Computer Networking From LANs to WANs: Hardware, Software, and Security Chapter 14 Multimedia Networking

Computer Networking From LANs to WANs: Hardware, Software, and Security2 Objectives Explain the basic properties of GIF, JPG, and PNG image files Discuss the various sound file formats, such as WAV, MID, and MP3 Describe MPEG, Voice-over-IP, and multicasting

Computer Networking From LANs to WANs: Hardware, Software, and Security3 Image Files Web browser image types –Graphics Interchange Format (GIF) –Joint Photographic Experts Group (JPEG) –Portable Network Graphics (PNG) Image file types and their properties –Affect Web page application development and performance

Computer Networking From LANs to WANs: Hardware, Software, and Security4 GIF images 256 colors possible (maximum) –Eight bits needed to store pixel color –Not photographic quality –Suitable for buttons, banner ads, or other Web page graphics Lossless compression –Uses LZW (Lempel-Ziv-Welch) algorithm No original image data lost during compression

Computer Networking From LANs to WANs: Hardware, Software, and Security5 GIF Images (cont’d.) Animation and transparency support built-in –Animation images stored in a single GIF image file –Appropriate time delays inserted between each stored image display Transparency –Accomplished by assigning one of the 256 color values to be the transparent color

Computer Networking From LANs to WANs: Hardware, Software, and Security6 JPG Images 24-bit color (16,777,216 colors possible) –Provides high quality photographic-quality color Lossy compression –Using the DCT (Discrete Cosine Transform) algorithm on 8-by-8 blocks of pixels –Superior to lossless GIF compression No animation or transparency features available

Computer Networking From LANs to WANs: Hardware, Software, and Security7 Figure 14-1 Sample image and the effect of compression on text Table 14-1 Comparing EARTH.JPG and EARTH.GIF files

Computer Networking From LANs to WANs: Hardware, Software, and Security8 PNG Images PNG-8: –Supports 8-bit color palette (256 colors), 1-bit transparency –Better compression than equivalent GIF image PNG-24 –Supports 24-bit color palette (16 M colors) –Similar to JPG image except lossless compression method used Animation –Provided by the Multiple-image Network Graphic (MNG) image format

Computer Networking From LANs to WANs: Hardware, Software, and Security9 PNG Images (cont’d.) Pixel transparency –Value between 0 (full transparency) and 255 (no transparency –Called alpha channels –More realistic blending of images with backgrounds

Computer Networking From LANs to WANs: Hardware, Software, and Security10 Sound Files Three types of sound files are popular on the Web –WAV files –MID –MP3

Computer Networking From LANs to WANs: Hardware, Software, and Security11 WAV Files Standard Windows audio file format Figure 14-2(a) Windows XP Sound Recorder displaying a portion of BLAST.WAV Figure 14-2(b) Windows Vista Sound Recorder ready to record

Computer Networking From LANs to WANs: Hardware, Software, and Security12 WAV Files (cont’d.) Figure 14-4 Changing the sampling properties Figure 14-3 BLAST.WAV properties

Computer Networking From LANs to WANs: Hardware, Software, and Security13 MID Files File extension –Used on Musical Instrument Digital Interface (MIDI) files Contains information (MIDI sequencer commands) –What notes to play, how to play them 128 pitched instruments can generate 24 notes in 16 channels –PC sound card uses MIDI information to reproduce notes Produces very complex sounds –With small amount of data

Computer Networking From LANs to WANs: Hardware, Software, and Security14 MP3 Files MPEG Audio Layer 3 files Moving Picture Experts Group (MPEG) audio, video –Encoding methods for creating high quality, low-bit rate multimedia files –Three audio layers Use perceptual audio coding and psychoacoustic compression for encoding audio, compressing data Table 14-2 MPEG audio layer differences

Computer Networking From LANs to WANs: Hardware, Software, and Security15 MP3 Files (cont’d.) Benefit: smaller file size, identical sound quality Used to burn audio CD-ROM Downloadable into a portable MP3 player Table 14-3 Comparing WAV and MP3 file sizes

Computer Networking From LANs to WANs: Hardware, Software, and Security16 The Digital Conversation Figure 14-5 Analog and Digital conversions

Computer Networking From LANs to WANs: Hardware, Software, and Security17 Transmitting Data over a Network Network overhead –26 bytes of Ethernet framing –24 bytes of IP header –24 bytes of TCP header Figure 14-6 Network overhead in an Ethernet frame

Computer Networking From LANs to WANs: Hardware, Software, and Security18 Transmitting Data over a Network (cont’d.) Network overhead (cont’d.) –Affects bandwidth requirements –74 bytes of overhead 5.28% of a 1400 data byte message 92.5% of a 80-byte data message

Computer Networking From LANs to WANs: Hardware, Software, and Security19 Transmitting Data over a Network (cont’d.) Table 14-4 Transmitting 8000 bytes (64,000 bits) of data using multiple packets

Computer Networking From LANs to WANs: Hardware, Software, and Security20 Voice-over-IP Method for sending voice and fax data –Uses the IP protocol Interfaces with the public switched telephone network (PSTN) –Attempts to provide same service quality Several different IP protocols used –Real-Time Transfer Protocol (RTP) –Real-Time Control Protocol (RTCP) –Resource Reservation Protocol (RSVP)

Computer Networking From LANs to WANs: Hardware, Software, and Security21 Figure 14-7 VoIP architecture

Computer Networking From LANs to WANs: Hardware, Software, and Security22 Voice-over-IP (cont’d.) H.323 standard –Specifies voice processing, gateway/terminal operation Factors impacting conversations –End-to-end delay –Jitter –Packet loss –Out-of-order arrivals

Computer Networking From LANs to WANs: Hardware, Software, and Security23 Voice-over-IP (cont’d.) Standards exist for rating VoIP conversation quality Lacks security –Can extract entire conversation from packet capture Table 14-5 Voice Quality Test Scores

Computer Networking From LANs to WANs: Hardware, Software, and Security24 Voice-over-IP (cont’d.) VoIP services becoming more common –Residential, business communities VoIP service providers –Offer all traditional phone company features Many VoIP network devices on the market today Figure 14-10(a) Linksys PAP2 indicator lights

Computer Networking From LANs to WANs: Hardware, Software, and Security25 Video Great bandwidth required User can easily spot problems with video stream Real-time video requirements –Powerful processor, fast network connection Protocols used to manage information stream –RTP, RTCP, RSVP Video cameras now affordable for PCs

Computer Networking From LANs to WANs: Hardware, Software, and Security26 MPEG Files Defines set of digital video parameters –Bit rate, resolution, compression techniques Video compression: lossy –Uses Discrete Cosine Transform Three frame types: –I (Intra): stand-alone video frame –P (Predicted): generated using most recent I or P frame –B (Bidirectional): generated based on past, future frames

Multicasting Eliminates large portion of duplicated information –Server sends one copy of video data to a multicasting-enabled switch –Switch forwards single copy to other multicasting- enabled switches They replicate video data, forward copies to each client IP multicasting –Uses Internet Group Management Protocol (IGMP) MBone –Experimental multicasting backbone Supports multicasting over the Internet Computer Networking From LANs to WANs: Hardware, Software, and Security27

Computer Networking From LANs to WANs: Hardware, Software, and Security28 Figure Unicasting versus multicasting

Computer Networking From LANs to WANs: Hardware, Software, and Security29 Games Network computer games growing in popularity One machine runs game in server mode –Multiple game client machines connect to it Factors developers consider for real-time environments –Available bandwidth, communication delay, processing speed Packet problems affect game play –Dead reckoning Combats effect of packet loss on player position

Computer Networking From LANs to WANs: Hardware, Software, and Security30 Troubleshooting Techniques Bandwidth issues –Streaming music and video are high bandwidth applications CODEC issues –Video file must be played with the same CODEC used to create the video file Quality of Service –Affects users ability to use audio, video, VoIP phone services May be necessary to prioritize network traffic

Computer Networking From LANs to WANs: Hardware, Software, and Security31 Summary Web browsers accept –GIF, JPG (or JPEG) or PNG images Audio file types –Wave, MIDI, MP3 Streaming media describes any media type (audio, video, animations,etc.) that may be streamed Voice-over-IP (VoIP) –Method for sending voice and fax data using IP