Future Signaling Protocols What’s New in IETF

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

[email protected]


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


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


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)


SIGTRAN Network


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.


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


Communication Within IP Networks

SP

UA

SCTP

IP

SEP

SP

UA

SCTP

IP

SEP

Telephony signaling over IP

IPSP: IP Signaling Point.


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)


Network View


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.


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


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)


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.


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.


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


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.


Part 2

• Diameter / AAA (Authentication, Authorization & Accounting)

• SeaMoby (Seamless Mobility)

• NSIS (Next Steps in Signaling)


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


Standard RADIUS Model


Diameter Roaming


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.


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.


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


Diameter Proxy Example

NetworkAccess Server

Primary Proxy Server

Backup Proxy Server

Primary Home Server

Backup Home Server

local service provider

home service provider


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


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


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.


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.


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


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?


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


Context Transfer Framework

New RouterPrevious Router

CT Request

Public internet

CT Ack

Home Agent Correspondent

node


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.


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.)


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.


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)


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


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


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.