White Paper: Knowing your boundaries

In this white paper, 3Com outlines the needs that prompted the development of the Boundary Routing System and how it can help...

In this white paper, 3Com outlines the needs that prompted the development of the Boundary Routing System and how it can help your organisation

More effective use of WAN services

The following powerful routing enhancements are supported by Boundary Routing, and also:

Data compression, which allows lower-speed lines to carry more traffic, significantly reducing WAN costs

Class of Service, implementing data prioritisation to speed the processing of key applications

Custom filtering to provide network security and traffic control

Switched line support, including support for Frame Relay, ISDN, dialled lines, and X.25, enabling cost savings in remote office WAN connections

Implementation of smart filters, reducing traffic and lowering costs across the WAN

Disaster recovery capability, which provides dial backup when the router detects a primary line failure

Sophisticated network management based on agent recognition of entire systems

Reduced equipment costs

Boundary Routing drives down equipment costs by centralising most router operations so that a few full-function routers in main offices can provide services for many lower-cost routers at the network periphery. International Data Corporation (IDC), a leading marketing research firm, estimates that approximately two million LANs worldwide are not yet internetworked by any form of WAN connection. Around 40 per cent of these LANs are projected to be interconnected in the next three to four years.

There are many compelling reasons to expand and interconnect existing LANs into a WAN. In combination, these reasons intensify the pressures to enhance both information-based business services to increase competitiveness and reliable communications to strengthen business relationships. In Europe it is estimated that around 35 per cent of all new WAN connections are used for links between companies-suppliers, customers and industry partners. An organisation that neglects LAN interconnections can find itself at a competitive disadvantage.

The costs and complexity of remote office internetworking

Organisations typically justify the costs of network infrastructure by its critical business benefits in terms of improved information availability and distribution. However, many organisations have reached a level of network growth at which further expansion is blocked by a phenomenon that could be termed a "complexity crisis". This crisis occurs when the complexity of managing, monitoring and ensuring the uptime of the network grows faster than the network itself. This is illustrated by comparing network size against its complexity, which directly relates to the cost of adding new remote sites.

At a certain point, the complexity of adding new remote sites increases exponentially, resulting in a leap in administrative cost and a corresponding decrease in reliability. Once this point has been reached, the benefits of bringing remote sites into the network infrastructure are outweighed by the costs.

Administrative costs

A key reason for the importance of remote site cost control is the expense of management staff. Contrasted with WAN transmission and capital expenses ( which decline over time due to wider availability of a mix of services (such as ISDN, Switched 56, Frame Relay and other on-demand services) and reduced hardware prices ( the expense of the extra staff needed to install and maintain small remote offices becomes an ever-increasing part of the cost equation.

The increases in staff costs for remote site management go far beyond customary increases for personnel. Managing remote sites can take extraordinarily large amounts of time. Industry studies have shown that although the minority of network users (as few as 10 per cent) are based remotely, these users can consume up to 90 per cent of network administration time. This time is costly. The skill sets to effectively administer a WAN are broad, including skills in telecommunications, network protocol operations, and LAN media. Trained administrators may be difficult and expensive to find. Yet many organisations, because of economic considerations, have had to reduce their administrative staff, with resulting pressure to increase staff productivity.

WAN management costs also involve the opportunity costs of lost productivity if an administrator is unable to cope with the ever-increasing workload of expanding and maintaining a large network. Cumulatively, this suite of cost-related problems can have a devastating effect on an organisation's ability to meet its business objectives ( ultimately leading to its inability to cover or exploit a particular market and seriously inhibiting the organisation's growth. The solution requires WAN links that are highly efficient to administer, with minimal installation, configuration and maintenance tasks. At remote sites, the ideal solution eliminates configuration altogether, letting the local router learn the configuration automatically from the central site router to which it is connected. Otherwise, remote site management will be complex, time-consuming and expensive.

WAN service costs

Telecommunications charges for the lines between offices are a significant component of WAN costs. Rates and services vary widely by geographic area. These recurring costs often dominate the overall cost of network ownership. In the past, most interoffice connections have been leased lines ranging from 9.6Kbit/s to T1/E1 speeds (1.54Mbit/s / 2.0Mbit/s). Monthly access charges for these lines can be as high as several thousand pounds per site.

In many cases, using on-demand switched media such as Frame Relay, X.25, ISDN and dialled connections can contribute significantly to cost savings. This is because switched media costs are based on actual WAN utilisation across multiple organisations, as opposed to the fixed costs of bandwidth permanently allocated to one organisation. Techniques such as data compression, traffic prioritisation and custom filtering also contribute significantly by allowing more efficient use of existing leased lines and other types of connection.

Equipment costs

Equipment costs, also referred to as capital or acquisition costs, usually make up a relatively small part of total WAN expenses, but in many cases they are a focal point because they are easier to identify and negotiate with a supplier.

Total costs for the equipment may seem minor if an organisation plans to link a few remote sites, but when the organisation starts thinking in terms of connecting several hundred remote sales offices, the cost of the equipment becomes a very significant factor. If remote users require the same full routing capabilities as centrally located users, the cost can escalate rapidly; the organisation cannot employ low-cost remote site routers when they offer a very limited subset of the protocols and other features that users need. Analysis of equipment costs should recognise that the expense of a central site router can be justified by related cost savings in remote site routers ( provided those routers meet user requirements. The analysis can warrant the cost of a central site router that offers more ports, protocols, and fault tolerance in WAN links and power supplies.

Boundary Routing takes standard routing software for n-way local routing and extends the LAN interface portion of that software over the WAN. This results in a set of new, greatly simplified routing software functions for the remote router.

In other words, Boundary Routing addresses the issue of routing by viewing the central and remote site devices as a single system. This innovation provides all the benefits of configuring a single interface, much like the central device in a collapsed backbone LAN environment, but in a large WAN network. Because there is little need for configuration of the central or remote router WAN ports, management complexity is reduced. The software innovations of Boundary Routing add a new level of simplicity and economy to the hardware advantages associated with access routers, but without limiting the remote sites' choice of routing protocols.

Complete routing functionality

Routing functions are essential in a large network. In a purely bridged network, broadcasts and multicasts are propagated around the network and may cause flooding of the WAN links. Remote offices connected via bridging receive all of the broadcast traffic from the whole network. The remote offices themselves issue relatively few broadcasts and multicasts when compared to the rest of the network. On the other hand, in a purely routed network, routing table updates and other routing protocol traffic can significantly increase the level of utilisation of the WAN link. With Boundary Routing, this traffic is not needed by the remote router; the central router holds the tables that define the rest of the network topology. Boundary Routing therefore provides an effective firewall between the remote office and the rest of the network. Equally important, Boundary Routing preserves the remote offices' ability to take advantage of facilities such as Class of Service data prioritisation, custom filters and data compression. Boundary Routing supports these facilities without compromising the level of access and the routing capabilities available to remote users. Initially, these facilities may be configured manually. As implementation continues and more facilities are added, configuration will become automated.

Reducing complexity at remote offices

Boundary Routing puts technological complexity where it can be handled ( at the central site ( and shifts it away from the remote locations. The following example illustrates Boundary Routing in action, indicating the types of decisions made by the central and peripheral routers. In this example, several large sites have WAN connections to small remote sales offices in order to check order status interactively.

How Boundary Routing solves the problems of cost and complexity for remote offices

3Com's Boundary Routing represents a fundamental rethinking of WAN architecture. Boundary Routing simplifies router administration at remote sites by transferring complexity to a central location, where administrative expertise is usually located. Router installation at the remote sites becomes a quick, three-step process. Configuration changes, software upgrades and other administrative tasks for the remote site routers become centralised, allowing a few administrators to manage multiple sites quickly and efficiently. By shifting complexity from the peripheral router to a central router, Boundary Routing greatly reduces the cost of installing and managing remote office connections.

Reducing administrative costs

At a central location, Boundary Routing can reduce the time it takes to connect many remote sites because configuration needs to be performed only on the central router. Central router installation requires only one additional command for each port performing Boundary Routing. Without the need to configure remote routers, the time required for making complex network changes, such as the addition of a new protocol, is also minimised.

Streamlining address management

Boundary Routing also simplifies addressing schemes within a network. Traditionally, each WAN link has been implemented as a subnetwork separate from the central or remote office LAN. Separate WAN subnets generate a huge need for address space ( and address space, especially for TCP/IP, is at an absolute premium. Boundary Routing solves this problem by using the same administrative domain (or subnetwork) for the remote LAN and the WAN, thus reducing address space by as much as 30 per cent, and also reducing the size and complexity of the routing tables. This in turn reduces the amount of routing table update traffic being exchanged between routers.

Reducing WAN service costs

Boundary Routing reduces equipment costs by using the full routing capabilities of the central site router; at the remote site, this allows a low price point for hardware and no extra cost for software. For example, the fact that the central router handles most routing tasks eliminates the need for routing protocols at the remote office, reducing memory requirements for the remote site router.

Additional Boundary Routing features

The following Boundary Routing features add significantly to its effectiveness in addressing a wide range of requirements for remote office internetworking.

( Switched Line Support and Auto-configuration

Boundary Routing supports Frame Relay, dialled lines (PSTN and ISDN), and X.25, enabling remote offices to use switched media. Using the capabilities of Boundary Routing to detect the type of interface to which the remote router is connected (for instance, a modem, Frame Relay switch, or leased line), the router attempts upon initial power on to connect to a central site. When this initial attempt is successful and the central router is available, communications begin and the router is fully operational. However, if the central router is unavailable, the remote router waits until the central router initiates communication. The remote router then responds, downloads any configuration information needed, and immediately becomes fully operational.

( Smart filters

Smart filters reduce the traffic across the WAN and prevent unnecessary use of switched media. To understand how they do this, it is necessary to understand the nature of the information that is exchanged between two routing devices.

A significant percentage of the information sent across a WAN link is not user data, but information employed by routers to maintain network integrity. As a network grows, the amount of traffic needed to maintain the network increases. For instance, in a Novell environment, every server issues Service Advertisement Protocol messages on a regular basis to advertise the services that are available at the servers. The servers also take part in routing information packets that are sent on a regular basis. This information is essential; without it, end-stations or clients cannot access services on the network. But using smart filters at the central router can significantly reduce this type of traffic across the WAN. These smart filters block unnecessary traffic to the remote site router, producing significant cost savings. In addition, the remote site router replies locally to the server at the remote site and exchanges only opportunistic updates with the central router.

( Management enhancements

Boundary Routing devices support full SNMP manageability. Upon installation, the remote router learns its address from the central router, and the remote device has its own individual agent. Most network management platforms today see each device and in some cases each module or even port as an individual entity in a network. As network management becomes more sophisticated and as agent development becomes recognised as an area of much higher priority, management platforms will see systems rather than individual devices, modules, and ports. Boundary Routing contributes to this advance in network management. The remote device is already an integrated part of the Boundary Routing system, which may be viewed as one network entity.

The benefits of Boundary Routing

Boundary Routing provides an innovative and extremely effective method of adding smaller remote offices to a network. By minimising the costs and complexity of remote site router administration, equipment, and WAN links, the architecture addresses many of the major issues confronting network planners, implementers, and administrators today.

As remote sites grow and network topologies change, network professionals may need to convert a site from Boundary Routing to conventional routing. 3Com makes the transition easy by offering software upgrade kits to quickly change a remote router running Boundary Routing software to a conventional router operating in a meshed topology and supporting X.25, Frame Relay, ISDN, SMDS, or other WAN services.

( Bandwidth-on-demand

Bandwidth-on-demand supplements an existing communications link (for instance, a 56Kbit/s or 64Kbit/s leased line with an on-demand extra line). The extra line is dialled automatically once a traffic threshold is reached, and then disconnected once a configurable time has elapsed after the traffic level falls back below the capacity of the primary line.

( Disaster recovery

Disaster recovery capability automatically dials a back-up connection when a router detects that the primary line has gone down, allowing quick recovery of a potentially disastrous break in communication.

( Scheduler

A scheduler is based on sophisticated macro capabilities that set up a timetable to automatically dial a line and carry out other specific tasks. This facility can limit WAN line costs to a predictable ceiling by preventing a line from being up all the time. This facility is implemented at the central site router, allowing central manipulation of the dialled line.

( Data compression

Data compression contributes greatly to the efficiency of WAN communications. It lowers WAN costs by removing repetitive patterns of data from packets before transmission over the LAN, and restoring them on the receiving end. Because less data is sent, the capability allows lower-speed, point-to-point (leased or dialled) lines to be used much more effectively. In some cases, WAN lines can carry as much as four times the amount of traffic as they could without data compression.

( Class of service prioritisation

Class of Service (CoS) gives the capability to decide which types of traffic have a higher priority for transmission across the WAN link. 3Com supports CoS for all routed protocols as well as bridging. By specifying a mask and an interleave factor, it is possible to decide the priority of an IP Telnet or NetBEUI or IPX connection over the other traffic to be sent.

( Dial-on-demand

Dial-on-demand lets a device dial the WAN link only when a packet needs to be sent. Routing protocols have traditionally been designed to send a packet across an available tested link. Therefore 3Com's implementation allows protocols to assume that a WAN link is available. The service decides when a packet needs to be sent, dials the connection, and takes the connection down after a certain time. This implementation is done on a protocol-by-protocol basis.

Compiled by Mike Burkitt

(c) 1998 3Com Corporation

Read more on Voice networking and VoIP