Khi ch\u1ecdn mua m\u00f4\u0111em, ch\u00fang ta s\u1ebd ch\u00fa \u00fd t\u1edbi m\u1ed9t ch\u1ec9 ti\u00eau r\u1ea5t quan tr\u1ecdng c\u1ee7a s\u1ea3n ph\u1ea9m, \u0111\u00f3 l\u00e0 t\u1ed1c \u0111\u1ed9. T\u1ed1c \u0111\u1ed9 th\u01b0\u1eddng \u0111o b\u1eb1ng bit\/gi\u00e2y ho\u1eb7c kbit\/gi\u00e2y (1 k= 1000). V\u00ed d\u1ee5 2 kbit\/gi\u00e2y bi\u1ec3u th\u1ecb m\u00f4\u0111em m\u1ed7i gi\u00e2y c\u00f3 th\u1ec3 truy\u1ec1n t\u1ea3i 2000 con s\u1ed1 h\u1ec7 \u0111\u1ebfm nh\u1ecb ph\u00e2n (2000 bit). T\u1ed1c \u0111\u1ed9 c\u1ee7a m\u00f4\u0111em c\u00e0ng nhanh th\u00ec ch\u00fang ta v\u00e0o m\u1ea1ng ho\u1eb7c trao \u0111\u1ed5i v\u0103n ki\u1ec7n c\u00e0ng ti\u1ec7n l\u1ee3i. Kho\u1ea3ng 20 n\u0103m tr\u01b0\u1edbc, khi m\u00f4\u0111em ra \u0111\u1eddi th\u00ec t\u1ed1c \u0111\u1ed9 ch\u1ec9 l\u00e0 300 bit\/gi\u00e2y. Ng\u00e0y nay tr\u00ean th\u1ecb tr\u01b0\u1eddng th\u01b0\u1eddng th\u1ea5y m\u00f4\u0111em c\u00f3 lo\u1ea1i 33,6 kbit\/s v\u00e0 56 kbit\/s. V\u1eady th\u00ec t\u1ed1c \u0111\u1ed9 m\u00f4\u0111em do c\u00e1i g\u00ec quy\u1ebft \u0111\u1ecbnh v\u1eady? Sau n\u00e0y c\u00f2n s\u1ebd t\u0103ng l\u00ean n\u1eefa kh\u00f4ng?<\/p>\n\n\n\n
Th\u00f4ng tin s\u1edf d\u0129 \u0111\u1ea1t \u0111\u01b0\u1ee3c t\u1ed1c \u0111\u1ed9 t\u1ed1i \u0111a l\u00e0 b\u1edfi m\u00f4i gi\u1edbi gi\u1eefa b\u00ean thu v\u00e0 b\u00ean ph\u00e1t – \u0111\u01b0\u1eddng truy\u1ec1n th\u00f4ng quy\u1ebft \u0111\u1ecbnh. V\u00ed d\u1ee5 ch\u00fang ta n\u00f3i chuy\u1ec7n, t\u1ed1c \u0111\u1ed9 li\u00ean l\u1ea1c quy\u1ebft \u0111\u1ecbnh b\u1edfi vi\u1ec7c ch\u00fang ta n\u00f3i c\u00f3 nhanh (m\u1ea5y \u00e2m ti\u1ebft m\u1ed9t ph\u00fat) v\u00e0 m\u1ed7i \u00e2m ti\u1ebft c\u00f3 th\u1ec3 bi\u1ec3u \u0111\u1ea1t \u0111\u01b0\u1ee3c bao nhi\u00eau \u00fd ngh\u0129a. N\u1ebfu h\u1ed3i \u00e2m trong ph\u00f2ng l\u00e0 \u0111\u00e1ng s\u1ee3 th\u00ec ch\u00fang ta kh\u00f4ng th\u1ec3 n\u00f3i nhanh \u0111\u01b0\u1ee3c, n\u1ebfu kh\u00f4ng \u00e2m tr\u01b0\u1edbc \u00e2m sau s\u1ebd l\u1eabn v\u00e0o nhau. Hi\u1ec7u \u1ee9ng h\u1ed3i \u00e2m n\u00e0y trong truy\u1ec1n th\u00f4ng \u0111o b\u1eb1ng “h\u01b0\u1edfng \u1ee9ng t\u1ea7n s\u1ed1” (\u0111\u00e1p \u1ee9ng t\u1ea7n). M\u1eb7t kh\u00e1c ti\u1ebfng \u1ed3n xung quanh qu\u00e1 to m\u00e0 ch\u00fang ta l\u1ea1i kh\u00f4ng th\u1ec3 n\u00f3i to h\u01a1n n\u1eefa th\u00ec ch\u00fang ta n\u00ean tr\u00e1nh d\u00f9ng nh\u1eefng \u00e2m ti\u1ebft g\u1ea7n v\u1edbi \u00e2m thanh, \u0111\u1ec3 kh\u1ecfi b\u1ecb nghe nh\u1ea7m. Nh\u01b0 v\u1eady s\u1ebd gi\u1ea3m thi\u1ec3u \u00fd ngh\u0129a m\u00e0 m\u1ed7i \u00e2m ti\u1ebft c\u00f3 th\u1ec3 bi\u1ec3u \u0111\u1ea1t. Trong th\u00f4ng tin, ta l\u1ea5y “t\u1ec9 su\u1ea5t \u1ed3n tin” (t\u1ef7 s\u1ed1 t\u00edn\/t\u1ea1p) \u0111\u1ec3 \u0111o \u1ea3nh h\u01b0\u1edfng c\u1ee7a ti\u1ebfng \u1ed3n \u0111\u1ed1i v\u1edbi t\u00edn hi\u1ec7u. H\u01b0\u1edfng \u1ee9ng t\u1ea7n s\u1ed1 c\u1ee7a \u0111\u01b0\u1eddng truy\u1ec1n tin v\u00e0 t\u1ec9 su\u1ea5t \u1ed3n tin l\u00e0 th\u00f4ng s\u1ed1 quan tr\u1ecdng \u1ea3nh h\u01b0\u1edfng t\u1edbi t\u1ed1c \u0111\u1ed9 truy\u1ec1n th\u00f4ng.<\/p>\n\n\n\n
\u0110\u01b0\u01a1ng nhi\u00ean c\u00f9ng m\u1ed9t \u0111\u01b0\u1eddng truy\u1ec1n th\u00ec t\u1ed1c \u0111\u1ed9 truy\u1ec1n th\u00f4ng c\u00f3 li\u00ean quan c\u1ea3 t\u1edbi ph\u01b0\u01a1ng th\u1ee9c s\u1eed d\u1ee5ng. Ph\u01b0\u01a1ng th\u1ee9c n\u00e0y trong truy\u1ec1n th\u00f4ng g\u1ecdi l\u00e0 k\u1ef9 thu\u1eadt ghi m\u00e3. S\u1ef1 hay d\u1edf c\u1ee7a vi\u1ec7c ghi m\u00e3 tr\u1ef1c ti\u1ebfp \u1ea3nh h\u01b0\u1edfng t\u1edbi t\u1ed1c \u0111\u1ed9 th\u00f4ng tin. N\u0103m 1948, nh\u00e0 khoa h\u1ecdc Shannon thu\u1ed9c ph\u00f2ng th\u00ed nghi\u1ec7m [Bell (Alexander Graham Bell (1847 – 1922) nh\u00e0 ph\u00e1t minh \u0111i\u1ec7n tho\u1ea1i] \u0111\u00e3 s\u00e1ng l\u1eadp ra l\u00ed thuy\u1ebft th\u00f4ng tin, n\u00eau ra ph\u01b0\u01a1ng ph\u00e1p t\u00ednh to\u00e1n t\u1ed1c \u0111\u1ed9 truy\u1ec1n t\u1ea3i gi\u1edbi h\u1ea1n d\u1ef1a theo t\u1ec9 su\u1ea5t \u1ed3n c\u1ee7a tin v\u00e0 \u0111\u00e1p \u1ee9ng t\u1ea7n s\u1ed1 c\u1ee7a m\u1ed9t \u0111\u01b0\u1eddng truy\u1ec1n. Ch\u1ec9 khi t\u1ed1c \u0111\u1ed9 truy\u1ec1n t\u1ea3i th\u1ea5p h\u01a1n gi\u1edbi h\u1ea1n n\u00e0y th\u00ec ch\u00fang ta m\u1edbi c\u00f3 th\u1ec3 truy\u1ec1n d\u1eef li\u1ec7u kh\u00f4ng sai s\u00f3t. Th\u1ebf nh\u01b0ng, \u0111\u1ebfn nay ng\u01b0\u1eddi ta v\u1eabn ch\u01b0a t\u00ecm th\u1ea5y m\u1ed9t ph\u01b0\u01a1ng ph\u00e1p th\u00f4ng th\u01b0\u1eddng n\u00e0o \u0111\u1ea1t t\u1edbi gi\u1edbi h\u1ea1n n\u00e0y. V\u1edbi m\u1ed7i \u0111\u01b0\u1eddng truy\u1ec1n c\u1ee5 th\u1ec3, ch\u00fang ta c\u1ea7n ph\u1ea3i t\u00ecm ra ph\u01b0\u01a1ng ph\u00e1p th\u00edch h\u1ee3p \u0111\u1ec3 s\u1eeda ch\u1eefa nh\u1eefng sai l\u1ea7m trong khi truy\u1ec1n t\u00edn hi\u1ec7u, v\u00e0 th\u00f4ng qua m\u00e3 ghi \u0111\u1ec3 ph\u00e1t hi\u1ec7n v\u00e0 s\u1eeda ch\u1eefa nh\u1eefng sai l\u1ea7m do ti\u1ebfng \u1ed3n t\u1ea1o n\u00ean. C\u00f9ng v\u1edbi s\u1ef1 ph\u00e1t tri\u1ec3n kh\u00f4ng ng\u1eebng c\u1ee7a k\u1ef9 thu\u1eadt n\u00e0y, t\u1ed1c \u0111\u1ed9 truy\u1ec1n t\u1ea3i d\u1eef li\u1ec7u \u0111\u00e3 n\u00e2ng cao kh\u00f4ng ng\u1eebng, t\u1eeb tho\u1ea1t \u0111\u1ea7u l\u00e0 300 bit\/gi\u00e2y \u0111\u1ebfn 1200, 2400, 9600, 14400, 19200 bit\/gi\u00e2y. V\u1edbi \u0111\u01b0\u1eddng d\u00e2y \u0111i\u1ec7n tho\u1ea1i hi\u1ec7n nay \u0111\u1ea1t t\u1edbi 33,64 Kbit\/gi\u00e2y \u0111\u00e3 l\u00e0 ti\u1ebfp c\u1eadn gi\u1edbi h\u1ea1n Shannon r\u1ed3i.<\/p>\n\n\n\n
V\u1eady th\u00ec ch\u00fang ta l\u00e0m sao v\u01b0\u1ee3t qua gi\u1edbi h\u1ea1n Shannon \u0111\u1ec3 \u0111\u1ea1t t\u1ed1c \u0111\u1ed9 56 Kbit\/gi\u00e2y \u0111\u00e2y? \u0110\u00f3 l\u00e0 s\u1eed d\u1ee5ng t\u00ednh \u0111\u1eb7c th\u00f9 c\u1ee7a \u0111\u01b0\u1eddng d\u00e2y \u0111i\u1ec7n tho\u1ea1i. Ng\u00e0y nay tuy\u1ec7t \u0111\u1ea1i b\u1ed9 ph\u1eadn m\u1ea1ng \u0111i\u1ec7n tho\u1ea1i \u0111\u1ec1u l\u00e0 ki\u1ec3u s\u1ed1, l\u1eddi n\u00f3i c\u1ee7a ng\u01b0\u1eddi d\u00f9ng m\u00e1y ho\u1eb7c t\u00edn hi\u1ec7u c\u1ee7a m\u00f4\u0111em \u0111\u1ec1u l\u00e0 \u0111i\u1ec7n \u00e1p bi\u1ebfn \u0111\u1ed5i li\u00ean t\u1ee5c, g\u1ecdi l\u00e0 t\u00edn hi\u1ec7u t\u01b0\u01a1ng t\u1ef1 (analog). Th\u00f4ng th\u01b0\u1eddng, n\u00f3 \u0111\u01b0\u1ee3c \u0111\u01b0a t\u1edbi tr\u1ea1m \u0111i\u1ec7n tho\u1ea1i b\u1eb1ng \u0111\u01b0\u1eddng d\u00e2y \u0111i\u1ec7n tho\u1ea1i b\u00ecnh th\u01b0\u1eddng (g\u1ecdi l\u00e0 v\u00f2ng n\u1ed9i h\u1ea1t). T\u1ea1i m\u00e1y t\u1ed5ng \u0111\u00e0i s\u1ed1 c\u1ee7a b\u01b0u \u0111i\u1ec7n, nh\u1eefng \u0111i\u1ec7n \u00e1p n\u00e0y \u0111\u01b0\u1ee3c bi\u1ebfn \u0111\u1ed5i th\u00e0nh t\u00edn hi\u1ec7u s\u1ed1 (g\u1ecdi l\u00e0 l\u01b0\u1ee3ng t\u1eed h\u00f3a), r\u1ed3i b\u1eb1ng m\u1ea1ng s\u1ed1 gi\u1eefa c\u00e1c tr\u1ea1m m\u00e0 chuy\u1ec3n t\u1edbi tr\u1ea1m n\u01a1i c\u00f3 ng\u01b0\u1eddi nh\u1eadn \u0111i\u1ec7n. \u1ede \u0111\u00e2y, nh\u1eefng t\u00edn hi\u1ec7u s\u1ed1 n\u00e0y l\u1ea1i \u0111\u01b0\u1ee3c ho\u00e0n nguy\u00ean th\u00e0nh t\u00edn hi\u1ec7u t\u01b0\u01a1ng t\u1ef1, truy\u1ec1n t\u1edbi ng\u01b0\u1eddi nh\u1eadn \u0111i\u1ec7n qua v\u00f2ng n\u1ed9i h\u1ea1t. Qu\u00e1 tr\u00ecnh l\u01b0\u1ee3ng h\u00f3a k\u1ec3 tr\u00ean l\u00e0 kh\u00f4ng ch\u00ednh x\u00e1c cho l\u1eafm. Trong h\u1ec7 th\u1ed1ng \u0111i\u1ec7n tho\u1ea1i, m\u1ed7i m\u1ed9t t\u00edn hi\u1ec7u t\u01b0\u01a1ng t\u1ef1 ch\u1ec9 b\u1ecb l\u01b0\u1ee3ng t\u1eed h\u00f3a th\u00e0nh 8 h\u00e0ng s\u1ed1 thu\u1ed9c h\u1ec7 nh\u1ecb ph\u00e2n. Khi l\u01b0\u1ee3ng t\u1eed h\u00f3a, m\u00e1y trao \u0111\u1ed5i d\u1ef1a v\u00e0o t\u00edn hi\u1ec7u t\u01b0\u01a1ng t\u1ef1 m\u00e0 ng\u01b0\u1eddi d\u00f9ng m\u00e1y \u0111\u01b0a t\u1edbi \u0111\u1ec3 ph\u00e1t ra con s\u1ed1 \u0111\u1ed1i \u1ee9ng c\u00f3 gi\u00e1 tr\u1ecb gi\u1ea3 thi\u1ebft g\u1ea7n v\u1edbi n\u00f3. C\u00f2n cu\u1ed1i c\u00f9ng th\u00ec ng\u01b0\u1eddi nh\u1eadn \u0111i\u1ec7n s\u1ebd nh\u1eadn \u0111\u01b0\u1ee3c ch\u00ednh gi\u00e1 tr\u1ecb gi\u1ea3 thi\u1ebft n\u00e0y. B\u1edfi th\u1ebf, \u0111i\u1ec7n tho\u1ea1i m\u00e0 ng\u01b0\u1eddi s\u1eed d\u1ee5ng ph\u00e1t \u0111i th\u1ef1c t\u1ebf c\u00f3 s\u1ef1 kh\u00e1c bi\u1ec7t v\u1edbi gi\u00e1 tr\u1ecb gi\u1ea3 thi\u1ebft m\u00e0 m\u00e1y bi\u1ebfn \u0111\u1ed5i ch\u1ecdn l\u1ef1a, v\u00e0 tr\u1edf th\u00e0nh sai s\u00f3t ho\u1eb7c ti\u1ebfng \u1ed3n trong \u0111\u01b0\u1eddng truy\u1ec1n. Ta g\u1ecdi \u0111\u00f3 l\u00e0 ti\u1ebfng \u1ed3n l\u01b0\u1ee3ng t\u1eed h\u00f3a. Ki\u1ec3u truy\u1ec1n t\u1ea3i ng\u1eef \u00e2m theo thi\u1ebft k\u1ebf<\/a> n\u00e0y kh\u00e1 l\u00ed t\u01b0\u1edfng, nh\u01b0ng \u0111\u1ed1i v\u1edbi thi\u1ebft b\u1ecb m\u00f4\u0111em truy\u1ec1n th\u1ed1ng (33,6 K bit\/gi\u00e2y) th\u00ec ti\u1ebfng \u1ed3n l\u01b0\u1ee3ng t\u1eed h\u00f3a \u0111\u00e3 t\u1ea1o n\u00ean nguy\u00ean nh\u00e2n ch\u1ee7 y\u1ebfu c\u1ee7a ti\u1ebfng \u1ed3n \u0111\u01b0\u1eddng truy\u1ec1n, do v\u1eady \u0111\u00e3 h\u1ea1n ch\u1ebf t\u1ed1c \u0111\u1ed9 cao nh\u1ea5t c\u1ee7a m\u00f4\u0111em.<\/p>\n\n\n\n K\u1ef9 thu\u1eadt 56 Kbit\/gi\u00e2y th\u00ec kh\u00e1c h\u1eb3n. K\u1ef9 thu\u1eadt n\u00e0y \u0111\u00f2i h\u1ecfi m\u1ed9t b\u00ean th\u00f4ng tin ph\u1ea3i tr\u1ef1c ti\u1ebfp n\u1ed1i v\u1edbi m\u1ea1ng \u0111i\u1ec7n tho\u1ea1i s\u1ed1. Th\u00f4ng th\u01b0\u1eddng \u0111\u00f3 l\u00e0 nh\u00e0 cung c\u1ea5p d\u1ecbch v\u1ee5 Internet (ISP). C\u00f2n ng\u01b0\u1eddi s\u1eed d\u1ee5ng ch\u00fang ta th\u00ec h\u00f2a m\u1ea1ng \u0111i\u1ec7n tho\u1ea1i qua v\u00f2ng n\u1ed9i h\u1ea1t. \u1ede h\u01b0\u1edbng truy\u1ec1n xu\u1ed1ng (h\u01b0\u1edbng t\u1eeb ISP \u0111\u1ebfn ng\u01b0\u1eddi d\u00f9ng), b\u00ean ph\u00e1t tin tr\u1ef1c ti\u1ebfp \u0111\u01b0a s\u1ed1 li\u1ec7u v\u00e0o m\u1ea1ng \u0111i\u1ec7n tho\u1ea1i s\u1ed1 m\u00e0 kh\u00f4ng qua l\u01b0\u1ee3ng t\u1eed h\u00f3a. M\u00f4\u0111em ng\u01b0\u1eddi s\u1eed d\u1ee5ng ch\u1ec9 c\u1ea7n d\u1ef1a v\u00e0o t\u00edn hi\u1ec7u t\u01b0\u01a1ng t\u1ef1 \u0111\u00e3 thu \u0111\u01b0\u1ee3c m\u00e0 x\u00e1c \u0111\u1ecbnh r\u00f5 c\u00e1i chuy\u1ec3n t\u1edbi t\u1eeb m\u00e1y bi\u1ebfn \u0111\u1ed5i l\u00e0 gi\u00e1 tr\u1ecb gi\u1ea3 thi\u1ebft n\u00e0o, v\u00e0 s\u1ebd c\u00f3 \u0111\u01b0\u1ee3c d\u1eef li\u1ec7u c\u1ea7n ti\u1ebfp nh\u1eadn. C\u00f2n h\u01b0\u1edbng truy\u1ec1n l\u00ean (c\u00e1c thu\u00ea bao t\u1edbi c\u00e1c ISP) th\u00ec v\u1eabn ph\u1ea3i l\u01b0\u1ee3ng t\u1eed h\u00f3a. Cho n\u00ean c\u0169ng v\u1eabn d\u00f9ng k\u1ef9 thu\u1eadt truy\u1ec1n th\u1ed1ng. T\u1ed1c \u0111\u1ed9 t\u1ed1i \u0111a l\u00e0 31,2 Kbit\/gi\u00e2y. B\u1edfi ph\u1ea7n l\u1edbn thu\u00ea bao r\u1ea5t \u00edt v\u0103n ki\u1ec7n truy\u1ec1n l\u00ean m\u00e0 s\u1ef1 s\u1eafp \u0111\u1eb7t phi \u0111\u1ed1i x\u1ee9ng n\u00e0y l\u00e0 t\u01b0\u01a1ng \u0111\u1ed1i th\u00edch h\u1ee3p.<\/p>\n\n\n\n Do v\u1eady ta th\u1ea5y, ch\u00fang ta s\u1edf d\u0129 \u0111\u1ea1t \u0111\u01b0\u1ee3c t\u1ed1c \u0111\u1ed9 \u0111\u01b0\u1eddng truy\u1ec1n cao l\u00e0 v\u00ec \u0111\u01b0\u1eddng truy\u1ec1n ng\u00e0y nay \u0111\u00e3 kh\u00e1c v\u1edbi tr\u01b0\u1edbc kia. \u0110i\u1ec1u n\u00e0y kh\u00f4ng ng\u01b0\u1ee3c v\u1edbi l\u00ed thuy\u1ebft Shannon. Dung l\u01b0\u1ee3ng m\u00e0 m\u1ea1ng \u0111i\u1ec7n tho\u1ea1i c\u1ea5p cho m\u1ed7i thu\u00ea bao l\u00e0 64 Kbit\/gi\u00e2y. Ch\u00fang ta l\u1ea1i ph\u1ea3i hy sinh m\u1ed9t s\u1ed1 t\u1ed1c \u0111\u1ed9 \u0111\u1ec3 b\u00f9 l\u1ea5p l\u1ea1i s\u1ef1 th\u1ea5t tho\u00e1t c\u1ee7a \u0111\u01b0\u1eddng truy\u1ec1n c\u1ee7a v\u00f2ng n\u1ed9i h\u1ea1t. T\u1ed1c \u0111\u1ed9 56 Kbit\/gi\u00e2y c\u0169ng g\u1ea7n \u0111\u1ea1t t\u1edbi gi\u1edbi h\u1ea1n c\u1ee7a k\u1ef9 thu\u1eadt n\u00e0y.<\/p>\n\n\n\n \u0110i\u1ec1u c\u1ea7n l\u01b0u \u00fd l\u00e0 t\u1ed1c \u0111\u1ed9 56 Kbit\/gi\u00e2y kh\u00f4ng ph\u1ea3i l\u00e0 n\u01a1i n\u00e0o c\u0169ng \u0111\u1ea1t \u0111\u01b0\u1ee3c, c\u00f3 r\u1ea5t nhi\u1ec1u nh\u00e2n t\u1ed1 \u0111\u1ec1u c\u00f3 th\u1ec3 khi\u1ebfn ta kh\u00f4ng c\u00f3 \u0111\u01b0\u1ee3c t\u1ed1c \u0111\u1ed9 cao nh\u1ea5t. Th\u00f4ng th\u01b0\u1eddng, n\u1ebfu \u0111\u1ea1t \u0111\u01b0\u1ee3c h\u01a1n 40 Kbit\/gi\u00e2y \u0111\u00e3 l\u00e0 kh\u00e1 r\u1ed3i.<\/p>\n\n\n\n T\u00f3m l\u1ea1i, hi\u1ec7n nay t\u1ed1c \u0111\u1ed9 c\u1ee7a m\u00f4\u0111em \u0111\u00e3 g\u1ea7n t\u1edbi gi\u1edbi h\u1ea1n, kh\u1ea3 n\u0103ng c\u1ee7a h\u1ec7 th\u1ed1ng \u0111i\u1ec7n tho\u1ea1i.<\/p>\n\n\n\n Mu\u1ed1n n\u00e2ng cao h\u01a1n n\u1eefa th\u00ec ph\u1ea3i s\u1eed d\u1ee5ng k\u1ef9 thu\u1eadt ISDN, DSL.<\/p>\n\n\n\n C\u00f2n c\u00f3 m\u1ed9t \u0111i\u1ec3m c\u1ea7n n\u00f3i r\u00f5 l\u00e0 t\u1ed1c \u0111\u1ed9 bi\u1ec3u th\u1ecb c\u1ee7a m\u00f4\u0111em kh\u00f4ng th\u1ec3 b\u1eb1ng v\u1edbi t\u1ed1c \u0111\u1ed9 truy\u1ec1n t\u1ea3i v\u0103n ki\u1ec7n th\u1ef1c t\u1ebf. Nguy\u00ean nh\u00e2n l\u00e0, tr\u01b0\u1edbc h\u1ebft m\u00f4\u0111em s\u1ebd d\u1ef1a v\u00e0o ch\u1ea5t l\u01b0\u1ee3ng \u0111\u01b0\u1eddng d\u00e2y m\u00e0 t\u1ef1 \u0111\u1ed9ng ch\u1ecdn l\u1ef1a t\u1ed1c \u0111\u1ed9 t\u1ed1i \u01b0u, kh\u00f4ng ph\u1ea3i l\u00fac n\u00e0o c\u0169ng ch\u1ecdn t\u1ed1c \u0111\u1ed9 cao nh\u1ea5t. Th\u1ee9 \u0111\u1ebfn, t\u00ecnh h\u00ecnh b\u1ed9 ph\u1eadn kh\u00e1c c\u1ee7a m\u1ea1ng nh\u01b0 t\u1ed1c \u0111\u1ed9 Internet, ISP v\u00e0 ph\u1ee5 t\u1ea3i c\u1ee7a tr\u1ea1m t\u1edbi, v\u00e0 c\u1ea3 t\u1ed1c \u0111\u1ed9 giao di\u1ec7n gi\u1eefa m\u00e1y t\u00ednh v\u00e0 m\u00f4\u0111em \u0111\u1ec1u c\u00f3 th\u1ec3 \u1ea3nh h\u01b0\u1edfng t\u1edbi t\u1ed1c \u0111\u1ed9 truy\u1ec1n t\u1ea3i cu\u1ed1i c\u00f9ng. Ngo\u00e0i ra, t\u00ednh c\u00f3 th\u1ec3 n\u00e9n c\u1ee7a lo\u1ea1i v\u0103n ki\u1ec7n truy\u1ec1n t\u1ea3i c\u0169ng l\u00e0 m\u1ed9t nh\u00e2n t\u1ed1 \u1ea3nh h\u01b0\u1edfng quan tr\u1ecdng. (Hi\u1ec7n nay ng\u01b0\u1eddi ta \u0111\u00e3 d\u00f9ng m\u00f4\u0111em ADSL m\u1ed9t c\u1ed5ng ho\u1eb7c b\u1ed1n c\u1ed5ng – btv.)<\/p>\n\n\n\n T\u1eeb kh\u00f3a: M\u00f4\u0111em; T\u00edn hi\u1ec7u t\u01b0\u01a1ng t\u1ef1; Ti\u1ebfng \u1ed3n l\u01b0\u1ee3ng t\u1eed h\u00f3a.<\/p>\n","protected":false},"excerpt":{"rendered":" Khi ch\u1ecdn mua m\u00f4\u0111em, ch\u00fang ta s\u1ebd ch\u00fa \u00fd t\u1edbi m\u1ed9t ch\u1ec9 ti\u00eau r\u1ea5t quan tr\u1ecdng c\u1ee7a s\u1ea3n ph\u1ea9m, \u0111\u00f3 l\u00e0 t\u1ed1c \u0111\u1ed9. T\u1ed1c \u0111\u1ed9 th\u01b0\u1eddng \u0111o b\u1eb1ng bit\/gi\u00e2y ho\u1eb7c kbit\/gi\u00e2y (1 k= 1000). V\u00ed d\u1ee5 2 kbit\/gi\u00e2y bi\u1ec3u th\u1ecb m\u00f4\u0111em m\u1ed7i gi\u00e2y c\u00f3 th\u1ec3 truy\u1ec1n t\u1ea3i 2000 con s\u1ed1 h\u1ec7 \u0111\u1ebfm nh\u1ecb ph\u00e2n (2000 […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":"","_disable_autopaging":false},"categories":[15,13],"tags":[],"class_list":["post-10328","post","type-post","status-publish","format-standard","hentry","category-hoi-dap-khoa-hoc","category-tin-hoc"],"_links":{"self":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/10328","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/comments?post=10328"}],"version-history":[{"count":0,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/posts\/10328\/revisions"}],"wp:attachment":[{"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/media?parent=10328"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/categories?post=10328"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.vietlearn.org\/kien-thuc\/wp-json\/wp\/v2\/tags?post=10328"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}