LOCAL NUMBER PORTABILITY ADMINISTRATION WORKING GROUP (LNPA WG)
INTERPRETATION OF N-1 CARRIER ARCHITECTURE

[NOTE: The yellow highlighting throughout this document is meant to
provide focus on text from the various cites and industry documentation
that is directly relevant to the specific LNPA interpretation it
addresses.]{.mark}

NOTE: Throughout the discussions in the LNPA WG of the N-1 LNP
Architecture and the responsibilities of carriers in ensuring calls are
routed properly to the called party, carriers expressed concerns over
the network impacts and costs to perform LNP queries on default routed
calls. The LNPA WG would like to stress that if all carriers complied
with the following interpretation of the N-1 architecture, based on
research of FCC mandates, and performed the necessary LNP query when
they were designated as the N-1 carrier on a call to a portable NXX
code, a carrier rarely would be forced to perform the query on a
default-routed basis.

**FCC NOTICE OF APPARENT LIABILITY FOR FORFEITURE, DA 04-1304, RELEASED
MAY 13, 2004, ¶¶ 5 (Quoted from the Notice):**

**5.** Furthermore, in adopting, with some modification, recommendations
of the North American Numbering Council ("NANC") as set forth in a
\[LNPA\] Working Group Report, the Commission clearly imposed
requirements on the carrier immediately preceding the terminating
carrier, designated the "N-1 carrier," to ensure that number portability
databases are queried and thus that calls are properly routed.
Currently, call routing is accomplished by use of Location Routing
Numbers ("LRNs"). Under the LRN method, a unique ten-digit number is
assigned to each central office switch. The routing information for end
users who have ported their telephone numbers to another carrier is
stored in a database, with the LRNs of the switches that serve the
ported subscribers. Carriers routing calls to customers with ported
numbers query this database to obtain the LRN that corresponds to the
dialed number. This query is performed for all calls to switches from
which at least one number has been ported. In adopting the \[LNPA\]
Working Group Report, the Commission noted that if the N-1 carrier does
not perform the database query, but instead relies on another entity to
perform the query, the other entity may charge the N-1 carrier in
accordance with long-term number portability cost allocation and
recovery guidelines.

-   LOCAL CALL:

> INTERPRETATION:

-   The originating carrier is the N-1 carrier and is responsible for
    performing the query in its network or entering into an agreement
    with another entity to perform the queries on its behalf.

CITE:

-   **Third Report and Order, FCC 98-82, ¶¶ 15-16, (1998) (Quoted from
    the Order):**

**15.** For a carrier to route an interswitch telephone call to a
location where number portability is available, the carrier must
determine the LRN for the switch that serves the terminating telephone
number of the call. Once number portability is available for an NXX,
carriers must \"query\" all interswitch calls to that NXX to determine
whether the terminating customer has ported the telephone number.
Carriers will accomplish this by sending a signal over the SS7 network
to retrieve from an SCP or STP the LRN associated with the called
telephone number. [The industry has proposed, and the Commission has
endorsed, an \"N minus one\" (N-1) querying protocol. Under this
protocol, the N-1 carrier will be responsible for the query, \"where
\'N\' is the entity terminating the call to the end user, or a network
provider contracted by the entity to provide tandem access.\" Thus the
N-1 carrier (*i.e.* the last carrier before the terminating carrier) for
a local call will usually be the calling customer\'s local service
provider]{.mark}; the N-1 carrier for an interexchange call will usually
be the calling customer\'s interexchange carrier (IXC). [An N-1 carrier
may perform its own querying, or it may arrange for other carriers or
third parties to provide querying services on its behalf.]{.mark}

> **16.** To route a local call under this system, the originating local
> service provider will examine the seven-digit number that its customer
> dialed, for example \"456-7890.\" If the called telephone number is on
> the originating switch (*i.e.* an intraswitch call), the originating
> local service provider will simply complete the call. If the call is
> interswitch, the originating local service provider will compare the
> NXX, \"456,\" with its table of NXXs for which number portability is
> available. If \"456\" is not such an NXX, the

originating local service provider will treat the call the same as it
did before the existence of long-term number portability. If it is an
NXX for which portability is available, the originating local service
provider will add the NPA, for instance \"123,\" to the dialed number
and query \"(123) 456-7890\" to an SCP containing the LRNs downloaded
from the relevant regional database. The SCP will return the LRN for
\"(123) 456-7890\" (which would be \"(123) 456-XXXX\" if the customer
has not changed carriers, or something like \"(123) 789-XXXX\" if the
customer has changed carriers), and use the LRN to route the call to the
appropriate switch with an SS7 message indicating that it has performed
the query. The terminating carrier will then complete the call. To route
an interexchange call, the originating local service provider will hand
the call off to the IXC and the IXC will undertake the same procedure.

-   **FCC Consent Decree Order, DA 04-2065, Released July 12, 2004, ¶¶
    9(d):**

**9(d).** Upon execution of this Consent Decree, company-wide on all 398
of its host switches and whenever (Carrier X - name deleted) is the N-1
carrier, (Carrier X - name deleted) will perform or will have performed
on its behalf, a database query to obtain the Location Routing Number
("LRN") that corresponds to any dialed number. Whenever it is the N-1
carrier, (Carrier X - name deleted) will ensure that any call placed by
a (Carrier X -- name deleted) customer to a ported telephone number is
properly routed to the network of the current carrier serving that
telephone number, based on the LRN.

-   TOLL CALL:

> INTERPRETATION:

-   For an interLATA Toll call, the IXC is the N-1 carrier and is
    responsible for performing the query in its network or entering into
    an agreement with another entity to perform the queries on its
    behalf.

> CITE:

-   **Third Report and Order, FCC 98-82, ¶¶ 15-16, (1998) (Quoted from
    the Order):**

**15.** For a carrier to route an interswitch telephone call to a
location where number portability is available, the carrier must
determine the LRN for the switch that serves the terminating telephone
number of the call. Once number portability is available for an NXX,
carriers must \"query\" all interswitch calls to that NXX to determine
whether the terminating customer has ported the telephone number.
Carriers will accomplish this by sending a signal over the SS7 network
to retrieve from an SCP or STP the LRN associated with the called
telephone number. The industry has proposed, and the Commission has
endorsed, an \"N minus one\" (N-1) querying protocol. Under this
protocol, the N-1 carrier will be responsible for the query, \"where
\'N\' is the entity terminating the call to the end user, or a network
provider contracted by the entity to provide tandem access.\" Thus the
N-1 carrier (*i.e.* the last carrier before the terminating carrier) for
a local call will usually be the calling customer\'s local service
provider; [the N-1 carrier for an interexchange call will usually be the
calling customer\'s interexchange carrier (IXC). An N-1 carrier may
perform its own querying, or it may arrange for other carriers or third
parties to provide querying services on its behalf.]{.mark}

> **16.** To route a local call under this system, the originating local
> service provider will examine the seven-digit number that its customer
> dialed, for example \"456-7890.\" If the called telephone number is on
> the originating switch (*i.e.* an intraswitch call), the originating
> local service provider will simply complete the call. If the call is
> interswitch, the originating local service provider will compare the
> NXX, \"456,\" with its table of NXXs for which number portability is
> available. If \"456\" is not such an NXX, the
>
> originating local service provider will treat the call the same as it
> did before the existence of long-term number portability. If it is an
> NXX for which portability is available, the originating local service
> provider will add the NPA, for instance \"123,\" to the dialed number
> and query \"(123) 456-7890\" to an SCP containing the LRNs downloaded
> from the relevant regional database. The SCP will return the LRN for
> \"(123) 456-7890\" (which would be \"(123) 456-XXXX\" if the customer
> has not changed carriers, or something like \"(123) 789-XXXX\" if the
> customer has changed carriers), and use the LRN to route the call to
> the appropriate switch with an SS7 message indicating that it has
> performed the query. The terminating carrier will then complete the
> call. [To route an interexchange call, the originating local service
> provider will hand the call off to the IXC and the IXC will undertake
> the same procedure.]{.mark}

INTERPRETATION:

-   For an intraLATA Toll call where the originating carrier is the
    Pre-subscribed IntraLATA Carrier for the calling party, the
    originating carrier is the N-1 carrier and is responsible for
    performing the query in its network or entering into an agreement
    with another entity to perform the queries on its behalf.

> CITE:

-   **Technical Requirement T1.TRQ.2-2001, Technical Requirement on
    Number Portability Switching Systems, Prepared by T1S1.6 (quoted
    directly):**

> **\<REQ-00500\>**
>
> **An NP Query shall only be sent when:**

-   **an NP trigger has been encountered, and**

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-   **the FCI indicates "number not translated".**

> **However, the query will not be performed if,**

-   **the called number is served by this switch and the transition
    mechanism (as specified in \<REQ-08600\>) does not apply to the
    called number, or**

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-   **the call is identifiable as destined for an operator, or**

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-   **[the call is to an interexchange carrier, as indicated by
    presubscription or dialed digits (101XXXX) (for exceptions see
    \<CR-00950\>).]{.mark}**

> **\<REQ-00900\>**
>
> **[If an NP trigger is encountered and IXC routing (not LEC routing)
> is assured prior to launching the NP query, the NP query shall be
> bypassed, and the call routed to the predialed carrier, or
> presubscribed carrier (PIC)]{.mark}, or group carrier, or lastly to
> the Office provisioned interLATA carrier (for exceptions see
> CR-00950).**
>
> **\<CR-00950\>**
>
> **If an NP trigger is encountered and IXC routing (not LEC routing) is
> assured prior to launching the NP query, the switch shall launch the
> NP query if the call is to be routed to any of the specific designated
> set of IXCs provisioned by \<CR-08550\>. This specification shall be
> on a per route basis for each of the designated carriers. The switch
> shall not perform the NP query for calls to be routed to any other
> IXC.**
>
> **The default behavior shall be as described in REQ-00900.**
>
> **This requirement shall not apply to operator-destined calls.**
>
> **When the NP query is performed, the call shall be routed to the
> predetermined carrier and route.**
>
> [The originating LEC shall perform the NP query on behalf of an IXC
> only when business arrangements are in place that explicitly allow the
> LEC to perform the NP query.]{.mark}
>
> Some tandem switches can not perform this capability.

-   Based on current end office switch functionality, if the originating
    switch has the 6-digit LNP trigger set on an intraLATA Toll NXX
    code, and the originating carrier is the intraLATA Toll PIC for the
    calling party, the originating switch will launch a query to the LNP
    database and route the call based on the response from the database.
    Based on this established switch functionality, the LNPA WG believes
    the originating carrier is the N-1 carrier in this call scenario.

> INTERPRETATION:

-   For an intraLATA Toll call where the originating carrier is NOT the
    Pre-subscribed IntraLATA Carrier for the calling party, the
    Pre-subscribed IntraLATA Carrier is the N-1 carrier and is
    responsible for performing the query in its network or entering into
    an agreement with another entity to perform the queries on its
    behalf.

> CITE:

-   **Refer to cites above from Technical Requirement T1.TRQ.2-2001,
    Technical Requirement on Number Portability Switching Systems,
    Prepared by T1S1.6**

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-   Based on current end office switch functionality, if the originating
    switch has the 6-digit LNP trigger set on an intraLATA Toll NXX
    code, and the originating carrier is NOT the intraLATA Toll PIC for
    the calling party, the originating switch will NOT launch a query to
    the LNP database and will route the call unqueried to the calling
    party's intraLATA Toll PIC. Based on this established switch
    functionality, the LNPA WG believes the calling party's intraLATA
    Toll PIC is the N-1 carrier in this call scenario, similar to the
    IXC scenario.

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-   DEFAULT QUERIES (A.K.A. QUERY OF LAST RESORT OR DONOR SWITCH
    QUERIES)

> **PLEASE REFER TO NOTE AT THE BEGINNING OF THIS DOCUMENT.**
>
> INTERPRETATION:

-   If an LNP query is not performed previously in the call path, the
    call will continue to route on the dialed digits until it could
    eventually reach the LERG-assigned switch for the dialed NPA-NXX.
    This will put that LERG-assignee in the position of performing a
    default LNP query if the dialed digits are within a portable
    NPA-NXX.

> CITE:

-   **Third Report and Order, FCC 98-82, ¶¶ 21, (1998) (Quoted from the
    Order):**

> **21.** In the *Second Report and Order*, the Commission determined
> that if an N-1 carrier arranges with another entity to perform queries
> on the carrier\'s behalf, that other entity may charge the N-1 carrier
> in accordance with requirements to be established in this *Third
> Report and Order*. [The]{.mark}
>
> [Commission also noted that when an N-1 carrier fails to ensure that a
> call is queried, the call might inadvertently be routed by default to
> the LEC that originally served the telephone number. If the number was
> ported, the LEC incurs costs in redirecting the call. This could
> happen, for example, if there is a technical failure in the N-1
> carrier\'s ability to query, or if the N-1 carrier fails to ensure
> that its calls are queried, either through its own query capability or
> through an arrangement with another carrier or third-party. The
> Commission determined in the *Second Report and Order* that if a LEC
> performs queries on default-routed calls, the LEC may charge the N-1
> carrier in accordance with requirements to be established in this
> *Third Report and Order*.]{.mark} The Commission determined further
> that it would \"allow LECs to block default-routed calls, but only in
> specific circumstances when failure to do so is likely to impair
> network reliability.\" The Commission also said that it would
> \"require LECs to apply this blocking standard to calls from all
> carriers on a nondiscriminatory basis.\"

INTERPRETATION:

-   A carrier may bill the N-1 carrier for performing the default query
    when the N-1 carrier default routes a call unqueried.

> CITE:

-   **First Memorandum Opinion and Order, FCC 97-74, ¶¶ 125-126 (1997)
    (Quoted from the Order):**

> **125.** Discussion. We deny Pacific\'s request that we require all
> N-1 carriers, including interexchange carriers, to meet the
> implementation schedule we established for LECs. Such a requirement is
> not mandated by the 1996 Act, which subjects only LECs, not
> interexchange carriers engaged in the provision of interexchange
> service, to our number portability requirements. Moreover, petitioners
> have not demonstrated a need for us to impose such requirements under
> our independent rulemaking authority under Sections 1, 2, and 4(i) of
> the Communications Act of 1934, as amended. In that regard, we are not
> convinced that Pacific\'s hypothetical situation, whereby the N-1
> carrier would not perform any queries and the original terminating LEC
> would thus have to perform all the queries not performed by the
> originating LEC, will arise often. The industry already appears to
> favor using the N-1 scenario, under which the N-1 carrier performs the
> database query, as indicated in the majority of comments on call
> processing scenario issues received pursuant to the original Notice of
> Proposed Rulemaking. The vast majority of interLATA calls are routed
> through the major interexchange carriers, and the two largest
> interexchange carriers, at least, claim they plan to deploy
> portability as soon as possible. Therefore, most interLATA calls will
> be queried by the major interexchange carriers, not the incumbent
> LECs. Moreover, as we stated in the First Report & Order, we wish to
> allow carriers the flexibility to choose and negotiate among
> themselves which carrier shall perform the database query, according
> to what best suits their individual networks and business plans.
> Finally, we decline to address Pacific\'s argument that, if the
> terminating carrier is forced to perform queries, that would violate
> our fourth performance criterion. Since we are eliminating our fourth
> performance criterion, Pacific\'s argument is moot.
>
> [**126.** We clarify, however, per NYNEX\'s request, that if an N-1
> carrier is designated to perform the query, and that N-1 carrier
> requires the original terminating LEC to perform the query, then the
> LEC may charge the N-1 carrier for performing the query, pursuant to
> guidelines the Commission will establish in the order addressing
> long-term number portability cost allocation and recovery.]{.mark}

-   **Second Report and Order, FCC 97-289, ¶¶72-75 (1997) (Quoted from
    the Order):**

> **72.** The *Architecture Task Force Report* considered and made
> recommendations on several issues which were not otherwise addressed
> in the *Technical & Operational Task Force Report*, including the
> following: (1) what entity shall be required to make the query to
> determine the service provider of the called party (N-1 Call Routing);
> and (2) whether carriers may block default routed calls (Default
> Routing). Because these two specific issues will have a significant
> impact on the efficiency and effectiveness of local number
> portability, each will be discussed more fully below.

**73.** [N-1 Call Routing.]{.underline} The NANC recommends that the
carrier in the call routing process immediately preceding the
terminating carrier, designated the \"N-1\" carrier, be responsible for
ensuring that database queries are performed. None of the parties
commenting on the NANC\'s recommendations addresses this issue. We adopt
the NANC\'s recommendation that the N-1 carrier be responsible for
ensuring that databases are queried, as necessary, to effectuate number
portability. The N-1 carrier can meet this obligation by either querying
the number portability database itself or by arranging with another
entity to perform database queries on behalf of the N-1 carrier.

> **74.** In the *First Order on Reconsideration*, the Commission
> recognized that queries would most likely be performed by the N-1
> carrier if the industry adopted the Location Routing Number solution.
> Industry consensus is that the Location Routing Number system is the
> best method to satisfy the Commission\'s performance criteria for
> long-term local number portability. The efficient provisioning of
> number portability requires that all carriers know who bears
> responsibility for performing queries, so that calls are not dropped
> because the carrier is uncertain who should perform the database
> query, and so that carriers can design their networks accordingly or
> arrange to have database queries performed by another entity.
> Consistent with our finding in the *First Order on Reconsideration*,
> we conclude that the Location Routing Number system functions best if
> the N-1 carrier bears responsibility for ensuring that the call
> routing query is performed. Under the Location Routing Number system,
> requiring call-terminating carriers to perform all queries may impose
> too great a burden on terminating LECs. In addition, obligating
> incumbent LECs to perform all call routing queries could impair
> network reliability.
>
> **75.** We note, however, that the requirement that the N-1 carrier be
> responsible for ensuring completion of the database query applies only
> in the context of Location Routing Number as the long-term number
> portability solution. In the event that Location Routing Number is
> supplanted by another method of providing long-term number
> portability, we may modify the call routing process as necessary. [We
> note further that if the N-1 carrier does not perform the query, but
> rather relies on some other entity to perform the query, that other
> entity may charge the N-1 carrier, in accordance with guidelines the
> Commission will establish to govern long-term number portability cost
> allocation and recovery.]{.mark}

INTERPRETATION:

-   Unless specified in business arrangements, carriers may block
    default routed calls incoming to their network in order to protect
    against overload, congestion, or failure propagation that are caused
    by the defaulted calls. (This is a direct quote from the
    Architecture Plan.)

> CITE:

-   **Second Report and Order, FCC 97-289, ¶¶76-78 (1997) (Quoted from
    Order):**

> **76.** [Default Routing.]{.underline} [The NANC recommends that we
> permit carriers to block \"default routed calls\" coming into their
> networks.]{.mark} A \"default routed call\" situation would occur in a
> Location Routing Number system as follows: when a call is made to a
> telephone number in an exchange with any ported numbers, the N-1
> carrier (or its contracted entity) queries a local Service Management
> System database to determine if the called number has been ported. If
> the N-1 carrier fails to perform the query, the call is routed, *by
> default*, to the LEC that originally serviced the telephone number.
> The original LEC, which may or may not still be serving the called
> number, can either query the local Service Management System and
> complete the call, or \"block\" the call, sending a message back to
> the caller that the call cannot be delivered. [The NANC found that
> compelling LECs to query all default routed calls could impair network
> reliability, and that allowing carriers to block default routed calls
> coming into their networks is necessary to protect against overload or
> congestion that could result from an inordinate number of calls being
> routed by default to the original LEC. In light of these network
> reliability concerns, we will allow LECs to block default routed
> calls, but only in specific circumstances when failure to do so is
> likely to impair network reliability.]{.mark}
>
> **77.** [CTIA argues that the NANC\'s default routing recommendation
> will significantly, and negatively, affect CMRS providers. According
> to CTIA, even if number portability is limited initially to the
> wireline network, CMRS providers must still modify their method of
> routing calls from their customers to wireline customers who have
> ported their numbers. During the period prior to December 31, 1998,
> the date by which CMRS providers are required to have the capability
> to deliver calls to ported numbers, CMRS providers that have not yet
> implemented such capability will be required to rely on default
> routing to complete subscriber calls. CTIA argues that default routed
> calls should not be blocked, because \"\[a\]llowing incumbent LECs to
> block default routed calls when they may be acting as the only means
> of conducting a query and, thus, allowing a call to be completed,
> would discriminate against wireless carriers . . . .\"]{.mark}
>
> **78.** In the *First Report & Order*, we required CMRS providers to
> have the capability of querying number portability database systems in
> order to deliver calls from their networks to ported numbers anywhere
> in the country by December 31, 1998. We established this deadline so
> that CMRS providers would have the ability to route calls from their
> customers to a wireline customer who has ported his or her number, by
> the time a substantial number of wireline customers have the ability
> to port their numbers between wireline carriers. Under this deployment
> schedule, the initial deployment of long-term local number portability
> for wireline carriers will occur prior to the date by which CMRS
> providers must be able to perform database queries. During this
> period, CMRS providers are not obligated by our rules to perform call
> routing queries or to arrange for other entities to perform queries on
> their behalf. Thus, if wireline LECs are allowed to block default
> routed calls, calls originating on wireless networks (to the extent
> that the CMRS provider is the N-1 carrier) could be blocked. [For this
> reason, we will only allow LECs to block default routed calls when
> performing database queries on default routed calls is likely to
> impair network reliability. We also require LECs to apply this
> blocking standard to calls from all carriers on a nondiscriminatory
> basis. In the event that a CMRS or other service provider believes
> that a LEC is blocking calls under circumstances unlikely to impair
> network reliability, such service provider may bring the issue before
> the NANC. We direct the NANC to act expeditiously on these issues.
> Although CMRS providers are not responsible for querying calls until
> December 31, 1998, we urge them to make arrangements with LECs as soon
> as possible to ensure that their calls are not blocked. We note that
> if a LEC performs database queries on default routed calls, the LEC
> may charge the N-1 carrier, pursuant to guidelines the Commission will
> establish regarding long-term number portability cost allocation and
> recovery.]{.mark}

-   **NORTH AMERICAN NUMBERING COUNCIL ARCHITECTURE & ADMINISTRATIVE
    PLAN FOR LOCAL NUMBER PORTABILITY (Quoted from the document):**

> **Par. 7.10 Default Routing Overload and Failures**
>
> "Unless specified in business arrangements, carriers may block default
> routed calls incoming to their network in order to protect against
> overload, congestion, or failure propagation that are caused by the
> defaulted calls."

INTERPRETATION:

-   Regardless of the status of a carrier's obligation to provide number
    portability, e.g., has been granted a waiver or is operating outside
    a mandated area, all carriers have the duty to route calls to ported
    numbers.

> CITE:

-   **FCC NOTICE OF APPARENT LIABILITY FOR FORFEITURE, DA 04-1304,
    RELEASED MAY 13, 2004, ¶¶ 4, 13 (Quoted from the Notice):**

> **4.** Regardless of the status of a carrier's obligation to provide
> number portability, all carriers have the duty to *route* calls to
> ported numbers. In other words, carriers must ensure that their call
> routing procedures do not result in dropped calls to ported numbers.
> In this regard, the Commission stated clearly:
>
> We emphasize that a carrier operating a non-portability-capable switch
> must still properly route calls originated by customers served by that
> switch to ported numbers. When the switch operated by the carrier
> designated to perform the number portability database query is
> non-portability-capable, that carrier could either send it to a
> portability-capable
>
> switch operated by that carrier to do the database query, or enter
> into an arrangement with another carrier to do the query.

**13.** The Commission's rules are clear regarding the obligation to
route calls and to query the number portability database. Since the
*Second Report and Order* in 1997, the Commission has required the N-1
carrier to ensure that the number portability database query is
performed. No exception exists for non-LNP-capable carriers.

-   EXTENDED AREA SERVICE (EAS) CALL:

> LNPA CONSENSUS:

-   On intraLATA calls to EAS codes, the originating carrier is the N-1
    carrier and is responsible for the query on all calls to portable
    EAS codes.

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-   In cases where the originating carrier's switch supports the
    function to route interLATA EAS calls to ported numbers as a local
    call via an interLATA LRN, and trunking to all potential final
    destinations (or their POIs in the EAS area) have been established,
    the query will be performed in the originating switch.

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-   On interLATA calls to EAS codes where the originating carrier does
    not support the function to route the call as a local call to ported
    numbers via an interLATA LRN, the donor carrier in the terminating
    LATA performs the role of the N-1 carrier (i.e does the database dip
    and routes the call to the switch serving the ported number). In
    this instance, the donor carrier will perform the LNP query in the
    terminating LATA in either that carrier's donor end office or
    terminating LATA tandem, whichever terminates trunks from the
    originating LATA on calls to EAS codes. (Note that the terminating
    LATA tandem case is only applicable if the donor carrier has a
    tandem in the terminating LATA, and all switches in the originating
    LATA that can place local calls to the EAS codes in the terminating
    LATA have trunking to the tandem in the terminating LATA per
    mutually accepted interconnect agreements.) The originating carrier
    is responsible for compensation to the donor carrier for performing
    the N-1 database dip function.

> The donor carrier in the terminating LATA may charge the originating
> carrier for transit (consisting of transport and switching) of the
> call.
>
> This language takes into account current technical limitations and
> regulatory constraints as well as existing configuration issues.
> Carriers may consider making modifications to their querying and
> routing arrangements as technology upgrades and changes to
> interconnecting configurations permit.