RSVP Myungchul Kim

From Ch 12 of book “ IPng and the TCP/IP protocols ” by Stephen A. Thomas, 1996, John Wiley & Sons. Resource Reservation Protocol (RSVP) RSVP operation –Flows RSVP identifies a flows by its destination IP address and a source IP address. RSVP does not understand the flowspec. RSVP supports both unicast and multicast flows.

–Reservation receiver-initiated reservations. easily support a dynamic environment: join, drop out. how does a receiver know to make a reservation in the first place?

–Path messages make sure that resources are reserved along the correct path. generated by a flow ’ s sender. travel in the same direction as the flow itself. at each hop, the router inserts its own IP address as the message ’ s last hop.

–Merging reservation requests

–Reservation styles shared explicit reservation: an application must explicitly identify every participating sender. wildcard filter: an application shares a resource without identifying every sender.

–RSVP and dynamic networks a soft state because both its paths and its reservations are always considered tentative.

–RSVP message formats in the payload of IP datagrams type: Table 12.2 fragmentation: message ID, fragment offset and more fragments bits.

RSVP and INTSERV –RSVP: a signaling protocol, configure traffic handling mechanisms in network devices. –Integrated Services: a framework for providing end-to-end services in the context of RSVP –Integrated Services over Specific Link Layers (issll) : define the underlying traffic handling mechanisms that would offer QoS support on different media.

–problems of RSVP and INTSERV RSVP were available only on certain UNIX. implemented on every network devices -> not scalable no policy mechanisms in a secure manner. not on the non-multimedia mission-critical applications. –valuable components because RSVP in Windows 2000 scalability <- disassociating RSVP from per- flow traffic handling policy component non-multimedia applications

VoIP (SIP, H.323) Myungchul Kim

By H.Schulzrinne, August 12, 20001

The Session Initiation Protocol: Internet- Centric Signaling –Henning Schulzrinne and Jonathan Rosenberg, The Session Initiation Protocols, IEEE Comm., pp , Oct –SIP Signaling protocol: RFC 2543 (March 1999) Initiates, modifies, and terminates network sessions Services such as VoIP including instant messaging, event notification, distributed games Does not reserve resources or establish circuits in the network RTP, RTSP(streaming), Media Gateway Control Protocol, Megaco (H.248), Session Description Protocol, Session Announcement Protocol, Telephony Routing over IP (TRIP) Anything addressable by a host name can participate in a SIP session Discovery of a user: personal mobility Could be though of as an application-layer anycast Ability to have users and administrators program services

–Architecture: user agent, registrars, proxy, and redirect servers. –Signaling URI Figure (next slide) The path of the signaling messages may be completely different from that of the media exchanged between caller and callee. UDP –SDP: a description format (what media streams it wants to receive and its receive capabilities) –SIP message format: textual encoding 838 – 1240 bytes of SIP messages to set up a call (800 bytes for H.323) –Forking A server can send out two or more requests to different destination Call forwarding to voice mail, automatic call distribution, and user location

–Reliability UDP Clients retransmit INVITE requests until a provisional response arrives, and servers retransmit responses until confirmed by an ACK request. –Security SIP inherits the basic and digest authentication mechanisms from HTTP –Expressing Caller Preferences Users register their terminal characteristics with the local proxy Page 138, middle of the right column

–Quality of Service Using SIP to directly set up resource reservations is not appropriate SIP can be used to negotiate the use of QoS mechanisms COMET

–Mobility Precall terminal mobility Mid-call mobility –SIP and MGCP/MEGACO

VoIP over IP Signaling: H.323 and Beyond –Hong Liu and Petros Mouchtaris, Voice over IP Signaling, pp , Oct –Introduction Precommercial ( ), PC-centric ( ), and carrier grade (1998 on) Previous limitation –A gateway handles signaling conversion, call control, and media transcoding –No provision for SS& connectivity –Call control: media gateway controller –Media transformation: media gateway –Media Gateway Control Protocol (MGCP) –H.248 or Megaco, in June 2000

–H.323 Overview Architecture –Terminal –Gatekeeper: address translation, access control, bandwidth management, and locating GW –Gateway –Multipoint control unit: multipoint conference

Signaling and control –Registration Admission and Status (RAS) –Q.931 –H.245: for connection control to negotiate media processing control and used to exchange terminal capability –RTP

–H.323 Interworking with the PSTN H.323 TE to phone; phone to H.323 TE; and phone to phone via intermediate H.323 networks GW –PSTN interface –VoIP interface –Signaling conversion –Media transformation –Connection management

Limitations of H.323 –Scalability: a few thousand –ISDN trunks instead of SS7 connectivity –Availability: no mechanism for failover –User friendliness: two-stage dialing Separating the signaling and media transformation functions would allow for more scalable GWs. Functional decomposition of H.323 GW

Improvement of H.323 –Scalability –SS7 connectivity –Availability –One-stage dialing –H.323 and SIP SIP is much more light weight Call agents or soft switches that support H.323, SIP and MGCP.