Mastering SIP Advanced Duration: 5 days

Mastering SIP Advanced
CONTENT
Attending SIP Advanced (3 days) and SIP Troubleshooting (3 days) individually, with time in-between for practicing the knowledge learned, then refreshing and diving even deeper into the topic, is our recommended path to maximize the knowledge and skills needed for a SIP engineer. Becoming a good troubleshooter requires deep and thorough understanding of your subject, and allowing time for practical work between the courses allows for more in-depth understanding of the subject, and is highly recommended.

This course was mainly developed for customers where attending the individual courses; SIP Advanced (3 days) and SIP Troubleshooting (3 days), is not possible.
Is an extended version of our SIP Advanced course, but with additional time for exercises and with added theory and practical exercises focusing on troubleshooting SIP networks.
Functions such as proxy behavior, transaction, dialogs, DNS usage, B2B user-agents, different error situations, and a lot of other topics are covered in detail. You will learn how SIP works within IP-telephony as well as multimedia solutions such as Presence and Instant Messaging.
Theory chapters are interleaved with practical exercises to enhance the information from the presentation and to further improve the understanding of the protocols behavior.
This course will cover how SIP works both in wireline and wireless solutions.

TARGET AUDIENCE
The target group for this course is people that need to understand the SIP signaling protocol in detail. Among these people we will find testers, developers and implementers, or any VoIP engineer needing the ability to thoroughly analyze or troubleshoot a SIP network

PREREQUISITES
•    Good knowledge of data communication and TCP/IP.
•    Basic theoretical knowledge about SIP networks.
•    Basic familiarity with the Wireshark network analyzer is also recommended, since it will be used heavily during the course.
•    Practical/working experience with SIP networks is also highly recommended for the troubleshooting exercises.

NOTE: This course is not delivered with the FoldOut methodology.

Day 1

Designing a VoIP Protocol
•    Whiteboard discussion on the generic needs and features of a VoIP signaling protocol, and which choices were made when designing the SIP protocol.

The Basics

  • Background, history and Internet heritage
  • Main components; servers and clients.
  • Benefits and rules with different transport protocols
    • UDP, TCP, SCTP.
  • Basic sessions and SIP mobility features
    • Proxy and Redirect mode
    • SIP Methods & Response codes
    • SIP Registration
  • SDP Basics

Addressing and Registration     

  • Message structure and format rules.
    • Mandatory headers and parameters.
    • Addressing and using URIs
  • SIP Registration
    • Expiration and Deregistration
    • Registration rules
    • The location service

Exercise 1 – Registration and Basic Calls 

  • Registration issues
  • Basic SIP sessions with SIP proxy and location server
  • Using Wireshark for traffic monitoring
  • SIP Signaling and SDP Negotiation analysis
  • Methods; INVITE, BYE, REGISTER

Message Forwarding  

  • SIP message routing rules
    • Request-URI and Route headers
    • Via header response routing
  • Detailed proxy behavior
    • Location server lookup
    • Request forwarding
    • Response processing
    • Loop detection/prevention
  • Using DNS for inter-domain signaling
    • SIP related DNS records; NAPTR; SRV, A/AAAA
    • Load sharing and redundancy features

Session Management

  • Establishing sessions with INVITE
  • Using SDP for negotiation
    • SDP Offer/Answer Model
  • Dialog creation
    • Early Dialogs and UPDATE
  • Dialog state management
    • Route-set, Record-Routing, URI’s, and Dialog-ID.

Day 2

Exercise 2 – Call Signaling Details      

  • Inter-domain call setup and routing
  • DNS usage
  • RTP details
  • SIP Header analysis
  • Usage of Request-URI
  • Record-routing examples
  • ReINVITE’s or UPDATE for session re-negotiation

State handling

  • Statefullness in SIP Servers
    • Limitations of stateless servers
    • Transaction and dialog-stateful servers
    • Registration stateful servers.
  • The transaction layer
    • Client and server transaction state machines
    • The bugs and fixes for Non-INVITE transactions

Protocol extensions and updates

  • Extending the SIP protocol
    • Using OPTIONS
    • Negotiation and requiring extensions
    • Handling new SIP methods in old proxies
  • Reliable provisional responses
    • PRACK, RSeq and RAck
  • Forking and Cancelling requests
    • Cancel and stateful proxies
  • Caller preferences and Callee Capabilities
    • Addressing and Registration extensions
  • Using Early Media
    • Simplex or Full-duplex
    • Issues with forking.
  • Quality of Service and SIP/SDP

Exercise 3 – Forking and CANCEL

  • Forking Calls – When and Why?
  • Response processing at forking.
  • Method: CANCEL
  • Parallel and sequential forking.

Day 3

Security 

  • Firewalling SIP servers and clients.
  • Encryption and Authentication – How?
  • Firewalls and NAT/PAT-Firewalls and NAT/PAT
    • Session Traversal Utilities for NAT
    • Traversal Using Relays around NAT
    • SIP Outbound extension for NAT
    • Symmetric Responses and Connection reuse.
    • Global Routable User agent URI, GRUU
  • SIP Privacy and Authenticity
    • S/MIME examples for end to end security
    • Privacy and Anonymity
  • Securing the media channel
    • Secure RTP with ZRTP or MIKEY

Services and Applications  

  • Service creation possibilities with SIP
    • Overview of SIP-CGI, CPL, Java servlets, Jain, OSA/Parlay.
    • Service examples with CPL
  • SIP Basic call-services and PBX-like features.
    • Call-forwarding, voicemail, CLIR/CLIP, etc
  • Call-transfer and Call-Pickup
    • REFER and Replaces:
  • 3rd party call control
  • SIP for events
    • The presence architecture
    • Triggering presence
    • Dialog issues
  • Instant messaging in SIP
    • Stand-alone messages with MESSAGE
    • Session based messaging with MSRP
  • B2BUA (Back to back User Agent)
    • Requirements and Possibilities

Exercise 4 – Services   

  • Presence
  • Instant messaging
  • Methods; SUBSCRIBE, NOTIFY, PUBLISH, MESSAGE

Classic Telephony Using SIP    

  • Sending DTMF in VoIP
    • DTMF and RTP, rfc2833/4733
    • INFO and SUBSRIBE/NOTIFY
  • Merging PSTN Networks and SIP
    • SIP for telephones – SIP-T
    • Q.1912.5– SIP-I
  • E.164 Phone numbers and SIP-addresses
    • Tel: and SIP: URIs
    • Address translation, interworking.
    • DNS and ENUM.
  • Mobile SIP Telephony
    • IMS, IP Multimedia Subsystem

Exercise 5 – Security and DNS     

  • User authentication/authorization and http digest
  • Understanding DNS queries

Day 4
Repetition of the previous three days
Troubleshooting Basics

  • Troubleshooting techniques
    • Generating baselines
    • Documenting the system
    • Reference Models
    • Isolating the error

Troubleshooting Tools

  • Overview of useful troubleshooting tools
    • Wireshark, Tcpdump
    • SipSAK, SIPp, SIP Scenario Generator
    • DNS, dig and nslookup.
  • Practical Exercises

SIP Troubleshooting

  • Finding the rules
    • IETF tools, IETF Workgroups
    • SIP Signaling Checklist
  • Important SIP Rules
    • Invite vs Non Invite
    • SDP Usage
    • State handling
    • Message Parsing
    • Registration and Caller preferences
  • Practical Exercises

Day 5

Dialog Management

  • Rules for Dialog state management
    • Creating, modifying, releasing
    • Recording Routes and Route-set management
    • Early dialogs, Early media, and PRACK.
  • Practical Exercises

Message Forwarding

  • More routing and Record-Route
  • Loops, Forking, and CANCEL
  • Transactions and the state machines
    • Updates to the state machines, rfc4320/21
    • SIP Timers
  • Practical Exercises

DNS and Transport

  • The rules for selecting transport protocol
    •  Message sizes, URI analysis, and DNS
  • Details of the DNS selection process
  • Signaling redundancy and failures
  • ENUM, E.164 and Telephone numbers.
  • Practical Exercise

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