..
681.327.1 (0.75.8)
32.973.202 73
459
..
459 : . : - , 2011. 95 .
, , , , , , RTP , , , , .
681.327.1 (0.75.8)
32.973.202 73
-
,
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,
..
, 2011
. , 2011
1.
. : , . , , , , . , , , , , - . , . , .
1.1.
(Real-Time RT) (Non Real-Time NRT). (RT) , (, ) , . [1]. (Automatic Retransmission reQuest ARQ). TCP (Transport Control Protocol) TCP/IP. , NRT , . (Forward Error Correction FEC) , . UDP (User Datagram Protocol) TCP/IP. , , ( RT, NRT) UDP . [2] FEC UDP STARTAP.
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RT (Discrete media DM) (Continuous media CM), , .
. RT , , , . , , . , .
1.2.
. , , , FTP (File Transfer Protocol: ASCII ), HTTP (Hyper Text Transfer Protocol: HTML ) SMTP (Simple Mail Transfer Protocol: ). 7- US-ASCII, 8- ISO-8859, 16- Unicode 32- ISO 10646 , . , [3] 1.1.
. , , , TCP. UDP.
, , , . , , .
1.1
- | . |
-. | |
LZW | . . . |
Unix | LZW . 512 . |
1.3.
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|
, (sampling) (quantization). . . , 12 8 . 96 kbps 64 kbps. [4], 1.2, .
. 1-2 % . , , .
. , -, , . . , , (Real-Time Intolerant RTI). RTI 200 . , - (webcast), , . .
1.2
(Kbps) | ||
- (G.711) | (300 3300 Hz) | |
GSM | (300 3300 Hz) | |
CS-ACELP (G.729) | (300 3300 Hz) | |
G.723.3 | (300 3300 Hz) | 6.4 5.3 |
- (G.726) | (300 3300 Hz) | |
SBC (G.722) | (50 7000 Hz) | 48/56/64 |
MPEG layer III (MP3) | CD (10 22Khz) | 128 112 Kbps |
1.4.
, , flash-. , . , . , 4 6 480 640 24- . 56.6 Kbps . 10 , 100 14 . [5] 1.3. , [3]. , , . 5-10% , . : () , () , , () , .
1.3
Graphics Interchange Format (GIF) | 256 . LZW (Lempel-Ziv-Welch) . |
Portable Network Graphics (PNG) | . zlib, . . |
Joint Photographic Experts Group (JPEG) | - ( ). . . JPEG , (Progressive JPEG). Progressive JPEG . |
JPEG2000 | , . , (wavelet), , . . |
JPEG-LS | . LOCO-I (Low COmplexity LOssless COmpression for Images), HP. . |
Joint Bi-level Image Experts Group (JBIG) | - . . |
, . , .
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1.5.
, , 24 30 . , , . , , . . 1.4 [6] .
1.4
MPEG-I | VCR NTSC (352 x 240) CD-ROM (CD-I CD-Video ) 1.2 Mbps. |
MPEG-II | . . (DVB) High Definition Television (HDTV). MPEG-2 4 : (low) (352 x 240), (main) (720 x 480), -1440 (high-1440) (1440 x 1152), (high) (1920 x 1080). 3-100 Mbps. |
MPEG-IV | (64 Kbps). , . |
H.261 | ISDN , 64 Kbps. , . |
H.263 | (18-64 Kbps). |
.
1.6.
, . [7] . ( , ), (, , ). , TCP/IP. , , .
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1.6.1. ( )
1.1- 1.5, , , . , , . . - 200 . , .
1.6.2.
, , , . , UDP, . 1.5 .
: . , . . , . (, ).
1.5
( 3.4 ) | 8000 / | 96 Kbps | |
( 7 ) | 1600 / | 224 Kbps | |
( 20 ) | 44.1 K/ | 16 | 1.412 Mbps |
/ | |||
512 x 512 | 6.3 Mbps | ||
CCIR TV | 720 x 576 x 30 | 300 Mbps | |
HDTV | 1280 x 720 x 60 | 1.327 Gbps |
1.6.3.
, . . , , (error concealment techniques FEC), .
FEC . , FEC, . , , FEC . , , , . , FEC, , . FEC.
1.6.4.
. . , -. , .
, . , - , . , , - , . , .
|
|
:
. , (, ), , , IP .. , .
. . , , . .
. , (, ) (, ). , , . , , .
. , , . (timestamps) . , [8], .
. . : , , . , , . [9].
. , . . [11], , .
. . , IEEE 802.11x [12], . .
. , .
2.
, .
2.1.
, . . [12].
2.1.1.
, , . . . . [13].
2.1.2.
, . , :
. FIFO, , .
. . 10 Mbps Ethernet 100 Mbps fast Ethernet 10 .
Medium Access Control (MAC) . , (MAC protocol) [14]. MAC . , C bps, L , L/C. MAC TDMA (Time Division Multiple Access), , m , mL/C. Ethernet - [16]. Fast Ethernet , 10 Mbps Ethernet . Ethernet Ethernet , .
. . , . 10 Mbps LAN , . .
2.1.3.
. 200 . 20,000 , 0.1. . 200 , .
2.1.4.
, . , ( ). . , , . . . , . . . , ( ) . Integrated Services (Intserv) Multi-Protocol Label Switching (MPLS). , . Differentiated Services (Diffserv).
2.2.
(. 5). (best effort Internet model) . . , . . , TCP, (closed-loop feedback mechanism), TCP . . UDP, .
, (admission control), (bandwidth reservation) (traffic policing mechanisms). . , ( ) . .
2.3.
, , , , . , - , .
- . , . QoS , , . , .
2.4.
Integrated Services (Intserv), Differentiated Services (Diffserv) Multi-protocol Label Switching (MPLS) . , , , .
2.4.1.
. QoS , . , QoS : , .
, ( ) [15]. , QoS . , , , . , - . , .
, , [11]. . (jitter) (skew). , (. 2.1).
. 2.1. :
(a) ; (b) ; (c) .
. 2.1 (a) . . 2.1 (b) , . , . . .
. . 2,1 (). . .
. .
. , , , [8].
2.4.2.
( , , TCP), , . , .
(. . 2.2) QoS, ( QoS) , QoS [17]. , , .
. 2.2.
, QoS . , , , .
(measurement process module). , . . (bursty traffic), , , .
2.4.3.
, QoS , . , , . .
(Token Bucket ) [18]. : . (/c) . , .
, .
2.4.4.
, , , . , . , - , . . (ToS) IP. MPLS , IP.
2.4.5.
, FIFO, , , , .. . , . , . , .
2.4.6.
. , . , MPEG I, P B . I , I ( ). , , I, , , P B. , I. [19].
2.4.7. QoS
Open Shortest Path First (OSPF), Routing Information Protocol (RIP) Border Gateway Protocol (BGP) [20]. , ( ) , . , , . , , , , , .
QoS . , . 2.3 , X Y 4Mbps. , A-B-C ( ), , . A-E-D-C.
. 2.3. QoS
QoS, . [21] , , . , , QoS. [22] , QoS, . , QoS . .
2.5.
, Integrated Services Internet Engineering Task Force (IETF) (IntServ) [23]. . QoS, , . , , . , , , . , , , QoS.
Intserv . , , .
Intserv RTI, RTT . : (Guaranteed service), (Controlled Load service) (best-effort service). QoS [1]. : (filterspec) (flowspec). Filterspec , , . Flowspec (Tspec) (RSpec). Tspec (b,r), RSpec QoS , , .
, . (RSVP) [24]. . 2.4. PATH , . PATH . , PATH, RESV . RESV. , . , , .
. 2.4. RSVP
RSVP QoS. RSVP RSVP , . RSVP , . RSVP QoS, : QoS. , , . , IntServ.
2.5.1.
. , . , - , , , . , , .
(TSpec), , , , . , : 'B' , "R" , .
2.5.2.
RTT , , . , , .
, , . . , . , - .
TSpec. - , RSpec . , . .
2.5.3.
TSpec RSpec, . .
2.5.4. Intserv
Intserv RSVP, . , . , , . , RSVP . .
2.6.
(Differentiated Services Diffserv) Diffserv IETF , Intserv [25]. DiffServ , DS , . DS . , . DiffServ (Service Level Agreement's SLA) . SLA , ..
DS :
. DS. ( ) , ( ) () () DS. , , . DS. , , , DS. , QoS. , , DS , Behavior Aggregates Diffserv. 8- , (DS code-point). TOS IP- . (Traffic Conditioning Agreements TCA) DS , .
. DS DS. . , . Per-Hop Behaviors (PHB) .
, Intserv, , Diffserv .
2.6.1. Per Hop Behavior
PHB , , . PHB ( ), PHB, ( ). PHB . , . PHB . PHB . PHB 1 1 N 1. (Weighted Fair Queuing WFQ) (Random Early Detect RED). IETF PHB:
Assured Forwarding (AF) PHB. 4 . . .
Expedited Forwarding (EF) PHB. EF PHB , . , EF PHB, . , . EF PHB (Premium Service) . EF PHB . , EF PHB. EF PHB . , , .
2.7.
IP , (hop) (longest prefix match), .. IP- [26]. , . , . IP-, . ( ), . , . ATM , VPI/VCI . MPLS IP. , , IP.
, , .
Diffserv, MPLS , Label Edge Routers (LER), , Label Switching Routers (LSR). , MPLS, , . , . LSR MPLS Label Switched Path (LSP). , Diffserv, , .
MPLS Forward Equivalence Class (FEC) . , FEC. FEC . , FEC . . . LSP , LSP. :
Topology-driven label assignment. LSP ( FEC) LSR. LSR. LSP .
Request driven label assignment. LSP . RSVP. , LSP . , .
Traffic driven label assignment. . LSP , LSR . , .
MPLS , . FILO. . , , .
3. TCP/IP
, TCP/IP . (H.323 SIP), .
3.1.
[27]. , , IGMP (Internet Group Management Protocol). Ethernet, MAC-. , . , "flooding", "spanning tree", "reverse path broadcasting" "reverse path multicasting" . , Distance Vector Multicast Routing Protocol (DVMRP), Multicast extension to Open Shortest Path First (MOSPF), Protocol Independent Multicast (PIM) [28]. , , , .
MBone Multicast Backbone. Mbone , . MBone , . . IP-over-IP ( 4) .
ITU-T H.323 IETF Session Initiation Protocol (SIP), , Multi-point control unit, , / -. [29] QoS .
3.2.
, .
(Session Description Protocol SDP) [30] [31], IETF, ( , ). SDP . SDP , , , . attribute_type = . SDP . 3.1. , .
. 3.1: SDP
(Session Announcement). (Session Announcement Protocol SAP) [32][33] . SAP ( 9875). , . , , SAP, . , . SAP . SAP , .
(Session Identification). ( ) <Src Ip, Src Port, Dst IP, Dst Port, Protocol>. ,