Bi vit v IP Telephony trong chng trnh CCNP-Switching. Cc bn c th download ni dung trong file *.pdf nh km.--------------------------------------------------------------------

Catalyst switch c th cung cp ngun cho cc IP phones, hnh thnh cc kt ni trunking vi IP phones, cung cp mt mc QoS cho cc voice packets.

I. Inline power

Mt thit b Cisco IP Phones cng ging nh tt c cc node khc trong h thng mng ch thit b phi c ngun in hot ng. Ngun in c th n t hai ni:

- T mt ngun AC adapter.- T ngun DC trch ra t cp mng (data cable).

Trong cch th nht, mt adapter s chuyn i in AC 220V sang 48V DC cho phones hot ng. Nu b cp in, IP phones s khng hot ng.

Gii php th hai cn gi l inline power. Khi ny, ngun 48 V DC s c cung cp n IP phones trn cng cp mng UTP c dng kt ni Ethernet. Ngun in DC trong trng hp ny chnh l Catalyst switch. u im ca cch ny l ngun in c th c qun l, gim st ch cho IP phones. Nu mt my PC bnh thng c gn vo cng switchport, ngun in s khng c cp cho PC. Catalyst switch cng c th gn vo mt b lu in UPS; iu ny cho php IP phones vn hot ng ngay khi cp in.

Khi mt switch c bt ln, switch s gi ra mt tn hiu test-tone 340-kHz trn i si cp truyn ca cp UTP. y l cch m switch tm ra thit b c gn vo port ca n c kh nng power-in-line hay khng.

Thit b IP-Phone s ni tt cp cp truyn v nhn. Khi IP phones c ni vo mt switch-port, switch s nghe thy tn hiu test-tone c loop li. Switch s kt lun l c mt thit b ang tn ti v c th cp ngun cho thit b ny. Ngun in s c cp trn cp s 2 v 3 (RJ-45 pins 1,2 and 3,6) at 48V DC.

Tnh nng power inline c trong switch 3550-24-PWR, Catalyst 4500 v Catalyst 6500.

Switch cng c th cung cp mt cng sut ngun mc nh cho cc thit b phones gn vo n. V d mt IP phones u tin nhn mt cng sut l 15.0watts. (.36amps, 48V DC). Switch sau s c gng gi cc CDP messge cho thit b. Cc CDP frame ny nhm mc ch kim tra xem cng sut thc s cn bi IP phones.

Cu hnh Inline power:

Mi switch port s t ng pht hin s tn ti ca mt thit b c kh nng dng power-inline.

Switch(config-if)#power inline {auto|never}

II. Voice VLAN:

Cisco IP phones s to ra mt lung d liu cho voice (voice data stream). Thm vo , n cung cp mt kt ni cho PCs ca ngi dng. iu ny cho php mt port Ethernet duy nht c th c ci t cho mi ngi dng (1 data + 1 voice). Voice v userPC lun hot ng access-mode.

Kt ni gia IP phone v switch s c iu chnh: bn c th cu hnh switch ra lnh cho IP phones dng dng 802.1q trunk hoc nh l mt access-link bnh thng. Nu dng kt ni trunking, d liu voice c th c tch ra khi cc d liu khc ca ngi dng. Nu nh l mt access-link, c data v voice phi c kt hp trong mt VLAN duy nht.

III. Cu hnh Voice-VLAN:

Phn ny s kho st d liu voice s c ng gi nh th no. Cc gi voice (voice packets) s c mang trong mt VLAN duy nht gi l Voice VLAN hoc trn mt data VLAN bnh thng, gi l native VLAN. Thng tin QoS t voice packets cng phi c mang theo trong cc packets.C 4 giao thc c dng bi CallManager v cc tht b IP Phone:

H.323 Protocol

Media Gateway Control Protocol (MGCP)

Skinny Client Control Protocol (SCCP)

Session Initiation Protocol (SIP)

H.323 Protocol

T chc ITU pht trin giao thc H323 cho php cc ng dng truyn thng a phng tin c th hot ng trn mng IP. V H323 l mt chun m nn c nhiu nh sn xut h tr. c t ca H323 bao gm tt c cc kha cnh nh cc dch v, signaling v cc kim sot ca cc phin lm vic. Thoi (audi) l mt chun trn H323 nhng mng cng c th m rng bao gm video v c data. Giao thc H323 c th c hin thc trong nhng mng doanh nghip ln hoc c th trin khai trn nhng h tng mng c sn.

Cc thnh phn c bn ca H323 l terminals, gateways, and gatekeepers (kim sot cuc gi n cc thit b u cui H.323 endpoints).

Cng ging nh cc giao thc khc, H323 p t vo cc kt ni point-to-point hoc cc kt ni multipoint. Tuy nhin nu so snh vi MGCP, H323 s i hi nhiu cu hnh trn gateway.