MOHAMED EL-SHAER Teaching Assistant. Room TASK Exercises Thu., Nov. 17, 2014 CONTENT

Transcription

1 Room C3.221 Tel : , ext Fax : Mail: robil.daher@guc.edu.eg; robil.daher@ieee.org Room mohamed.el-shaer@guc.edu.eg Faculty of Information Engineering and Technology (IET) German University in Cairo COURSE SIGNALING AND NETWORK CONTROL (SNC) NETW th Semester WS 2014 TASK Exercises Thu., Nov. 17, 2014 FOCUS SESSION INITIATION PROTOCOL (SIP) CONTENT I SIP Telephony System Deployment... 2 II SIP Signaling... 3 II.1 Session Setup/Termination Warm-up... 3 II.2 Session Setup/Termination Multi-Proxies... 3 II.3 Session Setup/Termination Different Domains... 4 II.4 Session Signaling Analysis... 4 Exercises NETW-704 S&NC 1/5

2 I SIP TELEPHONY SYSTEM DEPLOYMENT The small company ComSIP plans to replace its old telephone system with an SIP -based telephone system. You as a consultant is asked to design this system for the company under considering the following points: o Number of users: 25 o Network architecture is available; DHCP is used, but no DNS o Preferred number of SIP Phones (desktop): 20 o Consider the connection with a global SIP service provider o Consider serving the PSTN connections via an external service provider o Consider at least the services: voice/video calling, instant messaging and presence service Accordingly, you are asked to make several decisions: 1. What hardware and software components are required for which SIP components? 2. What SIP servers should be integrated,.e.g. redirect server or proxy (stateless or stateful), etc.? 3. What configuration could be required, e.g., SIP naming/numbering scheme, IP related configuration, etc.? 4. What recommendations from your perspective would you give for points/issues, which are not covered by the request of the company? Please if you believe that you still need more information to be able to finalize your design, then cover this lack of information by providing your own assumptions. Exercises NETW-704 S&NC 2/5

3 II SIP SIGNALING II.1 Session Setup/Termination Warm-up Alice and Bob work in the same company ComSIP but in different departments. Alice calls Bob at 10:00AM to inform him about the next meeting. If you know that o Alice and Bob have the SIP-addresses alice@comsip.com and bob@comsip.com, o only single proxy server (sipproxy@comsip.com) is used into the company, 1. Draw the signaling sequence between Alice and Bob during the whole session! 2. Does the signaling scheme will be changed if using dialog stateful proxy? If yes, 3. Let RTT denotes the Round-Trip Time between an UA/Server and Server/UA. II.2 Session Setup/Termination Multi-Proxies Alice and Bob work in the same company ComSIP but in different departments. Alice calls Bob at 10:00AM to inform him about the next meeting. If you know that o Alice and Bob have the SIP-addresses alice@comsip.com and bob@comsip.com, o A proxy server is used for each department into the company: sipproxy_a@comsip.com and sipproxy_b@comsip.com for departments of Alice and Bob, o Each proxy server acts as proxy and registrar server 1. Draw the signaling sequence between Alice and Bob during the whole session! 2. Does the signaling scheme will be changed if using dialog stateful proxies? If yes, 3. Let RTT denotes the Round-Trip Time between an UA/Server and Server/UA. Exercises NETW-704 S&NC 3/5

4 II.3 Session Setup/Termination Different Domains Alice works in the company ComSIP and wants to call her customer Cesar who works in another company TelSIP. Alice calls Cesar at 10:00AM to inform him about the next meeting. If you know that o Alice and Cesar have the SIP-addresses alice@comsip.com and cesar@telsip.com, o A proxy server is used for each company: compro@comsip.com and telpro@telsip.com companies ComSIP and TelSIP, o Each proxy server acts as proxy and registrar server 1. Which entities would be included into the session initiation process and why? 2. Draw the signaling sequence between Alice and Cesar during the whole session! 3. Does the signaling scheme will be changed if using dialog stateful proxies? If yes, 4. Let RTT denotes the Round-Trip Time between an UA/Server and Server/UA. II.4 Session Signaling Analysis The following figure shows the signaling between Alice ( ) and Bob ( ); Alice and Bob belong to different domain, as you can deduce from the figure. If you know that the header of message (1) in Figure 2 might look like the following: INVITE sip:bob@biloxi.com SIP/2.0 Via: SIP/2.0/UDP :5060 Max-Forwards: 70 To: Bob <sip:bob@biloxi.com From: Alice <sip:alice@atlanta.com;tag= Call-ID: a84b4c76e66710@ CSeq: INVITE Contact: <sip:alice@atlanta.com> Content-Type: application/sdp Content-Length: 142 And the header of message (13) in Figure 2 might look like the following: SIP/ OK Via: SIP/2.0/UDP server10.biloxi.com Via: SIP/2.0/UDP bigbox3.site3.atlanta.com Via: SIP/2.0/UDP :5060 To: Bob <sip:bob@biloxi.com;tag=a6c85cf From: Alice <sip:alice@atlanta.com;tag= Call-ID: a84b4c76e66710@ CSeq: INVITE Contact: <sip:bob@biloxi.com> Exercises NETW-704 S&NC 4/5

5 Content-Type: application/sdp Content-Length: 131 Answer the following questions: 1. Why the message (13) has 3 times via-fields in its header? 2. Why the fields Call-ID and Cseq are the same in both messages? 3. Is there a message body? If not, why? If yes, how long and which protocol? 4. How may message (16) looks like? Exercises NETW-704 S&NC 5/5