Computer Science: Networking the Objective

Computer Science: Networking

The objective of this work is to examine network architecture in today's companies and to provide an explanation for various aspects of these networking systems.

"Measuring Delay, Jitter and Packet Loss with Cisco IOS SAA and RTTMON" describes the methods for measuring delay, jitter and packet loss on the data network using CISCO IOS Service Assurance Agent (SAA) and Round Trip Time Monitor (RTTMON) features and Cisco routers." It is specifically stated that the emergence of new applications on data networks makes it critically important to predict accurate the effect of the rollout of new applications. In the past allocation of bandwidth to applications was fairly easy as the applications would adapt to the rapid expansion of flows of traffic through "timeout and retransmission functions of the upper layer protocols however, voice and video as well as other "new world applications...are more susceptible to changes in the transmission characteristics of data networks." (Cisco, 2009)

Voice over IP (VoIP) is stated to be susceptible to networks behaviors which are referred to as "delay and jitter" both of which may result in degradation of the voice application to the point of being unacceptable to the average user. (Cisco, 2009) Delay refers to "the time taken from point-to-point in a network. Delay can be measured in either one-way or round-trip delay. (Cisco, 2009) It is reported that one-way delay calculations are of the nature that require expensive sophisticated test gear which are "beyond the budget and expertise of most enterprise customers." (Cisco, 2009) Measuring round-trip delay is stated to be easier and to require equipment that is less costly. It is reported that delay and jitter measurement can be accomplished through deployment of Cisco routers 17xx or higher with Cisco IOS software code version 12.05T or higher, and configuring the Cisco IOS SAA features." (Cisco, 2009)

It is reported that the routers placement should be in the "campus networks next to hosts." (Cisco, 2009) This provides statistics for end-to-end connections according to the Cisco report which states that it is not practical to "measure every possible voice path in the network then the probes should be placed in typical host locations which makes the provision of a statistical sampling of typical voice paths." (Cisco, 2009) Included in the examples are the following:

(1) a local campus-to-campus path;

(2) a local campus-to-remote campus path via a 384 kbs Frame Relay circuit; and (3) a local campus-to-remote campus via an ATM permanent virtual circuit (PVC). (Cisco, 2009)

Use of traditional phones connected to Cisco routers in VoIP deployments using Foreign Exchange Station (FXS) ports requires that the router be connected to the phones for the delay and jitter probes. Upon being deployed, the probe collects statistics and populates Simple Network Management Protocol (SNMP) MIB tables in the router." (Cisco, 2009) T

The data is then access one of two ways:

(1) through the Cisco IPM application; or (2) through SNMP polling tools. (Cisco, 2009)

Upon establishment of baseline values, SAA may be configured for sending out alerts to an NMS station if thresholds for delay, jitter and packet loss are exceeded. (Cisco, 2009 )

Yao, Kanhere, and Hassar (2008) report in the work entitled: "An Empirical Study of Bandwidth Predictability in Mobile Computing" a report of the International Conference on Mobile Computing and Networking: Proceedings of the third ACM international Workshop On Wireless Network Testbeds, Experimental Evaluation And Characterization" that while bandwidth and its predictability have been thoroughly studied in static environments "it remains largely unexplored in the context of mobile computing." In order to acquire a better understanding of what is a critical issue in the mobile environment.

Yao, Kanhere and Hassar (2008) report a study conducted over an eight-month period of measurements comprised by "...71 repeated trips along a 23Km route in Sydney under typical driving conditions. To account for the network diversity" in which measured was the bandwidth from two cellular providers identified as independent through implementation of the popular High-Speed Downlink Packet Access (HSDPA) technology in two different peak access rates (1.8 and 3.6Mbps)." (Yao, Kanhere, and Hassar, 2008)

It is reported to have been interesting that there was no significant correlation observed between the "...bandwidth signals at different points in time within a given trip. This observation eventually leads to the revelation that the popular time series models, e.g. The Autoregressive and Moving Average, typically used to predict network traffic in static environments are not as effective in capturing the regularity in mobile bandwidth. " (Yao, Kanhere, and Hassar, 2008) It is stated that while the bandwidth signal in a trip "appears as a random white noise the researchers were still able to "...detect the existence of patterns by analyzing the distribution of the bandwidth observed during the repeated trips." (Yao, Kanhere, and Hassar, 2008) It is reported that bandwidth predictability was quantified through use of the reflection of the patterns and specifically by using tools relating to information theory and specifically related to entropy.

Yao, Kanhere, and Hassar (2008) report that the entropy analysis "...reveals that the bandwidth uncertainty may reduce by as much as 46% when observations from past trips are accounted for." Further demonstrated is that "the bandwidth in mobile computing appears more predictable when location is used as a context. All these observations are consistent across multiple independent providers offering different data transfer rates using possibly different networking hardware." (Yao, Kanhere, and Hassar, 2008)

Long-Term Evolution

Long-Term Evolution (LTE) is reported to be the latest standard in the mobile technology tree "that previously realized the GSM/EDGE and UMTS/HSxPA network technologies that now account for over 85% of all mobile subscribers." (Motorola, 2009 ) The competitive edge of 3 GPPs over cellular technologies is assured by LTE. The radio access of LTE is called 'Evolved UMTS Terrestrial Radio Access Network (E-UTRAN) is expected to substantially improve end-user throughputs, sector capacity and reduce user plane latency, bringing significantly improved user experience with full mobility. With the emergence of Internet Protocol (IP) as the protocol of choice for carrying all types of traffic, LTE is scheduled to provide support for IP-based traffic with end-to-end Quality of service (QoS). Voice traffic will be supported mainly as Voice over IP (VoIP) enabling better integration with other multimedia services." (Motorola, 2009)

It is reported that initial deployments of LTE are expected by 2010" and it will be available commercially and on a larger scale." (Motorola, 2009) 3 GPP is stated to be specifying a new packet core 'the Enhanced Packet Core (EPC) network architecture to support the E-UTRAN through a reduction in the number of network elements, simpler functionality, improved redundancy, but most importantly allowing for connections and handover to other fixed line and wireless access technologies, giving the service providers the ability to deliver a seamless mobility experience." (Motorola, 2009)

The aggressive performance requirements set for LTE have resulted in a reliance on physical layer technologies including 'Orthogonal Frequency Division Multiplexing (OFDM) and Multiple-Input Multiple-Output (MIMO) systems, Smart Antennas to achieve these targets." (Motorola, 2009) It is reported that LTE main objectives are "to minimize the system and User Equipment (UE) complexities, allow flexible spectrum deployment in existing or new frequency spectrum and to enable co-existence with other 3 GPP Radio Access Technologies (RATs)." (Motorola, 2009)

Femtocells

The work of Higginbotham (2009) entitled: "Who Needs Femtocells If We Have Wi-Fi? States that femtocells are "micro-base stations placed inside the home to improve cellular coverage, are supposed to be the answer to operators' bandwidth constraints. They're also a new source of revenue for carriers and the startups and large equipment-makers who are building the devices. But so far, the market has failed to materialize, not least because consumers don't want to pay a monthly fee or buy equipment in order to help carriers improve their networks. But as Wi-Fi gets embedded on phones and hotspots proliferate, are femtocells even necessary?" (Higginbotham, 2009)

The truth is that no data services are enabled on the Femtocells and furthermore, the minutes still rack up as though the company's cell towers were being used. According to Karl Bode "...you lose minutes despite the fact you'd be reducing strain on local towers and routing calls (largely) over infrastructure Verizon doesn't own. That's either technical incompetence or maliciousness on the part of Verizon, and is the primary reason that consumers should stay far, far away." (Higginbotham, 2009)

Carrier Ethernet Compared with MPLS

According to Cisco in the work entitled: "Cisco Catalyst 6500 Series in IP/MPLS Carrier Ethernet Architecture" states that Carrier Ethernet targets two market segments:

(1) corporate; and (2) residential. (2009)

The Cisco article relates that the services which are undergoing evolution and the convergence of those providing services results in a requirement of "...a network infrastructure that has the capacity to fulfill the requirements of:

(1) scalability: offering high switching performance and bandwidth availability to support bandwidth-intensive applications and enable new sources without operational impact;

(2) flexibility: offer flexibility of port densities and various connector types with long-reach optics;

(3) Feature Richness: offer differentiators to enable metropolitan services such as MPLS, IPv6 and Multicast;

(4) Security: protect service provider resources and guarantee subscribers' traffic solution and authentication;

(5) High availability: Maximize service uptime and reduce MTTR and MTBF, through hardware redundancy, software rapid failover and subsystem In Service Software Upgrade (ISSU) with software modularity;

(6) QoS: Enable voice, video, and data on the same platform, with jitter, latency, and packet loss guarantees; and (7) Manageability: Ease service provisioning, improve operational efficiency, and reduce OpEx. (Cisco, 2009)

It is reported by Nortel that it has been indicated by 86% of service providers that there is a high demand for Ethernet services today. The result is that carriers are seeking to fulfill the demand through "upgrading their metro networks to deliver cost-effective Ethernet-based services to their customers." (2009) MPLS is stated to have been invented for the express purpose of "...of solving the problem of bridging multiple disparate protocols such as Frame Reality, ATM and Ethernet." (Nortel, 2009)