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Published in authors version

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681.327.1 (0.75.8)

32.973.202 73

459

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459 : . : - , 2011. 95 .

 

, , , , , , RTP , , , , .

681.327.1 (0.75.8)

32.973.202 73

-

 

,

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,

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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.

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.

, (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) - . .

, . , .

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. , , .

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>. ,



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