Distribution of Numbering Information in Interconnected Circuit and Packet Switched Networks

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Distribution of Numbering Information in
Interconnected Circuit and Packet Switched
Networks
Nicklas Beijar Nicklas.Beijar_at_hut.fi Networking
Laboratory Helsinki University of Technology P.O.
Box 3000, 02015 HUT, Finland Masters Thesis
HUT, Networking Laboratory, Espoo,
2002 Supervisor Prof. Raimo Kantola Presentation
S-38.360 Research Seminar, 25.2.2002
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Agenda

• Agenda

• Background (Number portability, TRIP, ENUM)
• Motivation and goals
• Architecture
• The CTRIP protocol
• Scenario based on TRIP/CTRIP
• CTRIP and TRIP attributes
• Numbering gateway
• Results
• Conclusions

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Background

• 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

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Background

• 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 -gt 3.0.3.5.1.5.4.9.8.5.3.e164.
arpa
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Background

• 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

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Motivation

• 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

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Goal

• 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

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Application-layer routing
Application layer
358-9-4321253
358-9-4514563
358-9-2315532
E.164 Directory numbers
Network layer
54.75.43.7
98734532
9872346
98734232
147.12.6.125
34.65.43.2
97798234
124.65.3.32
Routing numbers
IP-addresses
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Reference architecture
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CTRIP

• 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

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Protocol connections
TAD 2 (IP)
TAD 1 (IP)
TAD 3 (SCN)
RP1
GW2
GW1
RP6
TAD 5 (SCN)
RP2
TAD 4 (SCN)
RP3
RP4
RP5
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Routes formed by TRIP/CTRIP
TAD 2 (IP)
TAD 1 (IP)
987 GW2 (3,SCN)
987 SS2 (2,IP),(3,SCN)
TAD 3 (SCN)
RP1
GW2
GW1
RP6
TAD 5 (SCN)
RP2
TAD 4 (SCN)
RP3
987 RP6 (1,IP),(2,IP), (3,SCN) 987
RP5 (5,SCN),(3,SCN)
RP4
RP5
987 RP3 (3,SCN)
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Route 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

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TRIP attributes
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CTRIP attributes
Modified
Modified
New
New
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CTRIP attributes
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, DPCSSN)
• Directory number modified with regex
• Other parameters

New
New
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CTRIP attributes
Modified
Modified

• List of path segments
• Type (unordersed/ordered)
• List of hops
• TAD identifier
• Application protocol (e.g. SIP, H.323, SCN)

New
New
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CTRIP attributes
Modified
Modified
Indicates the originating protocol (ENUM or TRIP)
for a route to an IP terminal
New
New
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CTRIP attributes
Modified
Modified
For synchronizing moving numbers
New
New
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TRIP attributes
New
New
New
Extended routed path
Path for signaling (compatible with
CTRIP)
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Numbering gateway

• 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

independent of ownership
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Routing 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

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Results

• Litterature research on routing in SCN and IP
  networks, number portability, TRIP and ENUM
• 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
• A basic implementation was made to verify the
  central concepts

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Conclusions

• 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

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Conclusions

• 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

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Conclusions

• CTRIP and TRIP provide a common protocol for
  distributing routing
• information 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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Thank you for your attention! Questions?