Publication Date: June 12, 2000
Preliminary Test Plan
v. 1.0. Copyright © 2000 by Network Test Inc. Vendors are encouraged to comment on this document and any other aspect of test methodology. However, Network Test reserves the right to change the parameters of this test at any time.
This document describes the procedures to be used in comparing devices with bandwidth-management capabilities. Products will be evaluated in four areas: ease of configuration/management; performance; features; and co-existence with other QOS devices or mechanisms. Relative weighting of each category are as follows: configuration/management, 25 percent; performance, 40 percent; features, 25 percent; co-existence with other QOS devices/mechanisms, 10 percent.
The general goal of this test is to determine whether bandwidth managers ensure that high-priority flows (translation: those carrying revenue) always fall within acceptable latency/response time or throughput boundaries. One area of special interest is determining how well these devices enforce traffic management contracts on low-bandwidth WAN links and/or links used by large numbers of users.
To benchmark device performance, independent consultancy Network Test (Hoboken, NJ) has teamed up with Netcom Systems Inc. (Calabasas, Calif.) to develop a new test application for bandwidth managers. As with prior tests, the new application runs on Netcoms Smartbits traffic analyzer. Unlike previous applications, the new application runs stateful TCP connections. In this test, we plan to offer up to 200 concurrent TCP connections, even through low-bandwidth T1 (1.5-Mbit/s) circuits.
1. Ease of configuration/ease of management
Lab personnel will grade each device, on a 1 to 5 scale (where 5 = excellent and 1 = poor), on ease of accomplishing each of the following tasks.
2. Performance tests
There are four tests of performance: baselines, forwarding rate, latency, and mixed-class forwarding rates.
Each of these four tests will be run twice, with each iteration modeling a different scenario where bandwidth managers might be used. Vendors are free to participate in either or both scenarios; there is no penalty for electing not to participate in both scenarios.
Scenario 1 models a branch office with 200 users. A single T1 (1.5-Mbit/s) circuit provides all Internet connectivity.
Scenario 2 models a server farm run by a content hosting service. In this case, a customer of the service is allocated a 100-Mbit/s circuit to handle traffic to and from its customers servers.
All tests will be conducted via 100Base-T physical interfaces; we will rate-control the offered load for the T1 tests.
As in the configuration/management tests, the device under test will use 10.0.1.254/24 on its local interface and 220.127.116.11/24 on its external interface. If the device operates as a bridge, the second interface should be 10.0.1.253/24.
a. Baseline tests
Objective: To determine each devices basic traffic-handling capabilities before bandwidth management is enabled.
Procedure: Offer line-rate loads of 64- and 1518-byte UDP packets to each device in both unidirectional and bidirectional flows.
b. TCP rate enforcement
Objective: To determine the ability of the device under test to guarantee specific amounts of bandwidth to high-priority flows.
Procedure: Configure device to allocate 512 kbit/s (for T1 tests) or 30 Mbit/s (for 100-Mbit/s tests) for high-priority flows.
Offer up to 200 concurrent HTTP 1.0 requests to each device, plus enough background UDP traffic to present an aggregate load of 150 percent of line rate, thus creating congestion. Of the 200 HTTP requests, 20 are high-priority flows. (This type of 10/90 split models traffic at an e-commerce site, where 90 percent of requests represent customers surfing around and 10 percent are placing orders.)
Verify that high-priority requests get the 512 kbit/s or 30 Mbit/s reserved for them, but not more.
Stop all traffic generation, and restart with low-priority HTTP 1.0 requests only. Verify that the low-priority sessions are able to use the bandwidth available, including that previously reserved for the high-priority flows. (This step verifies that the bandwidth managers dont use static, TDM-like bandwidth reservation.)
c. TCP latency enforcement
(Note: Not all devices can enforce latency bounds. This test will only be run on those devices supporting such capability.)
Objective: To determine the ability of the device under test to enforce specific latency boundaries.
Procedure: Configure device to ensure that response time for high-priority HTTP 1.0 GET requests never rises above 500 milliseconds, and never above 2,000 ms for low-priority HTTP 1.0 GET requests.
Offer up to 200 concurrent HTTP requests to each device, plus enough background UDP traffic to present an aggregate load of 150 percent of line rate, thus creating congestion. Of the 200 HTTP requests, 20 are high-priority flows. (This type of 10/90 split models traffic at an e-commerce site, where 90 percent of requests represent customers surfing around and 10 percent are placing orders.)
In this test the background load will consist of 1,518-byte frames and the HTTP requests will be for large objects, also forcing a predominance of 1,518-byte frames. This combination of long frames and congestion will force latency to rise, and thus creates a stressful environment for evaluating latency shaping. For bandwidth managers that rely on queuing, long frames mean longer intervals before the device can service packets in each queue. For bandwidth managers that rely on tuning the TCP window sizes, the overload of traffic should force the device to reduce window size in an effort to reduce congestion.
Verify that high-priority requests are serviced within 500 ms, as per device configuration.
Stop all traffic generation, and restart with low-priority HTTP 1.0 requests only. Verify that low-priority requests are serviced within 2,000 ms, as per device configuration. Restart high-priority requests and observe both high- and low-priority latency measurements. Withdraw high-priority flows once again. Measure interval between withdrawal of high-priority flows and the point where low-priority flows once again are serviced within 2,000 ms.
d. Mixed-class traffic handling
Objective: To determine the ability of devices to define enforce multiple priority levels while concurrently handling TCP and UDP flows.
Procedure: Configure device under test to allocate bandwidth in a 3:2:1 ratio to high-, medium, and low-priority flows. The high-priority traffic of UDP packets on port 111 (portmap). The medium-priority traffic will consist of HTTP 1.0 get requests and responses with URL B. The low-priority traffic will consist of HTTP 1.0 get requests and responses with URL C.
Offer approximately 50 Mbit/s of each priority class to the device under test, thus creating an overload of 150 percent.
To conform with the 3:2:1 ratio:
--the device will forward all of the high-priority traffic without loss
--the device will drop about 1/3 of the medium-priority traffic
--the device will drop about 2/3 of the low-priority traffic
3. Features comparison
To assemble a table comparing device features, participating vendors will answer the following questions:
What types of physical interfaces does the device support?
What is the maximum number of physical interfaces the device support?
Does the device support definition of multiple virtual interfaces on a singe physical interface?
What criteria does each device use to classify traffic, and why?
--URL/cookie (new feature, and only on some devices)
--application signature (new feature)
--voice over IP identifiers like RTP headers (new feature)
--TCP/UDP port numbers
--IP precedence field
--IP source/destination address
What type of bandwidth enforcement mechanism does the device use?
--TCP window control
What is the cost of the device as tested?
4. Coexistence with other QOS devices
Given the growing importance of QOS and policy management in enterprise and service provider networks, integration with other QOS devices may be a requirement. No formal testing of integration/interoperability with other devices is planned. However, vendors will be asked to describe how their devices interoperate with policy servers, directory servers, or other pre-existing QOS mechanisms.