ATM Direct Mapping - CRC4 - No CRC4 Nedir

[heavenix]

arkadaşlar selam
e1 config.lerde kullanılan crc4 ve no crc4 hakkında bilgisi olan var mıdır?

Bu ikisinin farkı nedir? crc hata kontrolü yaparken no crc4 olarak ayarlarsak devrede hata kontrolü olmuyor mu?

[burner]

Slm;

G.703—Defines electrical and physical properties of an E1 interface. Electrical properties are specifications such as pulse shape, impedance, and peak voltage. Cisco IMA interfaces support G.703 as the basic electrical specification with crc4adm and pcm30adm framing.

G.704—Defines the framing format of an E1 interface as well as other bit rates, such as 1.544 Mbps (T1) and 44.736 Mbps (DS-3).

G.804—Defines how to map ATM cells into E1 frames in the 30 time slots that are available for user data and are not reserved.


Non-ATM interfaces specify a different set of framing formats because you do not need to specify how to map the ATM cells into the E1 frame. On non-ATM Cisco router interfaces—such as the PA-MC-2E1—specify E1 framing by issuing the framing {crc4 | no-crc4} configuration subcommand, as in this example:

router(config-controller)# framing crc4

When transmitting ATM cells over a digital interface like E1, you map the cells into the physical-layer frame. In the case of an E1 interface, you map the cells directly into the frame. ITU-T Recommendation G.804 and ATM Forum specification af-phy-0064.000 define this ATM direct mapping (ADM) process. ADM uses the header error check (HEC) field in the cell header to identify the first bit of a cell in an E1 frame. A receiving E1 IMA interface examines the incoming bit stream and checks if a set of eight bits comprises a valid CRC for the preceding 32 bits.

For More info:

h**p://www.cisco.com/univercd/cc/td/doc/product/software/ios113ed/cs/csprtd/csprtd1/cssyncs.htm


Iyi gunler

[Orhan ERGUN]

Mrb ,

Atm hucrelerinin E1 cerceveleri üzerinde taşınması sırasında , hata kontrolu yapılması yada yapılmamasına gore , cercevelemeyi yani framing'i crc4 yada no crc4 yaparız. Turk telekom'un eski tip santrallerinde crc yapamıyorsunuz ,bu nedenle e1 trunku olustururken santral parametreleriyle aynı set edilmesi gerekiyor.

E1 bağlantısı up olmuyorsa , framing nocrc4 olarak set ediyoruz.

Kolay Gelsin

[heavenix]

açıklamalar için teşekkürler.