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Course on future signaling protocols in 3G networks SIP and All-IP in Fixed and Mobile Networks, Merito Forum, 28-29 April 2003.
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1 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Future Signaling Protocols
What’s New in IETF
John Loughney
Research Manager
Nokia Research Center
2 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Contents
• Part 1• Migration from SS7 to IP signaling.• SIGTRAN, SIP & ISUP interworking• SCTP, uses on the Internet and within 3G networks.
• Part 2• AAA and Diameter• SeaMoby• Towards hybrid 3G networks with WLAN and IP networks
3 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
SIGTRAN Documents
• Standards• Architectural Framework for Signaling Transport - RFC 2719• ISDN Q.921-User Adaptation Layer - RFC 3057• SCTP Applicability Statement – RFC 3257• Signaling System 7 (SS7) MTP2 - User Adaption Layer – RFC 3331• SS7 MTP3-User Adaptation Layer (M3UA) – RFC 3332
• In IESG Review• SS7 SCCP-User Adaptation Layer (SUA)• Stream Control Transmission Protocol Management Information Base• SS7 MTP2-User Peer-to-Peer Adaptation Layer• IUA Outstanding Issues
• Under Discussion• Telephony Signalling Transport over SCTP applicability statement• SS7 MTP3-User Adaptation Layer Management Information Base • V5.2-User Adaption Layer (V5UA) • DPNSS/DASS 2 extensions to the IUA protocol • M3UA Implementer's Guide
4 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
SIGTRAN in 3GPP
• Release 99 Packet Architecture• RANAP (Iu interface) – M3UA / SCTP• RNSAP (Iur interface) - M3UA / SCTP
• Rel 4 & 5 - All IP architecture• MAP over 'SIGTRAN‘ (M3UA / SCTP)• CAP over 'SIGTRAN‘ (M3UA / SCTP)• BICC over 'SIGTRAN‘ (M3UA / SCTP)
5 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
SIGTRAN Network
6 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
SIGTRAN in Industry
• Major protocol vendors supporting SIGTRAN protocols• HSS• Trillium/Intel• Ulticom
• Conformance tests• NetTest• Etherreal
• Several Public Conformance Test Events• M3UA bake-off, held in Madrid, Spain May 7-11, 2000.• M2PA interop, held in November 2001 .• SUA v08 interop held in Belgium in November 2001.• M3UA interop held by ETSI, February 2002.• SigTran interop held by ETS, October 2002.
7 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Backhaul
SP
SS7 stack
SP
UA
SCTP
IP
UA
SCTP
IP
SS7 stack
SEP SG SEP
Traditional telephony signaling
Telephony signaling over IP
SEP: Signaling Endpoint SG: Signaling GatewayISEP: IP Signaling Endpoint SP: Signaling ProtocolUA: User Adaptation Layer SCTP: Stream Control Transport Protocol
8 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Communication Within IP Networks
SP
UA
SCTP
IP
SEP
SP
UA
SCTP
IP
SEP
Telephony signaling over IP
IPSP: IP Signaling Point.
9 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
PSTNIP
SIP & ISUP Interworking
Media GatewayMGW
E1/T1User plane (RTP)
SS7 (SCCP, TCAP) over IP (Sigtran)Transit SignallingGateway T-SGW
SS7 (SCCP, TCAP)
MGCF
SIP (ISUP) to CPS SS7 (ISUP)
10 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Network View
11 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
SCTP Features and Properties
• Connection-oriented, robust, reliable transport - similar to TCP.
• Support of multi-homing for enhanced reliability.• Endpoints are identified by sets of IP addresses / ports• Not by IP address / port pairs, like TCP.
• Enhanced initiation routines to prevent spoofing & DoS attacks.
• Logically independent streams, managed under a single set of congestion controls) which prevent head-of-line blocking (each stream is similar to a single TCP connection).
• The benefit of this over multiple TCP connections is that the user does not have to manage separate connections.
• Current best thinking applied to congestion management.
12 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
SCTP Standards
• Standards• Stream Control Transmission Protocol - RFC 2960 • SCTP Applicability Statement – RFC 3257• An Introduction to SCTP – RFC 3286 • SCTP Checksum Change - RFC 3309• Transport Layer Security over SCTP – RFC 3436
• Waiting Publication• On the Use of SCTP with IPsec
• Under Discussion• SCTP Implementors Guide• Sockets API Extensions for SCTP• Requirements for RoHC IP/SCTP Robust Header Compression • PR-SCTP (Partial Reliability SCTP)• SCTP Dynamic Address Reconfiguration• SCTP MIB
13 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Why?
• IP is 'everywhere' but it an 'old' protocol (RFC 793 September 1981)
• TCP has acknowledged deficiencies.• Head-of-line blocking• Vulnerable to attacks• Poor support for multihoming.
• New demanding networks, applications & services are IP based.• IP Telephony• Streaming Audio & Video• 3G• Advancing Hardware Design• Bandwidth, bandwidth, bandwidth ...
(reliability, reliability, reliability)
14 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
SCTP Goals
• SCTP is designed to transport both PSTN signaling messages and provide general transport solution.
• SCTP is an kernel-level datagram transfer protocol operating over IP offering:
• acknowledged error-free non-duplicated transfer of user data
• data segmentation to conform to discovered path MTU size,• sequenced delivery of user datagrams within multiple streams, with an
option for order-of-arrival delivery of individual messages• optional multiplexing of user messages into SCTP datagrams, subject to
MTU size restrictions• network-level fault tolerance through supporting of multi-homing at either
or both ends of an association.
• Appropriate congestion avoidance behavior.
• Resistance to flooding and masquerade attacks.
15 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Differences between TCP & SCTP
• SCTP is connection-oriented in nature, but the SCTP association is a broader concept than the TCP connection.
• The term "stream" is used in SCTP to refer to a sequence of user messages. This is in contrast to its usage in TCP, where it refers to a sequence of bytes.
16 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Current Deployment Level
• First major deployment will be with the initial deployment of UMTS networks.
• Protocols Transported over SCTP• SS7 over IP (SIGTRAN)• Diameter (AAA)• SIP• BICC
• Future Support• ISCSI – called IP Storage by the IETF• Remote Direct Memory Access - called RDDP by the IETF• Reliable Server Pooling protocols• CORBA
17 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
SIP over SCTP
• Use of SIP over UDP is deprecated.
• Advantages of SCTP over UDP • Fast Retransmit • Congestion Control • Transport layer fragmentation
• Advantages of SCTP over TCP • Prevention of Head of the Line Blocking• Easier parsing due to SCTP’s message based nature.• Multihoming support adds protection against network failure.
• Summary• Under a zero loss condition, SCTP transport of SIP should
perform on par with TCP transport. • Under loss conditions, SCTP should perform better than
TCP.
18 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Part 2
• Diameter / AAA (Authentication, Authorization & Accounting)
• SeaMoby (Seamless Mobility)
• NSIS (Next Steps in Signaling)
19 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
AAA & Diameter
• Next generation Authentication, Authorization & Accounting protocol
• Consists of base specification and applications• MIP• Network Access Server (Dial-up / PPP / SLIP environment)• SIP Services• Accounting Extensions
20 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Standard RADIUS Model
21 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Diameter Roaming
22 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
How It Works
• The user requests service from the remote ISP, which in tern requests the user’s credentials.
• The user submits ID, password and address of his home-agent. The remote server performs mutual authentication with the home-agent and forwards the user’s credentials.
• The home-agent accepts the user’s credentials and then tells the remove ISP to grant access to the user.
• Subsequently, the two ISPs update their call accounting records.
23 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
AAA Elements
• Diameter Node • A host that implements the Diameter protocol, and acts either as a
Client, Agent or Server.
• Broker • A business term used in AAA infrastructures. A broker is either a relay,
proxy or redirect agent, and operated by roaming consortiums.
• Diameter Agent • A host that provides either relay, proxy, redirect or translation services.
• Diameter Client • A device at the edge of the network that performs access control. An
example of a Diameter client is a Network Access Server (NAS) or a Foreign Agent (FA).
• Diameter Peer • Node to which a given Diameter Node has a direct transport connection.
• Diameter Server • A server that handles authentication, authorization and accounting
requests for a particular realm.
24 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Diameter Connections and Sessions
Server Serverrelay
Peer connection A Peer connection B
User session X
NASHome Server
Translation Agent
RADIUS Req Diameter Req
RADIUS Ans Diameter Req
Translation of RADIUS to Diameter
25 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Diameter Proxy Example
NetworkAccess Server
Primary Proxy Server
Backup Proxy Server
Primary Home Server
Backup Home Server
local service provider
home service provider
26 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Diameter Extensibility
• Diameter tries to preserve Radius-like flexibility
• Diameter base commands and AVPs defined in the base spec
• Diameter extension can define new commands and AVPs.
• Examples are:• NASREQ• MOBILE-IP• 3GPP Credit Control• 3GPP Multimedia Application
• New AVPs can be added
27 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
AAA-SIP in 3GPP Rel. 5
SGW
UE P-
CSCFI-
CSCF
MGCF
Gm Mw Mw
SLF
Dx Cx
HSS AS
Cx
MGW
Mc
Mj
Mi
SIP
SIP
Diameter
Megaco
Mr
MRFC
GGSN
GoCOPS for
Policy Control
Sh
Visited
Domain
Home
Domain
ISC
MRFP
Megaco
SIP-ISUP
Compression
S-
CSCF
BGCF
Diameter
Diameter
28 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Work to Do
• Diameter Base Specification ready for publication.
• Diameter NASREQ Application nearly ready for publication.
• Diameter Mobile IPv4 Application nearly ready (needed by 3GPP2).
• SIP-AAA Requirements nearly ready.
• CMS Security Application, needed for e2e security
• Diameter Multimedia Application (3GPP rel. 6)
• Diameter Credit Control Application (3GPP rel. 6)
• AAA Key Distribution.
• Diameter Mobile IPv6 Application open.
29 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Summary
• Integrating different access technologies (3G, WLAN, DSL, Dial-up):
• increases the potential for increasing subscribers.• increases accesses to services.
• Integrating/harmonizing signaling:• harmonizes network infrastructure.• simplifies network management.• simplifies charging/billing.• simplifies the user experience.
30 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
SeaMoby Status
• Standards• Dormant Mode Host Alerting Problem Statement - RFC 3132• Requirements and Functional Architecture for an IP Mobile
Node Alerting Protocol - RFC 3154• Problem Description: Reasons For Performing Context
Transfers Between Nodes in an IP Access Network - RFC 3374
• In Review• General Requirements for a Context Transfer• Issues in CAR Discovery for seamless IP-level handoffs • Requirements for CAR Discovery Protocols • Mobility Related Terminology
• Under Discussion• Context Transfer Protocol• Candidate Access Router Discovery Protocol
31 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Context Transfer Solutions
• ICMP/UDP-based context transfer.• Efficient• Enables smoother handoffs.• Easily to integrate with MIP.
• Well-known Transport Protocol (TCP / SCTP).• May need engineered access network (i.e. – cellular)• Applicable for more than just handoff signaling?
32 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Mobile IPv6 with Context Trasfer
• Current mobile IP (v4 or v6) specifications are not alone sufficient to construct a network that offers VoIP type of services (real time requirements, no packet loss) with mobile nodes changing their point of attachment frequently.
• Smooth handover == low loss
• Fast handover == low delay
• Seamless handover == smooth and fast
• Following things to transfer• header compression• buffer management• AAA / Security information• QoS sessions
33 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Context Transfer Framework
New RouterPrevious Router
CT Request
Public internet
CT Ack
Home Agent Correspondent
node
34 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
The Future?
• What do we see that is useful for SeaMoby to solve?
• Smooth, seamless Mobile VoIP.• Inter-technology handovers.• Operator – ISP handovers (Cellular – WLAN handovers).• Adding additional IP technology to ‘existing’ cellular
architecture.
35 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Next Steps In Signaling
• Work on a next generation signaling protocol.
• Re-use good parts of RSVP, while optimizing it (RSVP is used heavily in MPLS signaling.)
• Make the signaling protocol generic, to support multiple services.
• Useful for signaling entities along the data path (NATs, firewalls, resource entities, etc.)
36 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Main Ideas
• Decouple (QoS) signaling (i.e. – requesting) from resource reservation.
• Signal not just for QoS but for NAT traversal, Firewall pin-hole requesting, etc.
• Resource reservation is increasingly seen as a network management issue. Some service providers will want to use contractual means for reserving bandwidth rather than protocol means.
37 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
NSIS Work Items
• Under review• Requirements of a QoS Solution for Mobile IP • Requirements for Signaling Protocols
• Being Discussed• Next Steps in Signaling: Framework• Security Threats for NSIS• RSVP Security Properties• Analysis of Existing Quality of Service Signaling Protocols
• Soon to be Submitted• NSIS Transport Layer Protocol (NTLP)• NSIS Applications (QoS; Middle Box traversal)
38 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
How
• Provide means for users to signal to edge network (end-to-edge).
• Allow for edge-to-edge signaling, however this may not be always needed.
• Application layer may wait until QoS requirements are fufilled before setting up sessions.
• Goals• Transparent - don’t require uses to know / set-up too much.• Simple – allow service provides to provision / allocate
resources as their business model calls for.• Extensible
39 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Possible Uses
• QoS• WLAN UNI for Requesting QoS into an IMS.• 3GPP2 QoS bearer• NNI protocol for GGSN-GGSN QoS reservations• Used with SIP QoS preconditions
• General• NAT Traversal• Firewall Traversal• Gateway Traversal
40 © NOKIA SIP&ALL-IP.PPT/ 29 April 2003 / John A. Loughney
Summary
• Integrating different access technologies (3G, WLAN, DSL, Dial-up):
• increases the potential for increasing subscribers.• increases accesses to services.
• Integrating/harmonizing signaling:• harmonizes network infrastructure.• simplifies network management.• simplifies charging/billing.• simplifies the user experience.