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A Cooperative SIP Infrastructure for Highly Reliable Telecommunication Services

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Title: Part I: Introduction Author: Don Towsley Last modified by: Ali Fessi Created Date: 10/8/1999 7:08:27 PM Document presentation format: Bildschirmpr sentation – PowerPoint PPT presentation

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Title: A Cooperative SIP Infrastructure for Highly Reliable Telecommunication Services


1
A Cooperative SIP Infrastructure for Highly
Reliable Telecommunication Services
  • Ali Fessi, Heiko Niedermayer,
  • Holger Kinkelin, Georg Carle
  • IPTComm 2007, 19th-20th July, New York, USA

2
Overview
  • Motivation
  • Properties of server-based SIP networks
  • Properties of P2P-based SIP networks
  • Our solution for SIP reliability Cooperative
    SIP (CoSIP)
  • CoSIP Overview
  • Sample Applications
  • Implementation
  • Evaluation
  • Improving reliability and security with CoSIP
  • Initial functional tests results
  • Conclusions

3
Motivation
  • Some open issues with VoIP still need to be
    solved
  • reliability, security, QoS, SPIT, etc.
  • Users are used to the nearly 100 reliable PSTN
  • Good news
  • Peer-to-peer (P2P) networks provide higher
    reliability
  • Bad news
  • P2P network have also their bad side
  • Security in P2P networks is much harder to cope
    with due to decentralization
  • Goals
  • How can we make SIP networks more reliable?
  • How can we benefit from the advantages of both
    architectures
  • server vs. P2P

4
Properties of Server-based SIP Networks
  • Sufficient security mechanisms
  • UA authentication
  • Integrity and confidentiality
  • High lookup performance of SIP URI
  • O(1) messages
  • Complex service infrastructure
  • SIP proxies, registrars, AAA servers, location
    database, DNS server, routers, etc
  • Network and service failures may propagate
    quickly
  • Server infrastructures are vulnerable to DoS
    attacks

5
Properties of P2P-SIP Networks
  • Self-organization
  • Recoverability from local failures
  • Robustness against DoS attacks
  • ? P2P network can also survive under
    difficult conditions
  • Scalability
  • Lookup performance of the Contact URI in a DHT in
    the avg case
  • O( log ( N ) ) messages N is the number of peers
  • Several security issues can not be solved in
    pure P2P network
  • Attacks on the routing of lookup requests
  • Attacks on the content of the P2P network
  • Sybil attacks, partitioning attacks, etc.
  • Open P2P-SIP networks are an invitation for SPIT!

6
Cooperative SIP (CoSIP)
  • Basic idea
  • Design a hybrid architecture that benefits from
    the advantages of both server-based and P2P-based
    SIP networks
  • SIP User Agents organize themselves into a P2P
    network
  • SIP infrastructure and SIP User Agents cooperate
    in order to provide the best service
  • ? Cooperative SIP architecture CoSIP
  • Improve reliability, survivability, security and
    lookup performance

7
CoSIP UA Registration
  • A SIP UA is registered to the SIP infrastructure
    as well as to the DHT
  • Use REGISTER for registration to the
    infrastructure
  • Use put for the registration to the DHT
  • put (H(SIP_URI), Contact_URI)

REGISTER
put(H(SIP_URI), Contact_URI)
8
CoSIP Session Establishment
  • Signaling to the SIP infrastructure with INVITE
  • In parallel resolve the Contact-URI in the DHT
    with a get
  • get (H(SIP_URI)) Contact_URI
  • Server does not answer or DHT is faster?
  • ? use the Contact-URI provided by the DHT
    lookup
  • ? perform direct signaling to the peer
  • Lookup performance
  • under normal conditions
  • O(1) messages
  • in case of failures of the infrastructure
  • O( log ( N ) ) messages

INVITE
get(SIP_URI)
INVITE
Session
200 OK
Contact_URI
9
CoSIP Sample Applications
  • Large enterprise/ academic SIP networks with e.g.
    20-30 k-users
  • CoSIP can be used to bridge
  • network and service failures
  • maintenance downtimes

CoSIP-enabled SIP Network
10
CoSIP Sample Applications (2)
  • CoSIP adapter/ proxy in DSL routers
  • CoSIP adapters organize themselves into a P2P
    network

Small Office and Home Network (SOHO)
Internet/VoIP Provider
DSL Router with a CoSIP adapter / CoSIP proxy
SOHO
11
Implementation of CoSIP as an external Proxy
Application
SIP Express Router (SER)
  • The CoSIP proxy is an adapter to connect regular
    SIP UA
  • CoSIP Proxy communicates with the SIP
    infrastructure and the P2P network
  • DHT Bamboo/ Pastry
  • Formal specification of the CoSIP protocol
    with SDL
  • Programming language Python
  • When the SIP infrastructure fails P2P signaling
    between the CoSIP proxies

12
Specification of CoSIP - Goody
  • State machines switchable to different modes
  • Cooperative mode (DHT SIP server)
  • DHT-only mode (basically P2P-SIP with Bamboo as a
    DHT)
  • Server-only mode
  • DHT-only mode successfully tested with OpenDHT

13
SIP UA running with CoSIP Proxy in the background
14
Evaluation
  • Improving reliability with CoSIP
  • P2P network provide high reliability and
    self-organization
  • Local failures can be recovered autonomically by
    neighboring peers
  • Data is replicated on a set of nodes (replica
    set)
  • Even large failures affect only a part of the
    network
  • In the ideal case (uncorrelated failures), the
    probability of a service failure with CoSIP would
    be
  • ? CoSIP provides even better reliability and
    survivability than
  • P2P-SIP networks
  • server-based SIP networks

15
Evaluation
  • Improving security with CoSIP
  • Managing security in large P2P-SIP networks is
    not possible without central severs
  • However, PKI / CA is not enough
  • A CA is not able to detect an attack in the P2P
    network and shut down the attacker
  • A security solution for P2PSIP requires
  • more SIP specific knowledge
  • knowledge about the P2P network
  • CoSIP servers can provide Identity Management for
    the P2P-SIP network
  • CoSIP servers can make sure that peers in the
    P2P-SIP network behave well
  • How can you provide Intrusion Detection in a
    large P2P network?
  • ? a CoSIP server can help to do this job
  • More work is still required on this topic

16
Evaluation
  • Initial tests have been run on PlanetLab
  • Each used PlanetLab node hosts
  • a SIP UA
  • a CoSIP proxy
  • a Bamboo DHT node
  • High variance of the RTT on PlanetLab noticed
  • SIP server failure emulated
  • Successful recoverability from service failure
  • No interruption of service is noticed
  • Time required to establish a session between UAC
    and UAS increases slightly but is still
    acceptable
  • Performance results will be published soon

17
CoSIP Summary
  • CoSIP provides a low-cost solution for
    significantly improving the reliability of SIP
    networks
  • Implementation
  • CoSIP as an external proxy application ?
    compatible to existing SIP networks
  • Cooperative (server DHT) as well as DHT-only
    mode possible
  • CoSIP is a hybrid architecture which provides
    better reliability, survivability, security and
    performance simultaneously
  • Could CoSIP be useful for catastrophic failures /
    emergency calls?
  • Future work
  • Integration of security mechanisms to CoSIP ?
    Improve security of P2P-SIP
  • CoSIP is still a single domain concept ?
    Peering of several domains with CoSIP
  • Improving geometry and routing in the DHT for
    higher connectivity in case of network failures

18
Questions / Discussion / Feedback
19
P2P-SIP
  • Basic idea SIP without server
  • Registration
  • Phase1 Node registration P2P-SIP node joins
    the DHT
  • Phase 2 User registration storing the Contact
    URI with SIP URI as lookup key in the DHT
  • Session establishment
  • Resolving the SIP URI to a Contact URI using the
    DHT
  • Subsequent signaling can occur between the two
    peers

Node registration
User registration
Session establishment
20
Evaluation - PlanetLab
  • Global research network
  • 784 nodes
  • 382 institutions
  • Cons
  • Very variable performance and load of PlanetLab
    nodes
  • High variance in the RTT
  • ? Causes high variance in the measurement
    results
  • High instability and unreliability of the
    PlanetLab nodes
  • Upgrade PlanetLab 3.0 to 4.0
  • More than 50 nodes barely manageable

21
CoSIP State Machines
  • Formal specification of the CoSIP protocol using
    SDL
  • Logical separation between the state machines of
    different SIP UAs
  • The CoSIP proxy processes
  • requests from UA
  • messages from the server
  • messages from the DHT
  • timeouts for limiting the pending time
  • Events are processed FIFO

SDL diagram for the processing of an INVITE
message in state IDLE
22
CoSIP State Machines (2)
High Level INVITE Session State Machine
High Level REGISTER Session State Machine
23
Related Work
  • P2PSIP
  • Secure Overlay Services (SOS)
  • Resilient Overlay Networks (RON)
  • Skype
  • CoDNS

24
Overview Tesbed
25
OpenDHT
  • OpenDHT Bamboo running on PlanetLab
  • publicly accessible
  • put
  • get
  • remove

26
CoSIP Implementation Overview
  • Threading for transport of SIP messages
  • and communication with the DHT
  • Event-based processing of
  • SIP messages
  • DHT messages
  • Timeouts
  • Events are processed
  • FIFO
  • Programming language
  • Python
  • Platform independent
  • (CoSIP tested with Linux / Windows)
  • Code size ca. 5 kLoC

27
SIP UA running with CoSIP Proxy in the background
28
Evaluation Recovery from Service Interruption
29
Evaluation (VI)
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