Multiplex communications – Diagnostic testing – Determination of communication parameters
Reexamination Certificate
2000-05-26
2004-12-28
Ton, Dang (Department: 2666)
Multiplex communications
Diagnostic testing
Determination of communication parameters
C370S232000, C370S235000, C370S241100, C370S248000, C375S225000
Reexamination Certificate
active
06836466
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to computer networks. More particularly, this invention relates to the measurement of network performance.
Communications systems, such as packet networks, are used in various applications for transporting data from one user site to another. At a transmission site in a packet network, data is typically partitioned into one or more packets each of which includes a header containing routing and other information relating to the data. The network then transports the packets to a destination site in accordance with any of several conventional protocols known in the art, such as Asynchronous Transfer Mode (ATM), Frame Relay (FR), High Level Data Link Control (HDLC), X.25, etc. At the destination site, the data is restored from the packets received from the transmission site.
The nature of packet switched technology, however, complicates the ability of an Information Technology (IT) manager of an end-user network to monitor the performance of a wide area network (WAN) service provider. The WAN service provider administers a WAN used for transporting data packets originating from customer premises equipment (CPE) in the end-user network across the WAN. Both the customer and the network service provider have an interest in monitoring the performance of the WAN in order to corroborate that the performance comforms with the quality of service “guaranteed” by the WAN service provider.
For example, one type of end-user network is an Internet Protocol (IP) Virtual Private Network (VPN). A VPN includes a set of Virtual Private Links (VPLs), each of which is a communication channel between two customer networks.
Network performance guarantees have emerged as a means for IT managers to ensure that their critical businesses data is delivered in a reliable, consistent manner. The term Service Level Agreements (SLA) refers to these performance guarantees. Common SLA parameters (or metrics) include packet throughput, packet loss ratio (PLR), packet delay, packet jitter, and service availability.
A Measurement Point is the boundary between a host and an adjacent link at which performance reference events can be observed and measured. A source Measurement Point and a destination Measurement Point are two Measurement Points at which packet traffic is measured. The traffic measured flows between the source and destination Measurement Points, but may originate before the source Measurement Point and may terminate after the destination Measurement Point.
The difference between the packet counts at a source Measurement Point and a destination Measurement Point divided by the packet count at the source Measurement Point for a measured interval of time defines the PLR. The service availability parameter, defined as the percentage of time that the IP service is available, depends on the PLR. One basis for the service availability function is a threshold on the PLR performance. The IP service is available on an end-to-end basis if the PLR for that end-to-end case is smaller than the threshold defined by the customer.
Packet delay is defined as the amount of time it takes for a packet to travel from the source Measurement Point to the destination Measurement Point. The differences between delays for a pair of consecutive packets that are observed at source and destination Measurement Points constitutes a packet jitter metric.
The primary objective of any service provider is to provide a quality service to its customers. Achieving a desired level of quality is not an easy task in light of the complexity of existing network environments. A network environment includes different types of equipment with different types of statistics for measuring performance, making difficult the measurement and correlation of end-to-end statistics.
Existing SLA monitoring devices monitor and collect statistics with respect to a specific technology (e.g., FR) or layer. Such devices, however, do not offer the capability of correlating IP statistics measured at two different points of an IP network that are separated by multiple lower layer networks. Knowing the SLA metrics with respect to a FR network (i.e., a WAN) is not sufficient for reporting end-to-end SLA metrics for a VPN that connects two CPE's.
FIG. 1
illustrates a network
100
, which incorporates one such SLA monitoring device. The network
100
includes two CPE's
102
and
104
, two Passive Monitors (PMs)
112
and
114
, two FR networks
106
and
108
, an IP/ATM network
110
, two routers
1000
and
1002
and a Data Analyzer (DA)
116
. As shown in
FIG. 1
, the network
100
includes clusters of technology domains (e.g., ATM, FR), which make up the paths for the VPN. The network
100
of
FIG. 1
only shows two nodes of the VPN, namely CPE
1
102
and CPE
2
104
. Each CPE
102
and
104
has an associated, distinct set of IP addresses.
A VPL is established between CPE
1
102
and CPE
2
104
, which are considered end-points of the VPN. Consequently, end-to-end network performance statistics refer to the measurement of the PLR, delay, etc., associated with packets transported from one CPE to another. Although the VPL uses a particular protocol, such as EP, for supporting communication between the two CPEs, the IP packets constituting the VPL can be transported from a CPE to another CPE via intermediate networks that use various lower layer protocols. FR networks
106
and
108
and IP/ATM network
110
exemplify such intermediary networks in the network
100
of FIG.
1
. The IP/ATM
110
network refers to either an IP network or an ATM backbone network. Routers
1000
and
1002
are used to connect the IP/ATM network
110
with the FR networks
106
and
108
respectively. The IP/ATM
10
network may include IP routers (not shown).
The PMs
112
and
114
are devices that tap into the network at two different Measurement Points, MP
A
and MP
B
, to capture FR signals. These PMs are referred to as passive monitoring devices because they collect and store the captured data without changing the packet flow.
The DA
116
is a management console that runs on a PC platform and performs analysis of the data collected by the PMs
112
and
114
. The DA
116
produces reports that include SLA metrics associated with the FR network
106
. The DA
116
bases the reports on the analysis of the collected data.
The PMs
112
and
114
tap into the FR network
106
through T1 monitoring jacks. The DA
116
is connected to each of the PMs
112
and
114
via an Ethernet network. Once the PMs
112
and
114
capture and store the FR signals, the PMs
112
and
114
send the collected information to the DA
116
.
As mentioned above, the DA
116
produces SLA reports for FR traffic statistics, as opposed to IP level traffic statistics. That is, frames are used as the basis for performance measurement, not IP packets. Although not shown, the FR network
106
is also capable of carrying non-IP traffic in the frames. Knowing the SLA metrics with respect to a FR network (e.g., FR network
106
), however, is not sufficient for reporting end-to-end SLA metrics for an IP VPN that connects two CPE locations that are on different access networks. PM
114
cannot be relocated to FR network
108
(i.e., between the FR network
108
and the CPE
2
104
) to measure end-to-end statistics based on Frame Relay information because the Frame Relay network is not end-to-end. The frames transported on the FR network
108
are not the same (i.e., they have different headers) as those transported on FR network
106
.
Although there are PMs available in the market for monitoring IP traffic (rather than just frames or ATM cells) and for enabling the DA
116
to produce SLA reports for IP level traffic statistics relevant to the performance of the VPL established between CPE
1
102
and CPE
2
104
, there still would not be any correlation of IP information at different points of the VPN. The correlation of network statistics is desirable because it allows for scalability in the network
100
. That is, correlation of statistics opens
Kant Krishna
Lau Richard C.
Siegell Bruce
Giordano Joseph
Hom Shick
Telcordia Technologies Inc.
Ton Dang
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