Slide 1 Nicklas Beijar - Distribution of Numbering Information in Interconnected Circuit and Packet...

Nicklas Beijar - Distribution of Numbering Information in Interconnected Circuit and Packet Switched Networks

Distribution of Numbering Information in Distribution of Numbering Information in Interconnected Circuit and Packet Switched NetworksInterconnected Circuit and Packet Switched Networks

Distribution of Numbering Information in Distribution of Numbering Information in Interconnected Circuit and Packet Switched NetworksInterconnected Circuit and Packet Switched Networks

Nicklas [email protected]

Networking LaboratoryHelsinki University of Technology

P.O. Box 3000, 02015 HUT, Finland

Master’s Thesis: HUT, Networking Laboratory, Espoo, 2002Supervisor: Prof. Raimo Kantola

Presentation: S-38.360 Research Seminar, 25.2.2002


1. Background (Number portability, TRIP, ENUM)2. Motivation and goals3. Architecture4. The CTRIP protocol5. Scenario based on TRIP/CTRIP6. CTRIP and TRIP attributes7. Numbering gateway8. Results9. Conclusions

Agenda

AgendaAgendaAgendaAgenda


TRIP (Telephony Routing over IP)• IETF protocol, still at draft stage• Inter-domain protocol between Internet Telephony Administrative Domains (ITAD)• Distributes routing information between location servers

• Information about gateways and the numbers reachable through them• Routes to gateways and signaling servers

• Interdomain distribution modeled after BGP-4• Gateway selection driven by policies• Intra-domain synchronization based on SCSP and OSPF• Information transported as attributes of the UPDATE message• Expandable

Locates the most suitable gateway for a given call

BackgroundBackgroundBackgroundBackground


ENUM (tElephone NUmbering Mapping)• RFC 2916• Maps E.164 numbers into Uniform Resource Identifiers (URI)• The URIs represent different ways to contact a host

• SIP, H.323, TEL, email, ...• Uses the Domain Name System (DNS)

• E.164 number rewritten as a domain name:

• Provides simple number portability

Locates a terminal with a given E.164 number on the IP network

+358-9-4515303-> 3.0.3.5.1.5.4.9.8.5.3.e164.arpa



Number portability• Change service provider, location or service type without changing telephone number• Implemented with IN (Intelligent Network)• Separate directory numbers and routing numbers• Number portability required for IP networks• Number portability between SCN and IP network

• Operator may move subscribers to its IP telephony network

Increasing management burden• More services• More service providers• SCN and IP network with several signaling protocols



MotivationMotivationMotivationMotivation

• SCN and IP telephony networks will co-exist• Management is becoming more complex due to

• IP telephony• number portability• increasing number of services• increasing number of operators• new mobile networks

• Number portability is required between SCN and IP networks• Media conversions in gateways should be avoided• TRIP routes are currently configured manually• Gateway selection for calls SCN IP is still done manually• The information in IN, TRIP and ENUM must be kept synchronized• Automatic routing based on policies instead of static routes

A routing protocol is required


GoalGoalGoalGoal

Main goal: To examine how a routing protocol can be utilized for distribution of numbering information in an interconnected SCN and IP network

The TRIP protocol selected as basis

In the thesis:• The architecture for distribution of numbering information is developed• A new protocol named CTRIP (Circuit Telephony Routing Information Protocol) is developed as a counterpart to TRIP• The numbering gateway is defined• Scenarios and applications are examined


Application-layer routingApplication-layer routingApplication-layer routingApplication-layer routing

SS

Gateway

Application layer

Network layer SS SS

Routing numbersIP-addresses

E.164 Directory numbers

34.65.43.2

54.75.43.7

124.65.3.32

98734232147.12.6.125

98734532

97798234

9872346

358-9-4514563

358-9-4321253

358-9-2315532


IP-networkITAD

IP-networkITAD

SCN networkCTAD

SCN networkCTAD

CTRIP node(SDF, switch, ...)

TRIP node(location server)

Reference architectureReference architectureReference architectureReference architecture

External peer

Internal peer

External peer

TRIPCTRIP

CTRIP node(SDF, switch, ...)

TRIP node(location server)

Numbering gateway

Numbering gateway


CTRIPCTRIPCTRIPCTRIP

CTRIP (Circuit Telephony Routing Information Protocol)• Counterpart of TRIP for the SCN• Similar protocol as TRIP, new attributes added

Purpose• Inter-domain distribution between networks

• Routes are formed based on the policies of the network• Aggregation to reduce information amount and to hide topology details

• Intra-domain synchronization within the networks• All routing databases in a domain contain identical information

• Provides automatic selection of gateways between IP and SCN• Collects information about the SCN for distribution with TRIP


SS1 SS2

TAD 2 (IP)

TAD 5 (SCN)

TAD 3 (SCN)

TAD 1 (IP)

TAD 4 (SCN)

RP1

RP2

RP3

RP5 RP4

RP6

GW1

GW2

CTRIP

TRIP TRIPTRIP

CTRIP

CTRIPN G

N G

Protocol connectionsProtocol connectionsProtocol connectionsProtocol connections


SS1 SS2

TAD 2 (IP)

TAD 5 (SCN)

TAD 3 (SCN)

TAD 1 (IP)

TAD 4 (SCN)

RP1

RP2

RP3

RP5

987: SS2 {(2,IP),(3,SCN)}987: SS2 {(2,IP),(3,SCN)}

987: GW2 {(3,SCN)}987: GW2 {(3,SCN)}

987: RP6 {(1,IP),(2,IP), (3,SCN)}987: RP5 {(5,SCN),(3,SCN)}

987: RP6 {(1,IP),(2,IP), (3,SCN)}987: RP5 {(5,SCN),(3,SCN)} 987: RP3

{(3,SCN)}987: RP3 {(3,SCN)}

987xxxxx

RP4

GW2

Routes formed by TRIP/CTRIPRoutes formed by TRIP/CTRIPRoutes formed by TRIP/CTRIPRoutes formed by TRIP/CTRIP

CTRIP

TRIP TRIPTRIP

CTRIP

CTRIP

RP6N G

N G

GW1


Route selectionRoute selectionRoute selectionRoute selection

Selection performed by policy functions• Defined for each network (TAD)• Calculates a preference value based on the attributes• Highest preference route for each prefix selected

Selection based on attributes• The operators on the path• Number of intermediate network• The type of the intermediate networks (SCN/IP)

• Used to minimize numbers of media conversions• The signaling protocols on the path• Properties and capabilities of the gateways• Cost• New attributes can be added


Name Description

Withdrawn routes List of telephone numbers that are no longer available.

Reachable routes List of reachable telephone numbers.

Next hop server The IP address of the next hop signaling server.

Advertisement path The path that the route advertisement has traveled. Loop avoidance.

Routed path Path for signaling.

Atomic aggregate Indicates that the path can contain networks not included in Routed Path.

Local preference The intra-domain preference of the route.

Multi exit disc The inter-domain preference of the route if several links are used.

Communities For grouping destinations in groups with similar properties.

Domain topology For advertising the ITAD topology to other servers in the same ITAD.

Converted route Indicates that the Application Protocol has been converted.

TRIP attributesTRIP attributesTRIP attributesTRIP attributes


Name Description



Next hop address The network and routing number pattern of the next hop.







IP destination Indicates the origin of the route to a prefix on the IP network.

Number portability state Indicates the state of a moving number.

Domain topology For advertising the TAD topology to other servers in the same TAD.


CTRIP attributesCTRIP attributesCTRIP attributesCTRIP attributes

New

New

Modified

Modified


Name Description















New

New

Modified

Modified

1. Routing number• Generated with a regular expression from the directory number

2. Query to obtain routing number• Protocol (LDAP, INAP, MAP)• Address (IPv4, IPv6, DPC+SSN)• Directory number modified with regex• Other parameters


Name Description















New

New

Modified

Modified

List of path segments:• Type (unordersed/ordered)• List of hops:

• TAD identifier• Application protocol (e.g. SIP, H.323, SCN)


Name Description















New

New

Modified

Modified

Indicates the originating protocol (ENUM or TRIP) for a route to an IP terminal


Name Description















New

New

Modified

Modified

For synchronizing moving numbers


Name Description



Next hop server The IP address of the next hop signaling server.











TRIP attributesTRIP attributesTRIP attributesTRIP attributes

New

Extended routed path Path for signaling (compatible with CTRIP)New

New


Purpose • Translates between TRIP and CTRIP• Inserts the gateway on the path

Design principles• Simple because of similarity between TRIP and CTRIP• Well defined• No policies• Can be integrated into a TRIP or CTRIP node• Transparent to its peer nodes

Numbering gatewayNumbering gatewayNumbering gatewayNumbering gateway

CTRIPTRIP

CTRIP

CTRIP

CTRIP

Numbering gateway CTRIP

TRIPCTRIP

CTRIP

CTRIP

independent of ownership}


Routing with TRIP/CTRIPRouting with TRIP/CTRIPRouting with TRIP/CTRIPRouting with TRIP/CTRIP

Application layer routing protocol• Addressing: E.164 directory numbers• Forms a new layer above the network layer

Next Hop Address• TRIP: IP address of the next signaling server or gateway• CTRIP: Regular expression for generating routing number based on the directory number• CTRIP supports INAP, LDAP and MAP queries

Aggregation reduces information• Sequence of prefixes with same properties can be combined to a single shorter prefix• Hides topology details


1. Litterature research on routing in SCN and IP networks, number portability, TRIP and ENUM

2. Development of a solution The architecture was defined The CTRIP protocol was developed Some new attributes were added to TRIP The numbering gateway was defined Applications and usage scenarios were examined

3. A basic implementation was made to verify the central concepts

ResultsResultsResultsResults


Advantages Simplifies management of routing information

• Increasing load due to more services, more service providers, number portability• Simplifies movement to IP based technology

Automatic• Generates routes between networks and network technologies• Generates the TRIP information at its source

Policy based• General policy functions can be defined centrally

ConclusionsConclusionsConclusionsConclusions


Advantages (cont.)

Based on a routing protocol• Responds to changing network conditions• Searches for optimal paths and most suitable gateway

Reduces number of media/signaling protocol conversions• For example in a IP to SCN call where the B-number has ported to an IP network and the originating network is not aware of it

Allows for number portability between SCN and IP networks

Expandable protocol• New attributes can be added to describe the routes and gateways



CTRIP and TRIP provide a common protocol for distributing routinginformation on the SCN, the IP network and between them

Further work• Implementation and testing of TRIP, CTRIP and numbering gateway• Testing with real scenarios, scalability testing• Development of location server and integration with SIP clients



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