Wired Wireless Communication
INTRODUCTION
The architecture, development, deployment and implementation of communication technologies have come a long way. The phases of communication technologies like switching (Frame Relay, ATM, etc) and routing (IP, etc) development and deployment of these technologies and services both in the area of wired and wireless communication, and there impact in business communities always offer some kind of improvements. The essences of the push for new communication technology are for increase in efficiency and effectiveness that will improve productivity, minimize expenditure and maximize profits. MPLS is the latest communication technology that promises to bring the best of switching and routing technologies to the IP networking world. MPLS stands for Multi-Protocol Label Switching.
MPLS is a framework that allows the introduction of label switching to any combination of Layer 3 and Layer 2 protocols. In an MPLS domain, a packet is examined at the ingress point, its headers are parsed, a routing decision is made, and a label is attached to it. (Foundry Network, 2007) The packet is then forwarded to the next router and the label tells the router what to do with the packet. Hence, the switching decision is made based on the label only - not on the Layer 3 headers. The router discards the label and attaches a new label to be used by the next router. The process continues until the packet emerges at the egress point. (Foundry Network, 2007)
OVERVIEW
Today's communication networks and services are migrating to a converged paradigm centered on IP (Internet Protocol). MPLS has emerged as a key enabling technology for this migration. MPLS technology has proven its value for delivering new services while at the same time allowing migration from old to new networks. (Ixia, 2007) The rollout of MPLS brings the challenges associated with any new networking technology validating proper conformance with industry standards prior to production deployment and verifying acceptable performance. (Ixia, 2007) The development of MLS technology has ushered in a new era of Wide Area Network (WAN) technology deployment. I see MPLS as the marriage of IP routing network and frame switching network, in other word, MPLS is the union between IP routing and frame switching networks.
According to Harman H. Hopkins, (2001) “MPLS seeks to combine the flexibility of the IP network layer with the benefits conferred by a connection-oriented approach to networking. MPLS, like Frame Relay, is a label switched system that can carry multiple network layer protocols”. Similar to Frame Relay, MPLS sends information over a wide area network (WAN) in frames or packets. Each frame/packet is labeled and the network uses the label to decide the destination of the frame. (Harman H Hopkins, 2001)
BRIEF HISTORY
The development of MPLS was conceived by Internet Engineering task Force (IETF). In the mid-1990s the concept of label switching started drawing attention again, and several technologies were developed based on it, typically in the context of IP and ATM. The most notable developments were: Toshiba's Cell Switching Router, 1995, Ipsilon's IP Switch, 1996, Cisco's Tag Switching, 1996, IBM's Aggregate Route-based IP Switching (ARIS), 1996. In 1997, the MPLS working group was formed with the goal of developing a standard approach for label switching. (Foundry Network, 2007) MPLS is a network management protocol originally intended to integrate layer 2 information about network links (bandwidth, latency, utilization) into layer 3 (IP) elements within a particular system. (Knowledge Base, 2007)
MOTIVATION
Routing based on IP headers used to be performed in software, consuming many CPU cycles, and hence, performance was limited by the processing power of the CPU. Several network researchers investigated the possibility of using label switching as a means of increasing the forwarding performance in an IP network. Label switching was a much simpler function, and could be implemented in hardware, which made it a very promising approach. (Foundry Network, 2007)
Scalability of the network is a motivating force that encourages the development of MPLS technology. The vast majority of networks deployed today are based on this model, with little hard evidence to show that there is a real need for any-to-any connectivity. However, of late, propelled by the ubiquity of the Internet and by new e-business models, network designers are turning their attention to the future, with the expectation that networks may have to support any-to-any connectivity. (Harman H Hopkins, 2001)
Control over quality of service (QoS) is another driving for MPLS. To achieve a defined quality of service network resources are allocated. This ensures that when forward data is forward, it is done in a way that meets a QoS objective. Frame Relay and ATM services already provide such features at layer 2; MPLS promises to do the same for IP Internetworks. (Harman H Hopkins, 2001) Different applications require different treatment of their data. Voice and video require low delay and delay variation, but may tolerate occasional packet loss. Other data is more tolerant of delay but requires reliable end-to-end transport. MPLS helps in meeting both requirements. (Harman H Hopkins, 2001)
To provide different values for QoS or Class of Service (CoS) paths across an MPLS network is set up and allocate resources to these paths. (Harman H Hopkins, 2001) From a standardization viewpoint, MPLS can use the model developed for Integrated Services (Intserv) where RSVP (Resource Reservation Protocol) makes reservations. MPLS can also support the IETF's model of Differentiated Services (Diff-Serv) to ensure that each type of traffic receives an appropriate class of forwarding treatment (Gold, Silver, and Bronze etc.). (Harman H Hopkins, 2001)
Another driving force behind the development of MPLS is traffic engineering and the control of traffic routing. The efficient use of network resources requires control. This control is about how to ensure that the bandwidth available in a network is well used. (Harman H Hopkins, 2001) This, in turn, means that information is needed about available resources, e.g. links and the means to direct traffic over those links. In MPLS this archived by setting up explicit routes. This is in contrast to normal IP routing based on the shortest path. (Harman H Hopkins, 2001) MPLS is not designed to replace IP. Rather, it is designed to add a set of rules to IP so that traffic can be classified, marked and policed. (Knowledge Base)
BENEFITS
MPLS enables a single converged network to support both new and legacy services, creating an efficient migration path to an IP-based infrastructure. MPLS operates over both legacy (DS3, SONET) and new infrastructure (10/100/1000/10G Ethernet) and networks (IP, ATM, Frame Relay, Ethernet, and TDM). (Ixia, 2007) MPLS enables traffic engineering. Explicit traffic routing and engineering help squeeze more data into available bandwidth. MPLS supports traffic engineering prioritizing data packets. MPLS offers the tools to control the paths taken by different flows. Using these tools, traffic could be rerouted to avoid congestion points in a network. (Foundry Network, 2007) MPLS helps in Simplifying packet forwarding. Since the routing decision is made only once at the edge of the network, the core could keep only minimal routing information, thus reducing the overall complexity of the network (e.g. BGP could be run at the edge only, but there would be no need for it in the core). (Foundry Network, 2007)
MPLS supports the delivery of services with Quality of Service (QoS) guarantees. Packets can be marked for high quality, enabling providers to maintain a specified low end-to-end latency for voice and video. (Ixia, 2007) MPLS reduces router processing requirements, since routers simply forward packets based on fixed labels. MPLS provides the appropriate level of security to make IP as secure as Frame Relay in the WAN, while reducing the need for encryption on public IP networks. (Ixia, 2007) MPLS support in delivering Quality of Service (QoS) & Differentiated Services. Using MPLS' inherent mechanisms for traffic prioritization and traffic path control, a service provider could create a network that delivers QoS, facilitates offering differentiated services to customers, and fulfills the offered service level agreements. (Foundry Network)
MPLS VPNs scale better than customer-based VPNs since they are provider-network-based, reducing the configuration and management requirements for the customer. (Ixia, 2007) The reason MPLS technology is contributing to the rapid growth of the virtual private networking market is that it provides service providers and network operators with a simpler means of adding VPN technology to their portfolios, and a simpler means of provisioning VPNs to their customers. (Knowledge Base) Because MPLS allows service providers to create new virtual private networks without having to install new hardware, it significantly reduces the cost of implementation, which in turn reduces the overall cost of VPNs. Since MPLS provides tunneling of packets from an ingress point to an egress point, VPN applications that leverage this capability can be created easily. (Foundry Network, 2007)
Reduced cost is possibly the largest motivator in the migration from more infrastructure-heavy private networking. (Knowledge Base) While most of the benefits of MPLS lie on the service provider side of the network, there are results of the MPLS architecture that have direct benefits for the customer. MPLS-based service provider edge equipment is designed to communicate with customer premises equipment (CPE) in a standards-based environment, removing the need for customers to deploy new equipment, and protecting CPE investments. (Knowledge Base) MPLS also gives the service providers unprecedented efficiency, lowering their costs, which in turn is passed on to their customers. The flexibility of service, potential for higher performance guaranteed, and the lowered costs all play to the mandates for business to do more with less. (Expand Network, 2006)
OPERATIONS
MPLS-equipped networks use MPLS-aware devices known as label edge routers (LERs), positioned at the network's edges. These devices are designed to inspect IP packets entering the network and add MPLS headers, as well as removing the headers from packets leaving the MPLS network. Inside the boundaries of the MPLS network, devices known as label switch routers (LSRs) look for an MPLS label on each packet that passes through them, looking up and following the instructions contained in those labels, routing them based on a list of instructions. (Knowledge Base)
MPLS allows administrators to define routes known as label switched paths (LSPs) from one LER to another, through a series of LSRS, across the MPLS network. These LSPs are pre-assigned and pre-engineered paths that packets with a certain label should follow. (Knowledge Base)
MPLS label switching is that it allows routers to make forwarding decisions based on the contents of a simple label, rather than by performing a complex lookup based on a so-called destination IP address. In an MPLS network, incoming packets are assigned a "label" by a router. Packets are forwarded along a label switch path where each router makes forwarding decisions based solely on the contents of the label. At each hop, the label is stripped off and a new one is added that tells the next router how to forward the packet. (Marguerita, Readon, 2004)
MPLS vs ATM and FRAME RELAY
MPLS brings the label switching and traffic engineering functions of ATM to packet-based networks. MPLS, unlike ATM, runs over any Layer 2 infrastructure, i.e., it is not tied to a certain technology, which allows its use in a heterogeneous environment. (Foundry Networks, 2007) There are several flavors of layer 2 MPLS services, but what they have in common is that a Layer 2 packet (or ATM cell or frame relay frame) is encased in an MPLS header and forwarded through the MPLS core. Layer 2 MPLS services effectively extend services such as Ethernet or frame relay across an IP WAN. (Johna Till Johnson, 2007)
In many ways, the label switched paths of MPLS are no different than circuit-switched paths in traditional telecommunication technologies such as ATM (Asynchronous Transfer Mode) or Frame Relay networks. The main difference is that MPLS paths are not dependent on a particular transport technology. This means that MPLS can be used with any transport technology including ATM, Frame Relay or Ethernet. Because MPLS can separate traffic into different tunnels, carriers can use it to provide VPN services. Carriers already offer point-to-point VPNs using Frame Relay, ATM and IPSec, an IP-based encryption and tunneling mechanism. MPLS will allow them to offer a new meshed service. (Marguerita Reardon, 2004)
TYPES OF MPLS
The version of MPLS that's generally used to encapsulate connection-oriented frame relay and ATM services is called pseudo Wire Edge to Edge Emulation (PWE3). PWE3 defines point-to-point tunnels across the MPLS backbone, and thus works well for circuit-oriented networking protocols. PWE3 can also be used to support connectionless LAN protocols, but it's not the preferred solution. (Johna Till Johnson, 2007) For connectionless protocols (primarily Ethernet) there's a different specification, called virtual private LAN service (VPLS). VPLS addresses some of the specific challenges with extending Ethernet across the metropolitan area or WAN, most notably scalability and availability. Another emerging spec is the ITU's transport-MPLS (T-MPLS), which is designed to simplify deployment of Ethernet services. Finally, a variant of MPLS called Generalized Multiprotocol Label Switching (GMPLS) gives routers the ability intelligently signal the optical layer, enabling providers to establish, change or tear down optical links in real time. Thus, service providers can provision "optical wavelength" services based on MPLS. (Johna Till Johnson, 2007)
Challenges
Ixia (2007) argues that MPLS has made significant progress over the last few years and is well into mainstream deployment in networks around the world. But key challenges to attaining more widespread acceptance remain. MPLS encompasses a wide range of functionality and applications; therefore its implementation has an associated high level of complexity. Vendors, who develop MPLS technology, as well as organizations looking at deploying MPLS in a network today, must also factor in MPLS's continually evolving state and its impact on network performance and scalability. MPLS is not a standalone technology; it is overlaid on Layer 2 technologies such as Ethernet or ATM, and must operate in conjunction with other control plane protocols, such as IP routing. The complexity of MPLS deployments is increased because of this interaction. In some cases, four or more protocols may be involved in a given network scenario, necessitating careful coordination and validation of the end-to-end system. Integration of legacy services and deployment of new services, such as VPNs, requires tunneling, which in turn increases the setup requirements for a given circuit. (Ixia) The evolving of MPL technology is a continuous process which is applicable to all other technologies. According to Ixia, MPLS continues to evolve rapidly. Today, a number of extensions to the MPLS protocols, as well as new functionality, are under development. New developments often obsolete older ones. This constant development and improvement of MPLS technology cause some kind of fear on the side of vendors and service providers.
CONCLUSION
I strongly believe that MPLS technology has come to address the issues that are associated with switching and routing technologies. The development, deployment and implementation of MPLS helps to combine the benefits of connectionless layer 3 routing and forwarding with connection-oriented layer 2 forwarding. MPLS being technique not service support the delivery of anything from IP VPN to Metro Ethernet services and optical services. Based on my research, I believe the introduction of MPLS technology into today's communication technologies will help in achieving business continuity in a higher dimension and improve productivities scale. MPLS is the latest technology in the era of communication and Internet networking to effectively and efficiently improve packet-forwarding, supports Qos and Cos for service differentiation, support network scalability, integrates IP, ATM and frame relay into one network and build interoperable networks that will help vendors and service providers to provide better services. All these functionalities will eventually help businesses to cut cost in the deployment, implementation, operation and maintenance of this wonderful technology and maximize profits.
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