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Optical/IP Networks

Testing Cisco's Mobile Core, Data Center & Business Services

Earlier, Light Reading published the first part of the massive independent test of Cisco Systems Inc. (Nasdaq: CSCO)’s next-generation mobile network infrastructure. (See Testing Cisco's Next-Gen Mobile Network and LR & EANTC Test Cisco’s Mobile IP Network.) Even in a one-minute video montage you can get a sense of the sheer size of this project:

This article is the second feature highlighting the results of this enormous test. Before we get to the background and test setup, here's a hyperlinked table of contents for this special feature:



Background
Our testing team of the European Advanced Networking Test Center AG (EANTC) spent four weeks at Cisco's labs, validating the solutions presented to us. A key component we wanted to see in action is the mobile core. This is the logical data center area where the operator positions all the central packet and voice gateways, auxiliary control plane systems required to run the mobile network, plus consumer and business application servers.

At the beginning of the project late last year, we really scratched our heads when Cisco announced their willingness to join our test. How would they provide all the mobile core equipment? Of course, a search for SGSN on Cisco’s Website resulted in zero hits back then. But when Cisco bought the ASR 5000 (acquired from Starent Networks Inc.) it added a single specialized hardware platform that implements the voice and packet gateway functions both for 3G and Long Term Evolution (LTE).

UMTS voice and packet gateways have served their purpose in the industry quite well in the past years. Our test comes at a moment when things are changing rapidly. The major current challenges of mobile operators include:

  • Mobile data growth: Mobile subscribers expect multi- Mbit/s (megabits per second) throughput, through high-speed packet access (HSPA). All this traffic needs to transit the serving gateways and packet gateways. Performance requirements are much higher than before, and a large and growing fraction of subscribers has access to smartphones and other end systems capable of high-speed data. (See Cisco: Video to Drive Mobile Data Explosion.)
  • Migration to LTE, where the mobile core is called Evolved Packet Core (EPC): The drastic changes from 3G to LTE affect base stations, air interfaces, and backhaul networks. The LTE mobile core needs to grow to keep pace with the huge air interface bandwidth extensions, and it needs to support the all-IP radio access network (RAN) by providing suitable application policies, for example to differentiate operator-provided voice over IP and bulk data traffic.
  • Monetization: The mobile core is the key area where decisions are made to prioritize applications associated with revenue and to throttle bulk applications that just take away frequency spectrum and backhaul capacity (such as P2P, file sharing, etc.). The goal for mobile operators is to avoid too much precious spectrum being taken by applications that do not generate revenue.


This requires that vendors have an idea of what applications could generate revenue – certainly not a trivial question, and not to be answered unanimously across all subscriber bases worldwide. Cisco showed us some of its ideas – see the Mobile Smart Home demonstration on Page 12.

Another note on LTE: How far have implementations matured? The industry has been buzzing with success stories in press releases. But outside four city areas serviced by Telia Company , no LTE network of any scale has started production-grade services yet. Many mobile operators are testing the technology and most operators plan to deploy LTE only after 2012. We checked how well Cisco would be prepared for LTE with their mobile core offerings now. And recall that we tested its LTE backhaul design in the previous testing article. (See Testing Cisco's Next-Gen Mobile Network.)

Test setup
The test scale was phenomenal, even to previous EANTC and Light Reading standards. Our Spirent Communications plc contacts were surprised when they heard our requirement to fully emulate beyond 1 million mobile handsets for voice and data traffic. They had to bring in eleven of their fastest and largest Landslide mobile network emulators. The Landslides emulated the user equipment (UE) – like the cellphones and mobile data cards – and the data aggregation/transport aspects of the emulated base stations.

Due to emulator limitations, we agreed that Spirent would configure 16 artificially large base stations in this test, each of which emulated 62,500 subscribers. We counted only registered and attached subscribers toward this figure.

In real life, only roughly one-in-five to one-in-ten consumer phones is on a voice call at any time. Today, with still a lot of prepaid, voice-only phones around, probably even fewer subscribers are actively exchanging data traffic. A noticeable fraction of customers with a contract or prepaid card might even switch off their phones. Each of these factors would have blown up the numbers – in an artificial, unrealistic way. Therefore we abstained from any of such statistical “improvements” and counted only real, attached subscribers.

The Landslide emulators were connected – through the network set up in the previous phase – to three ASR 5000’s, taking 3G and LTE roles in turn. They were reconfigured from 3G to LTE after the first set of test cases had been completed. Since we required such a large farm of Landslides with 20x10G and 10xGE ports, we ended up using one of the Nexus 7000 switches to aggregate all the tester ports so we could reach the performance we intended to generate for the SGSN, GGSN, and EPC tests. This choice is reflected in the figure above.

For each subscriber, we emulated a range of application flows such as Voice over Internet Protocol (IP), HTTP, plain Transmission Control Protocol (TCP), and UDP data. All flows were IPv4-based in the Landslide/ASR 5000 tests. Since we required such a large farm of landslides with 20x10G and 10xGE ports, we ended up using one of the Nexus 7000 switches to aggregate all the tester ports so we could reach the performance we intended to generate for the SGSN, GGSN, and EPC tests. This choice is reflected in the figure above.

In addition, we required auxiliary mobile core functions to complete the scenario:

  • The Home Location Registrar (HLR) in the 3G world was provided by an emulator from Developing Solutions, a Texas-based specialist test vendor for mobile core component emulation.
  • The HLR’s equivalent in the LTE world, called Home Subscriber Server (HSS), was provided by Bridgewater Systems Corp. (Toronto: BWC). In addition, to ease and speed up scalability testing, we used the Developing Solutions emulator for the HSS function in parallel as well. All tests involving an HSS were carried out twice – with the emulator and the production system.
  • Finally, a Policy Charging and Rules Function (PCRF), also supplied by Bridgewater, was required to interface with the main packet gateway. The PCRF takes decisions on behalf of the packet gateway – anything that requires looking up per-subscriber rule-based behavior. A PCRF configuration can get quite advanced, and could be a competitive differentiator for a mobile operator. Since this equipment was not the major topic of the test, we kept it as trivially configured as possible. Its only purpose was to keep pace with our performance and scalability tests.

In this huge scenario, we evaluated a total of five test cases and two vendor demonstrations. Let’s see the details.

— Carsten Rossenhövel is Managing Director of the European Advanced Networking Test Center AG (EANTC) , an independent test lab in Berlin. EANTC offers vendor-neutral network test facilities for manufacturers, service providers, and enterprises. Carsten is responsible for the design of test methods and applications. He heads EANTC's manufacturer testing, certification group and interoperability test events. Carsten has over 15 years of experience in data networks and testing. His areas of expertise include Multiprotocol Label Switching (MPLS), Carrier Ethernet, Triple Play, and Mobile Backhaul.



Jambi Ganbar, EANTC, managed the project, executed the IP core and data center tests and co-authored the article.

Jonathan Morin, EANTC, created the test plan, supervised the IP RAN and mobile core tests, co-authored the article, and coordinated the internal documentation.


Page 2: Results: ASR 5000 SGSN Attachment Rate

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cross 12/5/2012 | 4:24:02 PM
re: Testing Cisco's Mobile Core, Data Center & Business Services

Hi 2skhatri,


For this test, the maximum number of simultaneously attached users to the GGSN (and by coincidence in a separate SGSN test as well) was one million.


We spent quite some time with Heavy Reading analysts and Cisco network design experts to come up with realistic scalability goals.&nbsp; Our goal was to balance between a vendor view (larger is better and more competitive) and a realistic view (what are service providers likely to ask for in the next few years?).


We determined the GGSN / SGSN scalability test goals based on population density factors.&nbsp; How many subscribers will live in a certain geographic region covered by a single GGSN / P-GW?&nbsp; How many subscribers are likely to be serviced by the same base station?&nbsp; How many of those will use 3G HSDPA data services at the same time?


We also took operator goals into account, specifically high availability, latency caused by distance, and the avoidance of a single point of failure in general.&nbsp; What will be the maximum distance of an SGSN from the base station?&nbsp; How many independent mobile core sites will a reasonably large operator require to minimize any operational risks?


This is how we got to one million.


Thanks Carsten


&nbsp;

tohhwee72 12/5/2012 | 4:23:59 PM
re: Testing Cisco's Mobile Core, Data Center & Business Services

Hi Carsten,


Seems like the testing is not really for a mobile network.


1. Majority of the packects in a mobile network&nbsp;are less than 512 bytes. To be exact, l have seen operators having more than 50% of the packets less than 128 bytes. This will have a impact on the firewall performance. Large packet is something very rare in a mbile network.


2. The test is&nbsp;for a mobile network environment, should not make reference to a enterprise network.&nbsp;A 1:1 NAT&nbsp;will not happen for a mobile network, even&nbsp;for a large enterpeise network.&nbsp;Hence, l seriously doubt the firewall can achieve 1 mil concurrent connections when operators has only a few public IP address for NAT.


These are just some of my observation.


Regards,


Toh Hwee

packetera2 12/5/2012 | 4:23:49 PM
re: Testing Cisco's Mobile Core, Data Center & Business Services

Are these numbers tested indicate the maximum what ASR5000 can support? I mean 20Gbps of throughput and for DPI only enabling bittorrent traffic interceoption for single user doesn't give real performance capabilities.....


any comments?

Yossika 12/5/2012 | 4:23:34 PM
re: Testing Cisco's Mobile Core, Data Center & Business Services

&nbsp;


Hi,


&nbsp;


According to the numbers (CPU utilli&nbsp;)&nbsp;you didn't reach 50% of the Node capbilties??


&nbsp;


Was wondering if you did the same test with SPI L3 L4 only??


&nbsp;

JeddChen 12/5/2012 | 4:23:12 PM
re: Testing Cisco's Mobile Core, Data Center & Business Services

Hi, Carsten,


&nbsp;


Thank you for your very detailed clarification. that's helpful

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