Backhaul 101

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Backhaul 101

Introduction to the proposed regulated backhaul
services

December 3rd 2007
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Content

• What is Backhaul?
• Generic Concepts
• Access Seekers Nearest Available Point of
  Interconnection (NAPOI)
• Isolated NAPOIs and Virtual Designated Point of
  interconnection (VDPOIs)
• Elected Points of Interconnection (EPOIs)
• Regulated UCLL backhaul
• Regulated UBA backhaul
• The role of commercial backhaul
• Glossary
• Questions
• Appendix A Information on UBS/Basic UBA
• Appendix B Aggregation

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What is Backhaul?

• A formal definition of "backhaul" is "the
  process of transmitting information to a central
  point from which it can be distributed over a
  network".
• Backhaul services usually carry traffic on a
  "point-to-point" basis, without making complex
  switching decisions about where to send the
  traffic.
• Backhaul allows Access Seekers to connect
  customers in places where they do not own their
  own networks.

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What is Backhaul?

• The backhaul service connects an exchange-based
  tail or service to another handover point.
• A handover point is the boundary between one
  service and another, or between a service and a
  Handover Link.
• A Handover Link is a cable that connects the
  Handover Point to the Service Provider equipment
  (which may be co-located or at a different site)
• Regulated backhaul will be ethernet only.

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Why is it necessary?

• To understand the role of backhaul, consider a
  phone call. It starts at one telephone, travels
  to an exchange, travels on a trunk to another
  exchange, and ends at another telephone. Since
  it's expensive to run millions of wires between
  telephone exchanges, the telecommunications
  industry has developed a host of technologies
  which allow one transmission system to carry many
  calls (known as trunking). The telephone
  exchange becomes a collection point, which
  aggregates tens, hundreds, or thousands of calls
  onto a single transmission link between
  exchanges.The same need exists for data
  networks like the Internet. Customer traffic is
  aggregated close to the users, so that the
  transmission system can carry a large number of
  requests on a small number of links.If an
  Access Seeker doesn't own a trunk network then it
  needs to find some way of moving around traffic
  from a large number of customers. An ISP may have
  all its switches in Auckland, with subscribers
  all over New Zealand. To connect a customer in
  Greymouth the ISP needs to pay another
  telecommunications carrier to collect the
  customer traffic in Greymouth, carry it to
  Auckland, and deliver it to the ISP's data
  centre. This is an example of a backhaul service.

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What is bandwidth?

• In telecommunications, "bandwidth" measures how
  much information a network can carry. And because
  most modern telecommunications services are based
  on digital networks, digital measures of
  bandwidth have become the most common and most
  familiar way to express the capacity of all kinds
  of network links.Bandwidth is expressed in
  multiples of bits per second. A standard
  telephone is allocated 64 Kbps (kilobits, or
  thousands of bits) per second of communications
  bandwidth. Backhaul networks, which carry the
  traffic of huge numbers of customers, are
  measured in millions of bits per second (megabits
  per second, or Mbps), up to billions of bits per
  second (gigabits per second, or Gbps).

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Generic concepts - NAPOI

• Access Seekers Nearest Available Point of
  Interconnection.
• The NAPOI are defined as 29 geographic points
  around New Zealand that have been chosen to
  optimise network efficiency. Currently 16 of
  these sites are operational and 13 additional
  sites are still awaiting EAS deployment.
• 16 have already been deployed Auckland Central,
  Glenfield, Henderson, Mt Albert, Torbay, Remuera,
  Papakura, Papatoetoe, Hamilton, Wellington,
  Naenae, Porirua, Christchurch, Riccarton,
  Dunedin, Howick
• 13 are to be built Cromwell, Greymouth,
  Invercargill, Kerikeri, Levin, Napier, Nelson,
  New Plymouth ,Palmerston North, Rotorua,
  Tauranga, Timaru, Whangarei
• These points were discussed and agreed at the
  TCF.

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Generic concepts iNAPOI and VDPOI

• For Access Seekers with UCLL or EUBA in the new
  NAPOI areas, where no competitive infrastructure
  exists within 5 kilometres of the relevant NAPOI,
  eg Kerikeri or Cromwell (known as an isolated
  NAPOI or iNAPOI), then a virtual designated point
  of interconnect (VDPOI) will be assigned, if
  requested. For example, Dunedin may be the VDPOI
  for the Cromwell NAPOI.
• The network investment manager determines the
  VDPOI for each iNAPOI. The VDPOI is the
  geographically closest NAPOI to the iNAPOI. The
  network investment manager will inform product
  management to manage the transition from iNAPOI
  to NAPOI.

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Generic concepts EPOI (UCLL only)
An Access Seeker may also elect to terminate the
UCLL Backhaul service at an intermediate point
between the First Handover Point and the NAPOI.
These points, for the purposes of this document,
are defined as an Access Seekers elected point
of interconnection (EPOI) and their use as an
EPOI is subject to the following rules
The EPOI must be one of Telecoms UBA First Data
Switch sites that the UCLL Backhaul Service
transits between the First Handover Point and the
NAPOI Once the EPOI is established, the UCLL
Backhaul Service from all local telephone
exchanges served by that EPOI will terminate at
that point instead of the NAPOI and The UCLL
Backhaul Service is not available from the EPOI
to any NAPOI An example would be in Queenstown
where the Access Seeker may have presence in that
location despite it not being a NAPOI
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Regulated UCLL Backhaul

• UCLL/Co-location allow Access Seekers to install
  their own access equipment which connects to
  Telecoms copper loop.
• This equipment can be in the Telecom Exchange
  (co-located) or external.
• The equipment connects to the handover point
  using a Handover Link.
• Regulated backhaul will connect the site to the
  NAPOI (or VDPOI/EPOI).The Access Seeker can
  aggregate their own UCLL traffic onto a single
  regulated backhaul.
• Commercially they will be able to aggregate
  non-UCLL traffic.

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Demarcation Regulated UCLL Backhaul

• The Access Seeker installs their DSLAM in the
  local exchange.
• They connect to the UCLL Handover Point using a
  Handover Link.
• Regulated backhaul goes from a relevant frame in
  an exchange to the relevant frame at the NAPOI
  (or VDPOI/EPOI)
• NAPOIs are defined as 29 Tier 0,1 and 2 sites.
• The Access Seeker must either
• (a) handover at the UCLL HoP
• (b) handover at the NAPOI, VDPOI, or EPOI or
• (c) use commercial backhaul to take them to
  another agreed POI.

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Regulated EUBA backhaul

• EUBA services on an EAS can be aggregated across
  a common backhaul infrastructure to the NAPOI (or
  VDPOI).
• Each Access Seeker would specify how much
  bandwidth they required.
• The Access Seeker can effectively specify a
  contention ratio.
• The traffic priority tagging will specify how
  traffic is managed.
• It is the responsibility of the Access Seeker to
  ensure applications are managed end to end to
  ensure this capacity is not flooded.
• EUBA traffic from several EAS can be aggregated
  at the NAPOI on to a single Handover Link,
  subject to bandwidth. Note that this aggregation
  could also be contended.

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Demarcation Regulated EUBA Backhaul

• The Enhanced UBA tail includes both the ADSL2
  line and the connectivity between the DSLAM and
  the Ethernet Aggregation Switch.
• Regulated backhaul goes from the trunk side of
  the EAS to the NAPOI etc.
• NAPOIs are defined as 29 Tier 0,1 and 2 sites.
• The Access Seeker must either
• (a) handover at the EAS HoP
• (b) handover at the NAPOI or VDPOI or
• (c) use commercial backhaul to take them to
  another agreed POI.

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Handover Links and connections

• The Handover Link connects Access Seeker
  equipment to the physical Handover Point, or OFDF
  at the NAPOI etc.
• The handover connection is used to connect the
  trunk side of the EAS to the Handover Point and
  is only required for EUBA tails
• A Handover Link is required to connect the
  Access Seeker equipment to the backhaul service,
  irrespective of whether that is commercial or
  regulated backhaul.
• UCLL will have a handover link in the unbundled
  exchange as well as the NAPOI

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Commercial Backhaul

• Why is it important?
• Commercial backhaul will link the 29 NAPOI with
  one another allowing Access Seekers to transport
  across metro areas and nationally.
• What is the market need?
• There are a different options available
  dependant on the Access Seekers requirements.
  Some Access Seekers will need national point to
  point links and other will want multi-product
  (regulated and commercial products), multipoint
  backhaul services.
• Who will provide commercial services?
• There is currently a number of different
  providers offering a range of commercial backhaul
  service.

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Additional Questions

• Telecom infers that each local exchange (for UCLL
  Backhaul) or first data switch (FDS) (for UBA
  Backhaul) is assigned to a particular NAPOI. Can
  Telecom please provide a list of which local
  exchange or FDS it proposes should be assigned to
  each NAPOI.
• Link
• Telecom interprets the NAPOI as being that which
  is nearest to the End User. Will this potentially
  require the Access Seeker to either extend their
  network to each NAPOI nominated by Telecom or
  purchase backhaul commercially? Could this also
  require the Access Seeker to interconnect with
  multiple NAPOIs in the same centre (i.e.
  Auckland, Wellington and Christchurch) in order
  to get backhaul traffic from local exchanges in
  more than one NAPOI area.
• Yes.  Multiple NAPOIs in the larger cities
  reflect the structure of Telecoms NGN.  Telecom
  itself connects at each of these NAPOIs on an
  equivalence basis so Access Seekers face no
  competitive disadvantage from this structure. 
  The need for multiple NAPOIs is to provide
  diversity and load balancing. Eg There is a
  maximum number of customers supported by each
  NAPOI.

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Additional Questions

• Telecom has reserved the right to designate new
  NAPOIs, and perhaps withdraw existing NAPOIs,
  from time to time. Under what circumstances would
  this re-designation occur?
• The NAPOIs align with the Tier 0,1 and 2 nodes
  in our network architecture.  The location of
  these nodes is driven by the population density
  i.e. we limit the maximum number of end customers
  served by a single node, and network transport
  links design and reliability issues primarily
  driven by geographic factors e.g. if an area is
  geographically isolated we may put more equipment
  in the region for service reliability reasons. 
  Changes will be driven by things like population
  changes e.g. if the population in a region grows
  sufficiently we may need to create a new Tier 2
  node, and we might conceivably remove a Tier 2
  node if sufficient diverse links became available
  to a geographically isolated area.
• For UBA Backhaul, the FDSs and the NAPOIs are
  co-located (except for the Upper Hutt FDS). As
  Telecom interprets the NAPOI as being that which
  is nearest to the End User, would there be any
  need for UBA Backhaul apart from the Upper Hutt
  FDS?
• In the future yes the number of FDS will
  expand as the Telecom network is deployed.
• See link

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Additional Questions

• Why has Telecom chosen NAPOI locations which are
  different to the existing POIs for UBS, Basic UBA
  and voice interconnection? Can Telecom please
  provide a list of the POI locations for UBS,
  Basic UBA and voice interconnection.
• The NGN is a fundamentally different and new
  network compared to the PSTN.  Therefore there is
  no particular reason why PSTN POIs should map to
  NGN NAPOIs.  UBS and BUBA are ATM services, the
  NAPOIs are Ethernet-related services.  So again
  there is a different network with different
  nodes. However overtime as Telecom moves from
  PSTN to VOIP based services and migrates from ATM
  to Ethernet these points will be consolidated.
• POI list
• Can Telecom please describe the purpose of the
  NAPOI variants, namely VDPOI, iNAPOI and EPOI.
• Covered in earlier slides
• EPOIs only exist for UCLL Backhaul and must be at
  one of Telecom's UBA FDSs. However, the FDSs and
  the NAPOIs are co-located (except for the Upper
  Hutt FDS), so what purpose do the EPOIs currently
  serve?
• None currently but as with question 4 the need
  will become more apparent has the new network is
  deployed.

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Additional Questions

• When no Access Seeker or third party has existing
  network infrastructure capable of offering a
  backhaul service for the UCLL/UBA Service within
  5 kilometres of a particular NAPOI and has no
  plans to build such infrastructure, then the
  geographically closest NAPOI will be defined as a
  VDPOI. Can Telecom please explain how it was
  determined that 5km was the appropriate distance?
• The VDPOI definition relates to national
  backhaul rather than the regulated regional
  backhaul this is an important distinction to
  bear in mind as the competition tests are
  different.  For national backhaul the issue is
  whether there is a national backbone connection
  sufficiently close to the NAPOI to enable a
  reasonable connection so that it is possible to
  compete in the market for connecting NAPOIs
  together in relation to each NAPOI.  For
  regulated backhaul the issue is whether there is
  a fibre network in the area able to be used to
  provide the exchange to NAPOI (UCLL) or FDS to
  NAPOI (UBA) connection.  The 5 km is an
  historical number which was used in relation to
  how far from a POI an interconnect link would be
  run for the standard charge.  Beyond the 5 km an
  additional charge was made for the extra costs
  Telecom would be incurring by providing long
  distance interconnect links.  It had seemed that
  this was a reasonable proxy for extending out
  from a NAPOI.

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Additional Questions

• Can Telecom please explain how the indicative
  list of exchange groupings in Appendix 5 of the
  STPs is intended to be used?
• This list is to help Access Seekers map
  exchanges/FDS to NAPOIs.
• Why has Telecom proposed two speed options for
  UCLL Backhaul and four speed options for UBA
  Backhaul? Why arent the four speed options
  available for both backhaul options? Can Telecom
  please explain how the speeds were determined?
• Unlike UBA backhaul, UCLL backhaul does not pass
  through any aggregation device therefore the
  speeds can only be constrained by the Network
  Interface Device (eg media converters) and there
  is only a limited bandwidth available on these
  devices.
• Speed steps were determined through consultation
  with the TCF which took into consideration the
  minimum number of customers required for UCLL and
  EUBA.
• Why has Telecom proposed a point to point service
  for UCLL Backhaul and an aggregated service for
  UBA Backhaul?
• EUBA passes through an Ethernet aggregation
  switch therefore makes EUBA aggregation
  possible . UCLL backhaul doesn't pass through
  an aggregation switch therefore it cannot easily
  aggregate the UCLL services, however, Access
  Seekers can insert their own aggregation devices.

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Additional Questions

• Why has Telecom proposed 20 distance steps for
  the monthly rental price, when there are five
  steps (S plus A to D) for the Telecom commercial
  backhaul product?
• The cost of backhaul is a function of distance,
  geography, capacity and technology. When drafting
  the STP we were aware that some incumbents
  overseas have adopted a fixed cost plus a per
  metre/km cost approach. Whilst this is the
  closest approximation to underlying cost, the
  advice we received was that it would have been
  impractical from a billing perspective.
  Accordingly, we selected as small a number of
  distance groupings as possible that would be a
  fairly accurate proxy of underlying cost but be
  able to be implemented from a billing
  perspective. Plus the number of groupings did
  result in a fair spread across all the potential
  backhaul permutations. Greater granularity in
  price will more optimally enable the pricing
  structure of the service to more accurately
  reflect the underlying cost structure of this
  service. As such, the greater the number of price
  points, the more efficient signals pricing will
  provide to Access Seekers leading to more optimal
  allocations of resources.
• Whilst the Commission has noted that our
  commercial backhaul product has 5 bands, we do
  not consider this relevant as the pricing is not
  cost plus but value maximising. Whilst cost is an
  important factor when setting pricing under a
  value maximising construct, there are other
  factors to consider including capacity,
  competition and business objectives. This
  service is more analogous to the UPC service
  which the Commission benchmarked with 11 cost
  steps.

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Additional Questions

• Why has Telecom not proposed a price for the 100
  Mbps capacity handover connection?
• It was an error.
• Which parties took part in the TCF working party
  on the backhaul services?
• Kenneth Barnett (CallPlus)
• Sebastien Pham (ihug/Vodafone)
• Craig Young (TelstraClear)
• Mike Moran (Telecom)
• Chris Dyhrberg (Telecom)
• Alan Mitford-Taylor (Telecom)
• Jeremy Hall (Telecom)
• Steven Bond-Smith (Orcon)
• Gary Hooker (Telecom Retail) 
• Paul Clarkin (WorldxChange) 
• Tex Edwards (NZ Comms) (occasional attendance)

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Glossary

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Glossary
Slide 24
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Questions?
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Appendix A UBS/Basic UBA

• UBS/Basic UBA is sold as an L2TP tail from the
  end-user premises to the first ATM Data Switch
  (USAP)
• However the interface specification requires we
  insert an L2TP Access Concentrator (LAC) into the
  tail. This is done by routing traffic through a
  BRAS and into the IP Core.
• We then route the L2TP tunnel to the designated
  USAP or Point of Interconnect.
• Regulated Backhaul, which is between the first
  Data Switch and the NAPOIs, is not needed because
  the basic tail, with zero backhaul, already is at
  the USAP/NAPOI.

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Appendix A UBS comparing how we sell with what
we build

• The above diagram shows how we sell the
  service, i.e. Tail commercial backhaul, versus
  how we build the service.
• Technically the tail includes the LAC, which is
  delivered on the same BRAS used by Xtra Retail,
  the IP Core and the ATM Node.
• The requirement for a LAC means that the traffic
  is routed to the actual handover ATM node
  directly
• This could create an anomaly where the designated
  USAP is actually closer to the LAC than the URSA
  USAP. However we bill based on where the user is,
  not where the BRAS is.
• Any backhaul dimensioning is solely done over the
  ATM-ATM POI link
• Ethernet Backhaul is currently being trialed.
  This can be done easily because the interface is
  L2TP over IP the IP layer hides the Layer 2
  (Ethernet or ATM) technology.

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Appendix A UBS/Basic UBA URSAs and USAP

• Unbundled Regional Service Areas
• The country is divided into geographical areas.
  All DSLAMs in those areas belong to that URSA
  (see picture).
• Unbundled Service Aggregation Point
• Each URSA has a USAP which correlates to the
  first data switch.This is the first point
  interconnect can occur for UBS Customers.Sometime
  s the USAP is not in the URSA, for example
  Northlands USAP is located at Airedale st
  Exchange.Mayoral Drive has four USAPs (four
  different ATM switches) to cover North Auckland,
  North Shore, Hobsonville and West Auckland URSAs.
  The ISP either uses four handover links at
  Mayoral drive or pays commercial backhaul to
  combine them into one handover link.
• Point of Interconnect
• This is where the service is handed over to the
  Service Provider. It must be a USAP.Some
  customers have multiple POIs.
• Regulated Backhaul
• All UBS POIs coincide with NAPOIs and as such no
  regulated options exist.
• Commercial Backhaul
• Commercial backhaul is the logical distance
  between the first USAP and the actual POI.
• As the tail ends within the IP Core, the
  physical and logical backhaul constructs are
  different.

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Appendix B What is Aggregation?

• Having one physical backhaul circuit per tail is
  uneconomic. To make it economic it is necessary
  to aggregate multiple services onto the same
  backhaul service.
• Aggregation allows multiple services to share a
  common bandwidth, which is often less than the
  sum of the services. The ratio of non-aggregated
  bandwidth to aggregated bandwidth is known as the
  contention ratio.
• Aggregation requires an aggregation function at
  each end. There are several options
• The Service Provider can aggregate their services
  in their equipment at both ends.
• Telecom can aggregate traffic at both ends, or at
  just one end.
• EAS-based services are aggregated by default and
  therefore it makes sense to deliver as an
  aggregated service.
• UCLL is easier to deliver as point-to-point
  ethernet, with aggregation as an additional item.

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Appendix B Multi-service Aggregation Issues
Aggregation Functions Sharing Bandwidth
Aggregation allows us to combine service
instances together Contention Contention allows
us to aggregate several services together over a
smaller bandwidth than the sum. VLAN mapping To
ensure uniqueness it may be necessary to
translate VLAN addresses to new ones.Parameter
Mapping It is possible to map other parameters
such as Priority settings, if required.

• Aggregating several services means that you
  require a pipe that can carry all of those
  services simultaneously.
• The services need to be compatible with each
  other, e.g. not use overlapping VLAN IDs.VLAN
  IDs are particularly an issue as these need to be
  unique in the new pipe
• Other ethernet characteristics need to be at
  least compatible and ideally constrained
  equally.
• The backhaul or handover (both points of
  aggregation) can be smaller than the sum of
  bandwidths of the inputs, but if so then the
  behaviour of what happens when the pipe is
  congested needs to be defined and managed at the
  point where the contention occurs. Again this
  could constrain some features.
• For EAS-based services the EAS can act as an
  aggregator, so services could be aggregated on to
  the single backhaul service.
• For UCLL the traffic would need to pass through
  an aggregator device, which does not currently
  exist.

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