Assured Forwarding (cs2) 3G - LTE Interactive Web browsing, data base retrieval, server access Upstream No Loss No Loss No Loss
Assured Forwarding (cs2) 3G - LTE Interactive Web browsing, data base retrieval, server access Downstream 0.32% 8.33% 2.67%
Expedited Forwarding 2G (TDM) Real time-user all data Upstream No Loss No Loss No Loss
Expedited Forwarding 3G (ATM) - LTE Real time-user voice, control Downstream No Loss No Loss No Loss
Assured Forwarding (cs4) 3G - LTE Streaming mulimedia, video on demand, Webcast applications Downstream No Loss No Loss No Loss
Assured Forwarding (cs4) 3G - LTE Streaming mulimedia, video on demand, Webcast applications Downstream No Loss No Loss No Loss
Expedited Forwarding (cs5) LTE Real time-network X2 Interface Between eNodeBs No Loss No Loss No Loss


Page 6: Route Processor Redundancy

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DevilsRejection 12/5/2012 | 4:25:15 PM
re: Testing Cisco's Next-Gen Mobile Network

I just spent a good 30 minutes reading this, twice, and am still digesting it. Can't wait for part 2. Will you be offering an easy to digest PDF to make sharing this around the office easier?


Thanks!

DevilsRejection 12/5/2012 | 4:25:14 PM
re: Testing Cisco's Next-Gen Mobile Network

Looking forward to it!


I have to admit that the first run through was a quick skim to see if a more thorough reading was worthy of my time. The second reading is where I focused. Skipped the charts, relied on the heavy text descriptions.


Been a heavy reader since as far back as I can remember. I'm fast! ;-)

DCITDave 12/5/2012 | 4:25:14 PM
re: Testing Cisco's Next-Gen Mobile Network

Thanks. We'll post a link to a PDF once we're through making some minor tweaks (and adding a couple of photos of the testing dungeon).


Quick question: How'd you get through this thing in just 30 mins? It's a beast.

miusuario 12/5/2012 | 4:25:10 PM
re: Testing Cisco's Next-Gen Mobile Network

Article is very extensive and interesting. I was specially interested in the QoS techniques that were tested, and couldn't really understand exactly the scope. Most of these tests should be done with Radio and backhauling, as there is were congestion relies. At the moment this seems limited, so please include more details.


Also, name of the article should better be "Testing Cisco Core Solution for Mobile Networks". As the equipment involved is far from being a complete Mobile Network.

JeddChen 12/5/2012 | 4:25:09 PM
re: Testing Cisco's Next-Gen Mobile Network

A heavy-weighted player is entering the muddy water of Core network solution.

cross 12/5/2012 | 4:25:07 PM
re: Testing Cisco's Next-Gen Mobile Network

Hi miusuario,


Thanks for your review and kind words.  You raise a good point about testing a complete mobile network: This is only the first of two articles - the second article, focusing the REAL mobile core (GGSN, SGSN, LTE P-GW/MME), mobile applications and the mobile operator's data center will be published after labor day next week. Stay tuned!


With regards to QoS, I certainly agree - congestion is most likely and critical in the backhaul.  We tested QoS on the ASR9010 and 7609 routers. Both routers were loaded with application traffic types in five classes (Expedited Forwarding; Assured Forwarding cs5/cs4/cs2; Best Effort).  Under congestion we expected them to only lose Best Effort traffic (7609) and BE + cs2 traffic (ASR9000), respectively.  The test was passed.  For more info please see Page 5 of the report.


Thanks! Carsten

bbiswas 12/5/2012 | 4:24:34 PM
re: Testing Cisco's Next-Gen Mobile Network

Hello Carsten:


Thanks to the very informative posting. Although I did not understand some of the things your lab is doing but it was interesting to know about them.


I would be intrested to know about EANTC's activities in the LTE EPC Core testing. Do you have any LTE network set up in your lab with UE's, ENB, MME, SGW, PGW etc ?


Thanks and regards,


Bud Biswas ([email protected])


Polaris Networks (www.polarisnetworks.net)

harindha 12/5/2012 | 4:22:16 PM
re: Testing Cisco's Next-Gen Mobile Network

It's really interesting to know that CRS-1 to CRS-3 upgrade was very smooth.


I think you upgrade the router to IOS-XR 4.0 first and then swap the new fabric with old fabric one by one ?


is the above assumption correct ? or do we have any restriction on the ROMMON versions on the existing modules ?

harindha 12/5/2012 | 4:22:06 PM
re: Testing Cisco's Next-Gen Mobile Network

Thanks Carsten, for your effort on getting this clarrified.


Rgds


Harin

ar_salem 12/5/2012 | 4:22:06 PM
re: Testing Cisco's Next-Gen Mobile Network

Dear Carsten,


Your article is really interesting. Can I have a PDF version of total of article?


Thanks, Alireza

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