VOIP & MOBILE IP
PREVIOUS LECTURE Why Networks? And types of Networks Network Topologies Protocols, Elements and Applications of Protocols TCP/IP and OSI Model Packet and Circuit Switching 2
TODAY AGENDA VOIP Mobile IP 3
VOICE OVER IP (VOIP)
WHAT S VOIP? VoIP is the ability to make telephone calls and send faxes over IP-based data networks with a suitable quality of service and superior cost/benefit.
MOTIVATIONS FOR VOIP Demand for Multimedia communication Demand for integration of Voice and Data networks Cost Reduction in long distance telephone calls
HOW TO VOIP? Analog Digital Voice Compression to less than 32Kbps Transfers through Routers, LAN Switches etc, using their Protocols
VOICE TO/FROM IP Analog Voic e CODEC: Analog to Digital Compress Create Voice Datagram Add Header (RTP, UDP, IP, etc) Digital Network
VOICE TO/FROM IP Digital Network Process Header Re-sequence and Buffer Delay Decompress CODEC: Digital to Analog Analog Voice
CONFIGURATION OPTIONS Telephone-to-Telephone
PC-TO-PC
TELEPHONE-TO-PC
MAIN ISSUES Quality of Voice Interoperability Security Integration with Public Switched Telephone Network(PSTN) Scalability
VOIP STANDARDS ITU H.323 IETF Session Initiation Protocol (SIP) Media Gateway Control (Megaco) Signal Transport (SigTran)
ISO REFERENCE MODEL AND VOIP STANDARDS ISO Protocol layer Protocols and standards Presentation Codecs / Applications Session H.323 / SIP / MGCP Transport Network Link RTP / TCP / UDP IP FR, ATM, Ethernet, PPP, HDLC, etc.
H.323 ENTITIES Terminals Gateways Gatekeepers Multi-point Control Units (MCU)
TERMINAL Endpoint on a LAN Supports real-time, 2-way communications with another H.323 entity Must support: Voice - audio codecs Signaling and setup Optional support: Video Data
GATEWAY Interface between the LAN and the circuit switched network Translates communication procedures and formats between networks Call setup and clearing Compression and packetization of voice Example: IP/PSTN gateway
GATEKEEPER Optional (e.g., Netmeeting does not use gatekeepers), but must perform certain functions if present Manage a zone (a collection of H.323 devices) Usually one gatekeeper per zone; alternate gatekeeper might exist for backup and load balancing Typically a software application, implemented on a PC, but can be integrated in a gateway or terminal
MULTI-POINT CONTROL UNIT (MCU) Endpoint that supports conferences between 3 or more endpoints Can be stand-alone device (e.g., PC) or integrated into a gateway, gatekeeper or terminal Typically consists of multi-point controller (MC) and multi-point processor (MP) MC - handles control and signaling for conference support MP - receives streams from endpoints, processes them, and returns them to the endpoints in the conference
Transfer H.323 of PROTOCOL STACK real-time media (audio and video) Registration Control and Signaling
VoIP Origination side Analog voice is sent from telephone set to local office. Local switch converts analog signal to PCM and transmits 64kbps bit stream to the gateway. Gateway receives 64kbps bit stream and does the following Compress speech Convert speech samples to datagrams Transmit speech datagram over IP network VoIP Termination side VoIP gateway receives speech datagrams Convert Speech datagram to PCM speech. Transmit 64Kbps PCM speech to Local switch Local switch converts PCM to analog voice and sends it to telephone set
H.323 CALL STAGES Discovery and Registration(RAS) Who am I Call Setup(RAS/H.225/Q.931) Whom I want to call Call Negotiation (H.245) These are our capabilities Media Channel Setup(H.245) Let s open audio channel Media Transport( RTP/RTCP) Send audio datagrams Call termination (H.245/H.225/RAS) We are
Caller Number : 785-537-2736 Called Number : 410-944-511 ITSP Number : 1-888-745-2654 Simple VoIP Call Local Loop Trunk Gateway 785-537- 2736 Local Switch 1-888-745-2654 Caller dials ITSP toll free number : 1-888-745-2654 Caller gets connected to VoIP gateway of ITSP
Simple VoIP Call Gatekeeper Gateway LRQ LCF AR QACF 785-537- 2736 Local Switch 1-888-745-2654 What is the IP address of the destination gateway for 410-944-2511?-LRQ The IP address of the destination gateway is 154.23.78.345. LCF May I call the IP address? ARQ You may use XX Kbps bandwidth - ACF
Simple VoIP Call Gatekeeper Gateway Connect H.225/Q.931/H.245 785-537- 2736 Local Switch The setup message consists of Originator gateway IP address (129.130.10.123) (154.23.78.345) 1-888-745-2654 Destination Gateway IP address Caller-number (785-537-2736) Called-number (410-944-2511) H.245 request: OpenLogicalChannelForAudio Destination Gateway
Simple VoIP Call Gatekeeper Gateway ACF 785-537- 2736 Local Switch 1-888-745-2654 Destination gateway makes a request to the gatekeeper to accept the call from the originator May I call the originator gateway IP address? ARQ Yes,You may use XX Kbps bandwidth - ACF AR Q Destination Gateway
Simple VoIP Call Gatekeeper Gateway Connect H.225/Q.931/H.245 785-537- 2736 Local Switch 1-888-745-2654 Destination Gateway Destination gateway sends a connect confirm message.
Simple VoIP Call Gatekeeper Local Switch Gateway Gateway Local Switch Destination Gateway establishes PSTN connection with PSTN circuit switch and H.245 audio channel Caller will hear the ringer tone generated by the destination switch
SIP: SESSION INITIATION PROTOCOL IETF s Signaling Protocol for real time calls and confernces over IP networks. Integrated heavily w/ Internet technologies such as web (http), email & messaging services, and directory services (LDAP, DNS) Location Independent and hence opted for Mobile Networks SIP is complimentary to MGCP SIP Provides Session Control SGCP/MGCP Provides Device Control
SIP ARCHITECTURE Client/Server in Nature Major Entities User Agent Proxy Server Redirect Server SIP Registrar
SIP ENTITIES User Agents User Agent Client (UAC) User Agent Server (UAS) Network Servers
SIP PROXY OPERATION 2. When user picks up phone and dials destination phone number or URL, request is sent to the proxy server SIP Proxy Server 3. Proxy server looks up phone number or URL to registered called party, SIP server then sends invitation to called party 4. Called Client is informed of incoming call by an invitation from proxy server SIP Client Caller SIP Client Callee 5. SIP Clients open RTP session between themselves when the called user picks up the phone 1. SIP Clients registers with SIP servers at login or at boot up
SIP REDIRECT OPERATION 2. When user picks up phone and dials destination phone number or URL, request is sent to the redirect server SIP Redirect server 4. Call originator sends invitation to destination 3. Redirect server looks up phone number or URL to registered called party, SIP server then sends the address back to the call originator 5. Called client is informed of incomi call by invitation message (Phone rin SIP Client Caller SIP Client Callee 6.SIP Clients open RTP session between themselves when the called user picks up the phone 1. SIP Clients registers with SIP servers at login or at boot up
H.323 VS SIP H.323 SIP Philosophy Reliability Message Encoding Addressing Architecture Designed for multimedia communication over different types of networks Designed to handle failure of network entities Encodes in compact binary format Flexible addressing scheme using URLs and E.164 numbers Monolithic Designed to session b/w two points No defined procedures for handling device failure Encodes in ASCII text format. Hence easy to debug and process Understands only URLs style addresses Modular
QOS ISSUES Delay Jitter Packet Loss Re-ordering One way latency for high quality voice must not be greater than 150ms. Delay greater than 50ms leads to echo and talker overlap. Variation in inter-packet arrival time. The solution to this problem is to introduce jitter buffers. Loss in excess of 5-10% causes significant degradation in voice quality. Packets may arrive out of order and this leads to garbled speech.
BILLING ISSUES Time-based Metered by flow duration, time-ofday, time-of-week Destination, distance, carrier-based QoS based Rated by called and calling station ids associated with the sequence of stages used to support the call Rated by established service parameters such as priority, selected QoS and latency.
OSP WAY OF BILLING
COST CONSIDERATIONS Cisco 1750 Modular Access Router Ericsson WebSwitch 100 Phone Gateway P4 Multi- Tech Multi VOIP MVP400 Nortel Passport 4430 Multi service Access Switch Price $2,695 $1,091 $2,999 $3,200 Product type Router Gateway Gateway Router Phone ports Up to 6 4 4 Up to 6 H.323 support Yes Optional (with external gateway) Yes No
REFERENCES http://www.protocols.com/papers/voip.htm http://www.networkmagazine.com/encyclopedia/search?te rm=iptelephony ftp://ftp.netlab.ohio-state.edu/pub/jain/courses/cis788-99/voip_protocols/index.html http://members.tripod.com/taegon/voip/current_problems.ht m http://www.itpapers.com/techguide/voiceip.pdf http://www.zdnet.com/products/stories/reviews/0,4161,26267 92,00.html
MOBILE IP
TRULY MOBILE NETWORKING Provide confident access to the Internet anytime, anywhere Reconnection occurs automatically and noninteractively Mobility transparent to applications and higher level protocols such as TCP
TODAY S INTERNET PROTOCOL Packets are routed to destinations based on IP address
APPLY TO MOBILE NETWORKING
APPLY TO MOBILE NETWORKING X 128.143.77.84
MOBILE IP APPROACH Mobile IP uses two IP addresses: Home address: The IP address assigned to the mobile node, making it logically appear attached to its home network. Care-of address: An IP address at the mobile node's current point of attachment to the Internet, when the mobile node is not attached to the home network.
MOBILE NETWORK TERMINOLOGY (1) Home network: The network at which the mobile node seems reachable, to the rest of the Internet, by virtue of its assigned IP address. Foreign network: The network to which the mobile node is attached when it is not attached to its home network, and on which the care-of address is reachable from the rest of the Internet.
MOBILE NETWORK TERMINOLOGY (2) Home agent: A router on the home network that effectively causes the mobile node to be reachable at its home address even when the mobile node is not attached to its home network. Foreign agent: A router on the foreign network that can assist the mobile node in receiving datagrams delivered to the care-of address.
HOW MOBILE IP WORKS 128.143.77.84 HA
HOW MOBILE IP WORKS Discovering the care-of address Registering the care-of address Tunneling to the care-of address HA Register FA Discovery 128.143.77.84
AGENT DISCOVERY PROTOCOL Extends ICMP Router Discovery protocol ICMP Router Discovery Protocol enables hosts attached to multicast or broadcast networks to discover the IP addresses of their neighboring routers. Agent advertisements: The mobile agent broadcast agent advertisements at regular intervals. Agent solicitation: The mobile node broadcast or multicast a solicitation that will be answered by any foreign agent or home agent that receives it.
ADVERTISEMENT MESSAGE FORMATS ICMP Router Advertisement Agent Advertisement extension Type: 16 R: register required B: busy H: home agent F: foreign agent M: minimum encapsulation G: GRE encapsulation V: Van Jacobson header compression
ADVERTISEMENT MESSAGE FORMATS ICMP Router Advertisement Prefix Length extension Type: 19 Prefix Length:network number of the corresponding Router Address listed in the ICMP Router Advertisement portion of the message.
MOBILE NODE MOVE DETECTION Lifetime based The mobile node record the Lifetime of advertisement message. If it fails to receive another advertisement from the same agent until the the Lifetime expires, it considers to find a new agent. Network prefixes based The Prefix-length extension is used to determine if the newly received advertisement is in the same subnet as the mobile node s current care-ofaddress.
REGISTRATION Exchange of Registration Request and Registration Reply messages: UDP using well-known port 434 MH: mobile host; FA: Foreign Agent; HA: Home Address
FOREIGN AGENT CONSIDERATION Each foreign agent must be configured with a care of address For each pending or current registration, the foreign agent maintains a visitor list entry containing: Link-layer source address of the mobile node The mobile node s Home Address The Home Agent address The identification field The requested registration Lifetime The remaining Lifetime of the pending or current registration
SECURITY CONSIDERATIONS IN REGISTRATION Danger: Registration Request works remotely to the home agent to affect the home agent's routing table Security: Authentication: Home agents and mobile nodes perform authentication using MD5 algorithm and key size of 128 bits. Replay Protection: The Identification field is used to verify that a registration message has been freshly generated. timestamp, random number
PROBLEMS FACING MOBILE IP Security issues Routing inefficiency Triangle routing Ingress filtering User perceptions of reliability Competition from other protocols
REFERENCE "Mobile Networking through Mobile IP," C. Perkins, IEEE Internet Computing, Vol. 2, No. 1, 1998. "Mobile IP," C. Perkins, IEEE Communications Magazine, Vol. 35, No. 5, 1997.
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