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Multiprotocol routers are the Swiss army knives of enterprise networking, but how does the value proposition change as the world moves to end-to-end IP and Ethernet? Routers route, and routing is a fundamental requirement of any packet network. Routing takes place at Layer 3 — the level at which end-to-end addressing takes place. This addressing structure is hierarchical (much like telephone numbering),
which makes routing tenable. Routing consists of two closely related functions, the act of determining routes to various destinations through routing protocols such as Open Shortest Path First (OSPF), and the act of forwarding packets to the next best hop (or hops in the case of multicast). Routers are required to provide routing between physical or logical LAN segments; within a given LAN, the broadcast nature of the LAN is leveraged to dynamically learn which IP addresses are locally reachable.
Routers also support traffic management functionality over the WAN with the dual (and somewhat conflicting) objectives of maximizing network utilization under various traffic and failure conditions, and meeting end user and application needs. These objectives are met through various queuing functions to ensure fair treatment of users and maximum aggregate throughput, and through various QoS mechanisms that provide unfair treatment of users and applications. Packet classification, shaping, and policing are some of tools of the trade. Approaches towards traffic management continue to evolve. Multiprotocol Label Switching (MPLS) in the core introduces virtual connections somewhere between Layer 1 and Layer 2, which make traffic management easier and provide new mechanisms for segregating traffic by users or other attributes.
So routing is here to stay, though the implementations are becoming more hardware intensive, more specialized, and increasingly integrated with optical networking. In addition, specialization has routing functionality being incorporated into devices that are optimized for specific needs including campus switches and VPN appliances.
ROUTER NETWORK COMPLEXITY
Router networks today present significant challenges to IT managers. This is largely driven by the heterogeneous nature of enterprise networking. Attracting, training, and retaining IT skills is an on-going concern. This heterogeneity is caused by multiprotocol operation, by multiple LAN technologies, and by proliferation of WAN services.
It’s been a multiprotocol world with enterprise networks required to support different protocols for different application environments: e.g., IBM’s SNA for mainframe environments, IP for UNIX, IPX for Novell, and DECnet for legacy Digital Equipment (now Compaq) systems. Each of these had its own networking and routing protocols, and idiosyncrasies (e.g., IPX is notoriously chatty).
It’s been a multi-LAN technology world with enterprises having deployed Ethernet, token ring, FDDI (Fiber Data Distribution Interface), and ATM, and with some sites having all of these. Token ring was driven by IBM and has been widely deployed in mission-critical (e.g., bank branch) environments with its highly predictable behavior and reliability. FDDI was the first fiber-based backbone LAN technology supporting highly reliable 100 Mbps operation, at a time when desktops ran at 10 and 16 Mbps, for Ethernet and token ring respectively. ATM, particularly supporting ATM LAN emulation, provided further scalability via high-capacity switching and campus backbone links at speeds up to 622 Mbps. Routers not only had to support the physical LAN media which required a range of copper, coax, and fiber interfaces, but also had to support the Media Access Control (MAC) functionality specified for a specific type of LAN technology. In addition, they also supported higher level gateways to these LAN environments. For example, routers adapted IBM traffic running on token ring LANs to IP via Data Link Switching (DLSw), or emulated Ethernet or token ring environments when interfacing to ATM campus backbones.
It’s been a multi-WAN technology world. Routers encapsulate packets onto lower speed WAN services:
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Dedicated point-to-point circuits; e.g. , running point-to-point protocol (PPP) over private lines.
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Virtual circuits; e.g., using multiprotocol encapsulation via RFC1490 over frame relay or RFC 1483 over ATM.
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Various VPN mechanisms over the Internet; e.g., using IPSec or Layer 2 transport protocol (L2TP).
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Circuit-switched connections (e.g., analog modems, ISDN).
It doesn’t stop there. Routers also support protocols that allow aggregation of serial links for more scalable bandwidth, via mechanisms such multilink PPP (over leased lines), multilink frame relay, and ATM Inverse Muxing. These mechanisms provide added resiliency, and speeded recovery when individual links fail. Routers also provide WAN resiliency features. At medium and larger sites, multiple physical paths (in extreme cases over physically diverse access configurations, even from multiple carriers) are configured with dynamic routing provided by the router. At smaller sites, routers manage an on-demand backup via analog modems and ISDN. Routers also perform WAN data compression to use WAN links more efficiently. Using the Internet for site-to-site connectivity introduces yet more requirements in the area of IP VPN tunneling support on the one hand, and firewalls on the other.
SIMPLIFICATION COMING TO A NETWORK NEAR YOU
It’s becoming a single protocol IP world. The industry direction is towards IP for everything, so the complexity of multiprotocol routing networking is decreasing dramatically. The reasons are numerous: IP is ubiquitous in enterprise networks and the Internet, more people understand IP than any other protocol, gateways for non-IP applications exist, and protocol stacks are readily available at both the IP and higher levels (e.g., TCP).
It’s becoming a LAN technology Ethernet world. Ethernet has matured to become the LAN technology of choice with the best price/performance, with robust 100-plus Gbps switching platforms and with link speeds heading to 10 Gbps. There are compelling reasons to not only use Ethernet in new sites but to move to Ethernet as quickly as possible in existing sites.
It’s becoming a simpler WAN world with emerging Ethernet MAN/WAN connectivity, combining the flexibility and price performance of Ethernet with the reliability and scalability of optical systems. WAN encapsulation (everything runs on Ethernet), WAN data compression (optics delivers scalable bandwidth), and configuring IP tunneling and firewalls (Virtual Private Ethernets are as secure as frame relay) are no longer relevant in an Ethernet WAN environment. The result is WAN interfaces that are just like campus links including support of Ethernet-based link aggregation (through mechanisms such as split MultiLink
Trunking).
So a simplifier, faster, and more reliable enterprise networking world is emerging with the convergence onto Ethernet and IP. The key elements of this new world are QoS-enabled Ethernet switches in the wiring closets, IP and Ethernet-optimized routing switches in the campus cores, and private or managed Optical Ethernets across the MAN and WAN.
STRATEGIC IMPERATIVES FOR ENTERPRISES
IT networking managers are on a treadmill of continuous upgrades, configuration and management complexity, and steep learning curves associated with today’s enterprise networks. But there is a better way!
Enterprises need to establish end-to-end Optical Ethernet in the LAN/MAN/WAN as their strategic direction. In this model, routing functionality is delivered through IP and Ethernet-optimized routing switches at the core of a logically extended metropolitan campus network with smaller metro sites being logical wiring closets within this network. The value proposition includes a substantial improvement in the total cost of ownership of enterprise networks, data distribution, and application processing, opening up new opportunities for outsourcing and freeing up budgets for strategic investments in e-business initiatives such multi-channel customer care and supply chain management. In the transition period, legacy routers serve as multiprotocol gateways encapsulating all traffic onto IP, non-Ethernet LAN gateways, and as legacy WAN gateways to virtual and physical circuit networks.
Having established their direction, enterprises need to complete their evolution towards an Ethernet-only switched LAN and IP-only routed environments. Many enterprises (particularly in the high-tech, utility, and education segments) have done this, leveraging intelligent Layer 2 switches in the wiring closets and routing switches in the campus backbones.
At the same time, they need to leverage the installed base of fiber optics access to medium and large sites through private and managed Optical Ethernets — first in the MAN and then across the WAN between major metro sites. Most sites today that have multiple T1 connections are already likely served by fiber.
Finally, they need to push service providers for broader deployment of Optical Ethernets to other metro sites. This is a realizable opportunity. Communications Industry Researchers (CIR) estimates that 100,000 business sites in the United States are already connected via fiber, while CIBC World Markets estimates that 76 percent of small and medium-sized business sites are within one mile of fiber. Most major municipalities are proactively working towards establishing optical infrastructures in their communities as an important enabler of economic development. At the same time, many utilities are starting to realize the economic values of their rights of way to every building in their serving areas.
Routing in an IP and Ethernet world can provide much higher price/performance, can be simpler to configure and manage, and can be more reliable through integration with optics. This in turn can open up new opportunities right across IT by allowing rethinking of application and storage deployment and significantly improving IT user and application performance. Tony Rybczynski is director of strategic
marketing and technologies for Nortel Networks’ Enterprise
solutions unit. E-mail questions or comments to tonyryb@nortelnetworks.com.
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