如何實(shí)現(xiàn)DS34S132與其它TDMoP器件的互操作
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互操作性是一個系統(tǒng)經(jīng)過很少甚至無需系統(tǒng)操作員介入而實(shí)現(xiàn)與其它系統(tǒng)協(xié)同工作的能力。系統(tǒng)的互操作性使其有可能為其它系統(tǒng)提供服務(wù)或接受其它系統(tǒng)的服務(wù),使得不同廠商的系統(tǒng)能夠協(xié)同工作。本應(yīng)用筆記介紹如何設(shè)置DS34S132 TDM-over-Packet (TDMoP) IC，使其與其它TDMoP器件實(shí)現(xiàn)互操作。
引言
毋庸諱言，當(dāng)今的通信系統(tǒng)需要不同設(shè)備和設(shè)備之間的復(fù)雜交互。隨著技術(shù)的進(jìn)步，互操作性也變得更加重要。互操作性是一個系統(tǒng)經(jīng)過很少甚至無需系統(tǒng)操作員介入而實(shí)現(xiàn)與其它系統(tǒng)協(xié)同工作的能力。系統(tǒng)的互操作性使其有可能為其它系統(tǒng)提供服務(wù)或接受其它系統(tǒng)的服務(wù)，從而使不同廠商的系統(tǒng)能夠協(xié)同工作。
本應(yīng)用筆記著重介紹Maxim TDM-over-Packet (TDMoP) IC，DS34S132。文章介紹了在DS34S132與其他廠商TDMoP器件之間實(shí)現(xiàn)互操作性的設(shè)置要求。
互操作性要求
Maxim的TDMoP器件產(chǎn)生的數(shù)據(jù)包與其他廠商的TDMoP器件的報(bào)頭信息可能不同。為了使TDMoP器件實(shí)現(xiàn)互操作，用戶需要了解器件的設(shè)置類型。Maxim器件的設(shè)置為以下之一：
- IP/UDP/RTP/SAToP
- IP/UDP/RTP/CESoPSN
- MEF/RTP/CESoETH—非結(jié)構(gòu)化(即MEF/SAToP)
- MEF/RTP/CESoETH—結(jié)構(gòu)化鎖定(即MEF/CESoPSN)
- MPLS/RTP/SAToP—非結(jié)構(gòu)化(即MPLS/RTP/SAToP)
- MPLS/RTP/CESoPSN—結(jié)構(gòu)化鎖定(即MPLS/RTP/CESoPSN)
每種TDMoP器件設(shè)置都有不同的報(bào)頭。為了實(shí)現(xiàn)互操作性，必須將來自于Maxim TDMoP器件的報(bào)頭格式化，使其與其它器件的報(bào)頭相同。這意味著用戶需要比較TDMoP器件的報(bào)頭，并查找格式差異。本應(yīng)用筆記介紹如何利用Maxim的應(yīng)用程序修改DS34S132 TDMoP器件的報(bào)頭。文章還介紹了如何修改Maxim綁定配置，以接受協(xié)議相同但報(bào)頭信息不同的數(shù)據(jù)包。
TDMoP格式
本節(jié)介紹TDM-over-Packet模塊的功能描述。為了通過分組交換網(wǎng)絡(luò)傳輸TDM數(shù)據(jù)，TDMoP器件將TDM數(shù)據(jù)封裝為以太網(wǎng)數(shù)據(jù)包，如圖1所示。TDMoP報(bào)頭不同數(shù)據(jù)塊的說明請參見表1。
圖1. 以太網(wǎng)數(shù)據(jù)包格式的TDMoP封裝。
表1. 以太網(wǎng)數(shù)據(jù)包結(jié)構(gòu)
| Field | Description |
| Preamble | A sequence of 56 bits (alternating 1 and 0 values) used for synchronization. Gives components in the network time to detect the presence of a signal. |
| Start frame delimiter | A sequence of 8 bits (10101011) that indicates the start of the packet. |
| Destination and Source Addresses | The Destination Address field identifies the station or stations that are to receive the packet. The Source Address identifies the station that originated the packet. A Destination Address can specify either an "individual address" destined for a single station, or a "multicast address" destined for a group of stations. A Destination Address of all 1 bits refers to all stations on the LAN and is called a "broadcast address." |
| Type | Ether type |
| Data and padding | This field contains the data transferred from the source station to the destination station or stations. The maximum size of this field is 1500 bytes. A minimum size Ethernet packet is 64 bytes from the Destination Address field through the Frame Check Sequence. If the packet size of this field is less than 46 bytes, padding is used to bring the packet size up to the minimum length. |
| Frame check sequence | This field contains a 4-byte cyclical redundancy check (CRC) value used for error checking. When a source station assembles a packet, it performs a CRC calculation on all the bits in the packet from the Destination Address through the pad fields (that is, all fields except the preamble, start frame delimiter, and Frame Check Sequence). The source station stores the value in this field and transmits it as part of the packet. When the destination station receives the packet, it performs an identical check. If the calculated value does not match the value in this field, the destination station assumes that an error has occurred during transmission and discards the packet. |
為了實(shí)現(xiàn)互操作性，用戶需要注意TDMoP報(bào)頭的兩個部分：
UDP/IPv4報(bào)頭互操作性
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