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IP Office Product Description

IP Office 4.2

Page 161

Issue 18.b.- (08 July 2008)

7. Data Networking Services

LAN/WAN Services

Computers connected to an IP network in an office communicate via the LAN (Local Area Network). To support

small networks both Small Office Edition and IP406 incorporate a Layer 2 Ethernet switch. The Small Office

Edition supports 4 ports (with a fifth Ethernet port as a firewalled Layer 3 switch), the IP406 supports 8 ports.

The IP412 and IP500 support a firewalled 2 port Layer 3 Ethernet Switch only.

When computers on the LAN communicate they do not care where the destination is, they just send messages

with the address of the destination. These messages are likely to be received at all other computers on the

same network but only one – the target destination – will act on the message. Where the destination is on

another network, the router is needed to be the "gateway" to the rest of the world and find the optimum route

to send the message on to the destination. The router alleviates the need to establish and hold a call for the

duration of a communication session (when messages or IP packets are being sent between source and

destination) by automatically establishing a connection only when data is to be passed. Routers may be

connected together using WAN (Wide Area Network) links that could be point-to-point leased lines, managed

IP networks, Frame Relay networks or exchange lines (Central Office). The IP Office system supports all of

these types of network connections.

IP400 systems have a Wide Area Network (WAN) port that can be connected to a digital leased line service

using either X.21 or V.35 interface at speeds up to 2048kbps. Point-to-Point protocol (PPP) is used over this

link. The data within the call uses the Point-to-Point Protocol (PPP) which is used by the vast majority of

manufacturers for linking routers. PPP support is essential if it is not the same manufacturer's equipment at

each end of the link. Addition WAN ports can be added using up to two WAN3 10/100 external expansion

modules. On Small Office Edition systems a single option WAN port card can be added. IP500 systems do not

support this type of port.

Exchange lines (Central Office) can also be used in the event of failure of the WAN link or to provide alternate

or top up bandwidth on demand.

All IP Office systems have an integral router with support for bandwidth on demand that allows the negotiation

of extra bandwidth dynamically over time. Where connection is over ISDN, IP Office initiates extra data

connections between sites only when there is data to be sent or sufficient data to warrant additional channels.

It then drops the extra channels when they are no longer needed. The calls are made automatically, without

the users being aware of when calls begin or end. The rules for making calls, how long to keep calls up etc, are

configurable within IP Office.

It is possible to have several different routing destinations or paths active at any time linking the office to

other offices and the Internet simultaneously.

Quality of Service

IP Office supports 802.1p packet prioritization. 802.1p is a specification for giving Layer 2 switches the ability

to prioritize traffic (and perform dynamic multicast filtering). The prioritization specification works at the media

access control (MAC) framing layer of the OSI model. To be compliant with 802.1p, Layer 2 switches must be

capable of grouping incoming LAN packets into separate traffic classes. Eight classes are defined by 802.1p.

Although network managers must determine actual mappings, IEEE has made broad recommendations. The

highest priority is seven, which might go to network-critical traffic such as Routing Information Protocol and

Open Shortest Path First table updates. Values five and six might be for delay-sensitive applications such as

interactive video and voice. Data classes four through one range from controlled-load applications such as

streaming multimedia and business-critical traffic - carrying SAP data, for instance - down to "loss eligible"

traffic. The zero value is used as a best-effort default, invoked automatically when no other value has been

set. In operation, 802.1p calls for the use of priority fields within the packet to signal the switch of the priority-

handling requirements.

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