TELECOM ACCESS STANDARDS NEWSLETTER NO. 140 June 2003 CONTENTS 1. TELECOM'S NEXT GENERATION NETWORK 2. RESIDENTIAL-TYPE PREMISES WIRING DEVELOPMENTS 3. ETHERNET ADSL MODEMS RECOMMENDED 4. PTC 200 AMENDMENT: "DECADIC ONLY" DIALLING NO LONGER ACCEPTED 5. USE OF AUSTRALIAN TEST REPORTS 6. V.92 MODEM SUPPORT 7. USING "CALL WAITING" DURING AN INTERNET SESSION 8. TELEPERMITTING PRINCIPLES RETURN TO MAIN INDEX 1. TELECOM'S NEXT GENERATION NETWORK It is now fairly common knowledge in the telecommunications industry that Telecom has entered into a long-term agreement with Alcatel, which will be the primary supplier of equipment for Telecom's Next Generation Network (NGN). There is also an agreement with BCL, under which we will be able to better serve some remote rural customers. Work is currently progressing on the detailed specification of our new network equipment, with the aim of replicating the present TNA 102/PTC 200 analogue interfaces to the maximum possible extent. Nevertheless, there will be some changes, as modern telecommunications practices no longer support some of our earlier services. Newsletter No. 117, in December 1999, covered the main changes that were expected, but it is worth repeating the key points that were published at that time:- 1. New network transmission equipment installed in our access network since 1981 has not supported "Bothway analogue 2-wire DDI service". As a result, we are not able to support new installations of this service. As a reminder, PABX suppliers should mark their copies of PTC 107, clause 6.13.2, that this service has not been available for new connections since 1996; 2. New network transmission equipment installed in our access network since 1988 provides reduced line current to shorter lines than does the NEAX exchange line interface. Typically, no more than about 25 mA is provided, even on short lines. We still design the access network to supply at least 20 mA to the line and its CPE, but this reduced current has already impacted on the practicability having two or more CPE items "off-hook" at the same time. In particular, it affects V.92 "Modem on Hold" capability (more on this in item 6); 3. Some access systems may deliver a lower open circuit ringing voltage. However, this will not have any impact on the ringing requirements of PTC 200; 4. Ringing cadence distortion may occur in some cases, due to the need to repeat the exchange ringing via additional interfaces within the access network. However, this will be kept within current tolerances indicated in PTC 200; 5. Ringing detection via an earth reference is not expected to be supported, so it should be confirmed that all CPE will detect loop ringing (wire to wire) reliably; 6. Line polarity reversals when the line is seized for an incoming call from the network may or may not occur according to the type of access system used. Also, polarity changes may or may not take place with each ringing burst. As for point 5 above, CPE must detect ringing on incoming calls; Background information on these changes is given in Newsletter No. 117, which is also available from our website. We will advise via these Newsletters if any other changes in the analogue network interface are expected. 7. Confirming advice given many times over the past several years - new network equipment will not support decadic dialling CPE (see item 4 for more details). 2. RESIDENTIAL-TYPE PREMISES WIRING DEVELOPMENTS The NGN is expected to bring a wide range of new services for Telecom customers, well beyond the current Plain Old Telephone Services" or "POTS. Some of these services are in the final planning stages, while others have hardly yet been thought about in any real detail. Nevertheless, the broadband and multi-media capabilities of the NGN mean that our customers will have a lot to look forward to in the future. We have been considering how best residential-type premises wiring practices can be evolved to support these new services. International cabling standards are being developed to cover "Home Electronic Systems" and related matters, covering complete systems that will support building management, security, entertainment distribution, etc, etc. These systems are essentially developments of commercial building cabling systems and SOHO systems already connected to the Telecom network. On the other hand, they tend to be much more complex than most residential customers either need, or are willing to pay for. SOHO While SOHO has been available for some years (PTC 225 was published in 1998), there has been limited take-up of these systems, largely due to their higher cost, and partly due to customers having little perception of any current need for the flexibility offered by these systems. PTC 103 and PTC 225 already cover the use of SOHO cabling systems, which provide full flexibility between services or lines and specific jackpoints. As such, suppliers can be confident that such systems will be suitable for most future applications. However, we have been looking into systems that would be more suitable for the average customer, who probably does not yet see any need for these new services and is unwilling to pay the much higher installation costs of SOHO. Our current residential-type wiring Code of Practice, PTC 103, deals primarily with low cost, high reliability, "loop" or "daisy chain" wiring from jackpoint to jackpoint, using 2-pair cable and our standard "2-wire" jackpoints. This is fine for POTS but, when new non-POTS services are made available, it is expected that one or more specific jackpoints will need to be allocated to those services. Disadvantages of "loop" wiring Unfortunately the present "loop" wiring does not readily provide for separating out individual jackpoints to use them for specific functions, such as access to a second line, access to JetStream, or to any other of the future multiple services. Second lines are a good example in that one or more new cables may have to be run from the network termination to new jackpoints. In some cases, the second pair of a 2-pair cable can be used, along with a dual outlet jackpoint, but this cable also needs access to the network termination, either directly or via a nearby jackpoint. Purpose-designed grease-filled connectors are usually necessary for this work, but neither these connectors nor their specialised tools are usually held the average customer. Where "daisy-chained" wiring is used for JetStream, each POTS jackpoint must be fitted with an ADSL line filter. These cost around $20 each and some can look quite unsightly for home use. Line filters cannot be used if an alarm system has been installed "behind" a jackpoint or there are more than 5 "POTS" jackpoints. In such cases, a Telecom-installed line splitter is currently needed, along with a new "dedicated" JetStream jackpoint at which the ADSL modem will be connected. However, this loses the flexibility of allocating any jackpoint for ADSL, as provided by the line filters. Security and medical alarm installation companies and other parties installing devices that need immediate "line break-in" to override any existing calls during emergencies often face difficulties in getting their cables to existing jackpoints. As a result, there is a tendency to take short-cuts by connecting their cable into the middle of an existing cable run. This is frowned on by Telecom, as such joints may be prone to failure. Also, they are sometimes made in locations which are not readily apparent to repair staff, who may then have to face the expense of running a new cable to restore service. Recommendations In reviewing our residential cabling practices, our objective has been to make some recommendations for the "ordinary customer" building a new home and not wanting to spend too much at this stage. It also applies to the small business customer, many of whom will be using residential-type wiring, as distinct from the structured cabling used by larger companies. "Star wiring" is a clear winner on most counts. Star wiring involves a separate cable from each jackpoint to a central panel on which those cables terminate. By having separate cables, any jackpoint can be dedicated to a specific service, as and when the need arises. We have been working with some cabling hardware suppliers to develop some simple, low cost, termination hardware for a "star wiring" solution. In its simplest form, the panel houses a line and service/line termination strip and a commoning strip for the jackpoints connected on each POTS line. We expect the first supplies of such hardware to be available early in August. This hardware is intended primarily for those customers building a new home, although it could also be used by those re-wiring existing premises. Obviously, the best time to install cabling in a new home is after the framing is completed but before any lining is fitted. Cable is relatively cheap in "per metre" terms and, although star wiring uses more cable, it does not add much cost to a new installation. Another interesting point is that 4-pair Cat 5 cable, as used in commercial buildings, is not much more expensive than our standard 2-pair cable - sometimes, it can be cheaper! We are now recommending that 4-pair Cat 5 cable be used in all new installations. Most network services can be supported on 2-pair cable, but providing four pairs is something of an "insurance policy" in that it provides added flexibility for future services, some of which may require all four pairs to be used. Even though we recommend that 4 pair cables are installed, we still recommend the standard "2-wire" jackpoint for most residential customers because virtually all CPE is fitted with the matching 6-way BT plug. Other types of jackpoints may be needed for special services in the future, but most of those installed are likely to continue to support POTS services and the 2-wire type obviously does this. Where a different jackpoint is needed, the 2-wire type is easily changed, as long as plenty of spare cable is left at both ends of the run. An example of "new" services (although they are not new to business customers or to "technically oriented" home customers) is the distribution of a Telecom network-based service, such as "JetStream", around the home via an Ethernet Home LAN. With star wiring, specific jackpoints can be diverted from the commoned POTS line termination to one supporting an ADSL modem/router, but only if the cable is already in place in the walls and there is sufficient spare cable left for diverting it at the star point. This suggests that customers planning a new home need to think about more than just current POTS services when they are deciding on their jackpoint provisioning. Once suitable star point hardware is available on the local market, more on this subject will be published in a future Newsletter. Meantime, PTC 103 (Code of Practice for Residential-type Premises Wiring) and PTC 225 (Requirements for SOHO cabling installations) are being revised and these will be published on our website in due course. 3. ETHERNET ADSL MODEMS RECOMMENDED Many of Telecom's new network services will be delivered by one or other varieties of xDSL, the most common of which is ADSL. "JetStream" is already well-established as the high speed internet service delivered by ADSL. However, there is also SHDSL, which is a symmetrical version and capable of carrying up to 2 Mbit's in both upstream and downstream directions. This is slower on short lines, but more rugged than ADSL on long lines. As such, it is expected to be adapted for rural residential applications in the future. JetStream is now available to over 83% of the New Zealand population and there are already over 100 different types of ADSL modem now holding Telepermits. These vary from quite low cost "budget" PCI (internal modems) and USB modems through to relatively high cost external modem/router integrated units. One really good development from the customer's viewpoint is that all of these have reduced substantially in price since JetStream service was introduced here in 2000. Within the home, any distribution of these non-POTS services is expected to be via Ethernet, so a modem with an Ethernet port and PPPoE capability will be an advantage for later use, even if it is not essential today. As with all purchases, the customer has to make a choice on which one to buy. The low cost ones certainly meet today's requirements for a single PC, but PC's notoriously seem to need up-grading (in reality, usually replacing) every 3 - 4 years. As a result, more and more homes already have, or soon will have, two or more PC's. Rather than throw out the old one, it can be networked with the new one at relatively low cost. With a 10/100 Mbit/s Ethernet card at around $20 for each PC, they can be connected together via a cross-over Ethernet cable. More of a network can be set up with a low cost Ethernet hub, but two or more PC's can access JetStream if the customer purchases an ADSL modem/router. While a PCI or USB modem is cheaper, it does not offer this "future" capability. There is also the problem that many PCI and USB modems tend to be a bit "underpowered" on marginal lines. Should our "Check your line for JetStream" facility (see (http://www.telecom.co.nz/tools/1,3907,100551-201803,00.html ) indicate that only marginal performance can be expected, a potential purchaser should ask the retailer to advise whether a particular product is likely to be satisfactory. It would be worth ensuring that the product can be exchanged if it proves unsuitable for the line concerned. Telecom's future broadband-based services will be multi-media capable, such that high speed data, music and video can supplement, or even replace POTS, as the carrier of voice, security alarm, fax and dial-up modem services. These new services can be "integrated" with a home network if an Ethernet modem/router supporting PPPoE is used. These modems would be the most "future adaptable" types currently available. It is recommended that customers purchase one of these, rather than a lower cost PCI or USB modem, as long as they have the extra cash available. Needless to say, an Ethernet modem fits in well with the star-wiring recommended in item 2 above. For suppliers and retailers, the above points might be a useful argument to "up-sell" customers who show an interest in purchasing an ADSL modem. 4. PTC 200 AMENDMENT: "DECADIC ONLY" DIALLING NO LONGER ACCEPTED As was last mentioned in Newsletter No. 139, our "traditional" reverse decadic signalling is one feature that will certainly NOT be supported by the Next Generation Network interface. In fact, Telecom and its suppliers have recognised that decadic signalling is now "past its time" and we do not expect our future network equipment to support either "reverse" or "normal" decadic signalling. As a formal "matter of record", PTC 200 is being amended to delete the existing clause 5.4 in its entirety and replace it with the formal notification that our reverse decadic signalling CPE is no longer acceptable for Telepermit purposes. TNA 102 will remain unchanged at this stage, as it accurately describes the decadic signalling characteristics of the existing network. This change will have virtually no impact on the CPE market, as no decadic-only signalling equipment has been Telepermitted for many years. Way back in 1988, Access Standards advised that Telecom's network was essentially wholly DTMF-capable and we subsequently recommended that no suppliers bother to face the cost of "reversing" the decadic dialling of overseas products. Since that time, virtually all CPE has used standard DTMF signalling, although some have also offered a "normal decadic" option. Now that we now know that new network equipment will not be supporting decadic signalling, it would be quite unfair for a customer to purchase such equipment, only to find that it no longer works when we upgrade the network. In the unlikely event that there is still any "decadic signalling only" CPE being offered for sale, it is recommended that this be withdrawn. Overseas-sourced CPE, which still provides for both DTMF and "normal" decadic signalling, is still acceptable for Telepermit purposes provided that either the decadic signalling option is disabled, or that its default setting is DTMF and there are clear warnings in the user manual that the product is NOT to be set to decadic when used on the Telecom network. 5. USE OF AUSTRALIAN TEST REPORTS We continue to receive requests that we accept test reports prepared in Australia to the ACA's TS- or S-series technical standards. While we appreciate that Telepermit applicants do not wish to pay for testing to be duplicated unnecessarily, the Australian analogue networks do have some different characteristics to those of the Telecom network. As a result, at least some supplementary testing to PTC 200 may be necessary. Because of overhead charges and the need to sort out just what has to be done, this work can cost almost as much as a full test. The other difficulty for us is that the test sequences used in Australian specifications are quite different, so we have to spend a lot more time assessing the level of compliance. This reflects in our additional charges for processing Telepermit applications based on overseas test reports. Depending on product complexity, it might be easier to have full PTC 200 testing carried out than rely on the acceptability of Australian test reports. Needless to say, though, Australian test reports are acceptable to Telecom for electrical safety (AS/NZS/IEC 60950 is common to both countries) and AS/NZS 3548 is acceptable to the Ministry of Economic Development for EMC. 6. V.92 MODEM SUPPORT It appears that making the features offered by V.92 modems work properly have been something of a puzzle for the modem industry so far. Newsletter No. 131, December 2001, outlined the problems we saw in designing a sequence for picking up and releasing an incoming call. To prepare for their introduction, Newsletter No. 132 was published in February 2002. This invited industry comment on some provisional PTC 200 requirements for Telepermitting this class of modem. Subsequent investigations have revealed that the operational issues are even more significant than we had expected. As a result, the provisional PTC 200 requirements of Newsletter No. 132, Appendix No. 1 are now withdrawn. We see claims on the internet that "the killer application for V.92 operation is that the internet user no longer needs to miss an incoming call when he/she is on-line". As a result, expectation of a workable Modem on Hold (MoH) feature could be a major factor in any decision to "up-grade" a V.90 modem or buy a new V.92 modem. Telecom has been assessing some samples of V.92 modems connected to a Network Access Server (NAS) set up with V.92 support software. So far, we have not found any that can work properly because they all "double terminate" the line by leaving the modem connected in parallel with the telephone used to pick up an incoming call. Reliable operation is dependent on the dc characteristics of both the modem and any telephone connected with it. Modems usually have a lower dc voltage across them relative to a typical telephone and the telephone can be made inoperable if the modem "hogs" too much of the line current. Because of the double termination, even if they do work, telephones will usually suffer bad sidetone. Most of our customers attempting to use MoH will be affected to at least some extent, as well as degrading the transmission performance perceived by anyone who calls them while they are "on-line", but operating the MoH feature. Our testing shows that the modem user usually loses the transmit capability of his telephone well before he loses the receive capability. Because of this, it may not be realised that the incoming caller is unable to hear. There have been other problems too, but MoH has been one particularly serious issue that has stalled the industry's wide support for V.92 operation for some time now, despite the fact that the ITU Recommendation has been published since 2000. We will be revising other Telepermit requirements for this class of modem - hopefully in the near future. However, at this stage it is clear that "double terminations" are not acceptable for reliable operation, other than for fleeting durations during switching from modem to telephone and back. If and when everything is finalised, it is expected that those V.92 modems offering correctly operating Modem on Hold will be granted Telepermits in a new PTC 218-series. This will help customers, retailers and our own faults staff to differentiate between "upgraded" PTC 211-series V.90 modems or "claimed" V.92 modems of unknown capability, and those V.92 modems that have been proven to work under all line conditions. As a side issue, any upgrading of in-service V.90 modems by a customer does strictly cancel that modem's original Telepermit. This is particularly the case where such "upgrading" causes service problems. 7. USING "CALL WAITING" DURING AN INTERNET SESSION While there is concern about Modem on Hold, it is possible that many modems and other specialised devices will recognise our Call Waiting Tone, as long as the user has not included the tone disabling code prefix "*52" before the number dialled to reach the ISP. If a modem or other device can recognise the tone and provide an alert to the user, whether "on screen" or via some other means, the user can click on "work off-line" and drop the modem call. The network will then ring back, allowing the user to pick up the phone and speak to the caller. This option obviously drops the internet session, but it provides an acceptable means of "not missing a call while you are on-line", without the risk of degraded telephone performance. A number of adjunct devices are already available that work in a similar way. One caution though, is that Telecom does not provide Caller Display with the Call Waiting tones. As a result, it is not possible to see who is calling before the internet session is dropped. 8. TELEPERMITTING PRINCIPLES There has been some confusion recently over what classes of CPE need to be granted Telepermit for connection to the Telecom network. This may have been due to the Australian system, which allows some classes of product to be connected to a network if the ACA has not defined network connection requirements. The position with respect to the Telecom network is quite different. Essentially, our logic is that it is pointless to define detailed requirements for connection of equipment if there is not a specific network service requiring that class of equipment. This lack of specifications does not mean that suppliers can connect such equipment to other network services which might happen to support it. Telecom provides defined services, not the means for other parties to connect "anything" to circuits which have been leased for other purposes. Section 106 of the Telecommunications Act 2001 states, in rather formal legal terms, " ....a person may only connect equipment to a network, or to anything connected to a network, that is owned or operated by an operator who has agreed to the connection." In plainer language; Telecom's agreement is required before any product may be connected to its network. This agreement is represented by the granting of a Telepermit. Some classes of equipment have been specifically excluded from Telepermit requirements by Telecom. These include commercial building cabling and related hardware components; and devices (such as PC's) connected behind Telepermitted modems or Telecom-provided Network Terminating Units (provided these limit signal levels transmitted directly or indirectly into our analogue network). Even then, there are exceptions to the latter category. These include any devices which determine analogue speech levels, even though they may connect behind Telepermitted or Telecom-supplied interface equipment. If in doubt about the Telepermit requirements for any product, please contact Access Standards for a ruling - don't assume it can be connected if there is apparently no relevant PTC specification. DOUG BURRUS Manager Access Standards