Special Feature

Network Technology to Support PC
Communication Services
Yasushi Yamanaka†, Shuji Esaki, Akira Shibata,Shinya Takada, and Saburo Seto
Abstract
This article presents an overview of the network technology that supports the PC Communicator(PCC). It introduces several products of NTT’s R&D efforts that provide carrier-grade dependability andfunctionality (SIP server, presence server, address resolution server, billing system, and service activation system) and describes the main elements of the network architecture for the PCC system.

1. Network architecture of the PCC system
An overview of the network architecture underlying the PC communicator (PCC) [1] is shown in Fig.
1. By linking various access networks such as Internet service provider (ISP) networks, mobile service
provider networks, and the public switched telephone
network (PSTN), the PCC system makes possible
high-resolution, easy-to-use, affordable multipoint
video communication possible. It creates video andaudio connections between PCC clients using SIP(session initiation protocol) call control. It alsoenables communication between a PCC client and amobile device (a FOMA terminal) through the mobilegateway (FOMA-GW), which connects to a mobile
service provider’s gateway exchange (called IWE(interworking equipment)) [2]. The PCC system
includes several products of NTT’s R&D efforts,
which are described in the next section.
2. Network technology enabling interactive
video and audio communication
2.1 SIP server “Type1-CA (SS)”NTT has developed a SIP server with the name
Type1-CA (SS) (CA means call agent and SS indicates this is a type-1 call agent for a SIP server). It† NTT Service Integration Laboratories
Musashino-shi, 180-8585 Japan
E-mail: yamanaka.yasushi@lab.ntt.co.jp

Vol. 3 No. 10 Oct. 2005uses SIP to manage the call state and integrates thelocation server and registrar using a proxy server forconnection control. Because the SIP server complies
with SIP protocols defined in RFCs (requests forcomments) published by the IETF (Internet Engineering Task Force), it can interconnect with othercompliant SIP servers.
This SIP server supports a keepalive mechanismthat complies with draft-ietf-sip-session-timer-08: if
no new session traffic arrives before the session
expiry time, then the session is automatically considered to have timed out. This mechanism reduces
billing mistakes and clears the session state.
The SIP server was designed to meet the severe
requirements of telecommunication carriers for highdependability and functionality. Service availability
is increased through clustering, and a failover function protects existing calls from interruption whenequipment fails. Furthermore, the SIP server contains
unique features including connectivity to mobile
devices and functionality to counter DoS (denial ofservice) attacks. When a video connection is madebetween a PCC client and a mobile device, mobile
connectivity to the mobile service provider’s network
is made possible by a connection from the SIP serverto the user network interface (UNI) via FOMA-GW.
Countermeasures against DoS-attacks include functions that block packets coming from a certain IP
address if the number of packets from that address
exceeds a predefined value in a certain time period,
which minimizes the disruptive effect on legitimate
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Special Feature

PCC system
ServiceService
Billing
activation
ordersystemmanage- system“IP Service
ment “InfoBilling Configuration
system Brobcom” Control System”

Address
resolution
server“SHARE”

SIP
server“Type1CA(SS)”Operation andCommon functions maintenance functions

PresenceMultipoint
servervideo- FOMA
“Type1- conference -GW
serverCA(PS)”

End-user service
functionsIWE

ISP network
PSTN
network

PHSnetwork

PDC
network

FOMAnetwork

Access network
IAD

IP phone

IPTVphone

PCC client

Subscriber
PDC terminal
phone
FOMA terminal
PHS terminal
R&D products

Fig. 1. Overview of network architecture.

calls. Legitimate server IP addresses are registered ona white-list so that they are not mistakenly judged tobe sources of DoS attacks.

each user group and achieves independence for presence and messaging for each user group by defininga group communication policy.

2.2 Presence server “Type1-CA (PS)”The presence server Type1-CA (PS) uses SIMPLE(SIP for instant messaging and presence leveragingextensions) and, through the deployment of service
control providing presence and messaging service,furnishes the location server and registrar functions.
Like the SIP server, the presence server complies withrelevant SIP RFCs published by the IETF. Furthermore, it controls the access of requests for presence
information by providing functions for permitting or
denying the sharing of a certain user’s presence information (called “presentity”) to a watcher (a user referring to another user’s presence state).
Like the SIP server, the presence server meets thedemanding dependability and functional requirements of telecom carriers. Its clustered architecture
provides it with a failover mechanism to minimize
service interruption time when equipment fails. Furthermore, this server is equipped with NTT-developed functions for countering DoS attacks and providing tenant functions (a tenant might be a company,for example). The DoS attack countermeasures are
the same as explained above for SS. The tenant function administers the presence server’s resources for

2.3 Address resolution server “SHARE”
An overview of the address resolution method usedby PCC is given in Fig. 2. PCC uses SHARE (secureand high-performance address resolver), a high-performance, carrier-grade DNS (domain name system)
server developed by NTT, to provide secure and reliable address information. For security purposes,
SHARE can finely control the disclosure of address
information using its “user view access control” function. Furthermore, from the initial design stage, priority has been placed on creating a high level of security to guard against existing security threats such as
cache poisoning*1.
SHARE’s high performance is achieved by using
semantic division index technology*2, which canachieve many times (or many tens of times) thethroughput of BIND9, which is widely deployed as a32*1 Cache poisoning: A service attack that overwrites DNS server
entries and causes the server to return bogus IP address information to the querying client.
*2 Semantic division index technology: This technology indexes theaddress space based on the semantic structure of domain names
and telephone number, etc.

NTT Technical Review

Special Feature

User view access control function
separates the domain views seenby the user and by the operator

InternetDNS
ISP
Userside
network

DNS

Domain info
for customer

Domain info
for operator

Carrierside
network

Internal server“SHARE”:
Address resolution server

Customer terminal

Operatorterminal

Fig. 2. Overview of address resolution server “SHARE”.

Can flexibly calculate various fees(basic fee, initial fee, call charges, and campaign
discounts at end-user rates or wholesale rates.)Service ordermanagement
systemSIP server

Subscription
information
Detail accountusage data

Web-basedaccount info
systemInvoice data

Invoicingsystem

CDRs“InfoBilling Brobcom”(billing system)

FOMA-GW

Multipoint
videoconference
server

CDRs

Usage logs

Fig. 3. Overview of “InfoBilling Brobcom” billing system.

DNS server, assuming equivalent hardware and software conditions. Even if the number of domains
administered in one zone is increased to one million
entries, there is almost no degradation in performanceas the authoritative server for zone information.
SHARE supports IPv6*3, ENUM*4, and ONS*5 andit can be installed in a low-end Unix server to maximize cost performance.
2.4 Billing system “InfoBilling Brobcom”
As the billing system in the PCC system, InfoBilling Brobcom [3], which was originally developed*3 IPv6: Internet protocol version 6.
*4 ENUM (telephone number mapping): A mechanism for providing
support for telephone numbers by Internet services.
*5 ONS (object name service): A method for managing the electronic product code used by RFID (radio frequency identification) tags
and the server associated with those IDs.

Vol. 3 No. 10 Oct. 2005

for VoIP and data services, is applied to calculate fees
for the video and audio communication service andgenerate data for invoicing and about customer usage(Fig. 3). It regularly collects call detail records(CDRs) output by the SIP server and FOMA-GW andthe logs generated by the multipoint videoconference
server. It calculates usage charges based on CDRs,logs, and users’ subscription information, which is
acquired from the service order management system.
Types of charges that are calculated include monthly
basic fees, initial fees, and call charges.
By determining the type of service being provided
based on an analysis of the CDRs and logs for eachcall, InfoBilling Brobcom can calculate a wide variety of calling rates for the various interactive video
and audio communication services. It also supports
the calculation of discounts for various campaigns,
which is important for marketing strategies. Furthermore, it can calculate two types of rates: end-user
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Special Feature

Replaceable service modules increase software architecture
flexibility and shorten the development cycle for system
operations programs.
Service orderdistribution
Service ordermanagementsystem

Service order
input

Service module(individual portion)
Regis- Cancel- Password Suspen- Reinstatetration lation change sion
ment
Platform module (common portion)

SIP server

Presence
serverService activation system“IP Service Configuration Control System”

Fig. 4. Overview of service activation system “IP Service Configuration Control System”.

retail rates and wholesale rates. Retail rates are therates that an ISP charges directly to end-users, while
wholesale rates are the rates that a service wholesaler
charges to ISPs. InfoBilling Brobcom can set different rates for each ISP, and it supports flexible expansion of the number of ISPs supported by a service
wholesaler. Billing data can be converted into the various formats required by ISPs’ invoicing systems
including their Web-based account information systems.
In this way, InfoBilling Brobcom flexibly supports
the wide variety of rate calculations necessary foroffering wholesale services.
2.5 Service activation system “IP Service
Configuration Control System”
The “IP Service Configuration Control System” forinteractive video and audio communication supports
service order configurations for both the SIP andpresence servers. Various flow-through improvements have been achieved for system operations input
to both servers such as improvements in the work
flow for handling subscriber registration, password
changes, subscription cancellation, suspension, orreinstatement, and video option changes. The functions required by the service activation system vary
greatly depending on the provided services, types ofnodes, network environment, and operators’ knowhow level. Manually coding such specialized functional requirements into software would be very difficult and would increase the amount of time needed
to introduce new services. With this in mind, the IP
Service Configuration Control System was designedwith an architecture based on separating the platform
34and service layers and separating the various servicesinto distinct service modules (Fig. 4). This design
enables new services to be introduced simply by
replacing a service module.
3. Plans for the future
PCC is a service system for both point-to-point andmultipoint audio and video communication. As there
is a demand for this type of communication in thebusiness world, our efforts will focus on strengthening our suite of products for the business market andexpanding the offering to include network services
including forwarding services. For SHARE, we plan
to introduce a high-performance service for
ENUM/RFID and further strengthen its security
including providing countermeasures against DDoS
(distributed DoS) attacks. For the billing system, weplan to further expand the number of patterns for rate
calculation including patterns to support calls originating from mobile phones in order to support theFOMA-GW interface connection between networks(network-to-network interface (NNI) connection)and patterns to support charging based on the numberof calls. The IP service configuration control systemcurrently allows service order entry only in batches.
We plan to add support for realtime service order
entry, which should expand the number of applications where PCC can be used.
References[1]

T. Murakami, S. Hayama, T. Yoshida, and S. Ishibashi, “Video Communication Technology for Resonant Communication, “NTT Techni-NTT Technical Review

Special Feature[2]

cal Review, Vol. 3, No. 10, pp. 12-17, 2005.
H. Takeda, D. Ando, S. Sakauchi, S. Onishi, and H. Jozawa “Functions of PC Communicator: PC-to-FOMA IP Videophone Technology,” “NTT Technical Review, Vol. 3, No. 10, pp. 18-24, 2005.

[3]

T. Sato, K. Kanishima, S. Takada, and M. Hanaki, “Billing/Settlement Platform “InfoBilling BrobCom” for VoIP and Data Services,”
NTT Technical Review, Vol. 1, No. 1, pp. 73-77, 2003.

Yasushi Yamanaka

Shinya Takada

Senior Research Engineer, Supervisor, NTT
Service Integration Laboratories.
He received the B.E. and M.E. degrees in engineering from Kyushu University, Fukuoka in
1981 and 1983, respectively. He joined Yokosuka Electrical Communication Laboratories, Nippon Telegraph and Telephone Public Corporation (now NTT) in 1983. He has been engaged in
R&D of subscriber transmission systems andtelecommunication management systems. Currently, he is working on the verification of IP
video communication systems and SIP interoperability testing for the next-generation network.
He is a member of the Institute of Electronics,
Information and Communication Engineers(IEICE).

Research Engineer, Network Application Platform Project, NTT Information Sharing PlatformLaboratories.
He received the B.S. and M.S. degrees inphysics from University of Tokyo, Tokyo in
1996 and 1998, respectively. In 1998, he joined
NTT Software Laboratories, Tokyo. His current
research area is billing-related systems, especially usage-related aspects.

Shuji Esaki

Engineer, Network Management Development
Project, Second Promotion Project, NTT Network Service Systems Laboratories.
He received the B.S. and M.S. degrees in information science from the University of Tokyo,
Tokyo in 1996 and 1998, respectively. In 1998,
he joined NTT Network Service Systems Laboratories, Tokyo. Since then, he has been engaged
in developing operation support systems.

Senior Manager, Network Development Division, Service Development Department, NTT
Resonant, Inc.
He received the B.E. and M.E. degrees in engineering from Osaka University, Osaka in 1984
and 1986 respectively. Since joining NTT in1986, he has engaged in R&D of the intelligent
network. From 1999 to 2002, he worked on thedevelopment of the commercial IP network service systems in NTT West corporation. After
returning to NTT in 2002, he worked on developmental research on the multimedia communication service systems. He moved to NTT Resonant Inc. in 2004 and is active in IP communication systems including VoIP. He is a member ofIEEE, IEICE, and the Information Processing
Society of Japan.

Saburo Seto

Akira Shibata
Senior Research Engineer, Communication
Platform SE Project, NTT Information Sharing
Platform Laboratories.
He received the B.E. and M.E. degrees in electrical engineering from Waseda University,
Tokyo in 1991 and 1993, respectively. In 1993,
he joined NTT Communication Switching Laboratories, Tokyo. Since then, he has been engaged
in R&D of intelligent network systems, IP network service systems and next-generation network service systems. He is currently engaged inR&D of secure and high-performance DNS systems. He is a member of IEICE.

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