如何實(shí)現DS34S132與其它TDMoP器件的互操作
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互操作性是一個(gè)系統經(jīng)過(guò)很少甚至無(wú)需系統操作員介入而實(shí)現與其它系統協(xié)同工作的能力。系統的互操作性使其有可能為其它系統提供服務(wù)或接受其它系統的服務(wù),使得不同廠(chǎng)商的系統能夠協(xié)同工作。本應用筆記介紹如何設置DS34S132 TDM-over-Packet (TDMoP) IC，使其與其它TDMoP器件實(shí)現互操作。
引言
毋庸諱言，當今的通信系統需要不同設備和設備之間的復雜交互。隨著(zhù)技術(shù)的進(jìn)步，互操作性也變得更加重要?；ゲ僮餍允且粋€(gè)系統經(jīng)過(guò)很少甚至無(wú)需系統操作員介入而實(shí)現與其它系統協(xié)同工作的能力。系統的互操作性使其有可能為其它系統提供服務(wù)或接受其它系統的服務(wù)，從而使不同廠(chǎng)商的系統能夠協(xié)同工作。
本應用筆記著(zhù)重介紹Maxim TDM-over-Packet (TDMoP) IC，DS34S132。文章介紹了在DS34S132與其他廠(chǎng)商TDMoP器件之間實(shí)現互操作性的設置要求。
互操作性要求
Maxim的TDMoP器件產(chǎn)生的數據包與其他廠(chǎng)商的TDMoP器件的報頭信息可能不同。為了使TDMoP器件實(shí)現互操作，用戶(hù)需要了解器件的設置類(lèi)型。Maxim器件的設置為以下之一：
- IP/UDP/RTP/SAToP
- IP/UDP/RTP/CESoPSN
- MEF/RTP/CESoETH—非結構化(即MEF/SAToP)
- MEF/RTP/CESoETH—結構化鎖定(即MEF/CESoPSN)
- MPLS/RTP/SAToP—非結構化(即MPLS/RTP/SAToP)
- MPLS/RTP/CESoPSN—結構化鎖定(即MPLS/RTP/CESoPSN)
每種TDMoP器件設置都有不同的報頭。為了實(shí)現互操作性，必須將來(lái)自于Maxim TDMoP器件的報頭格式化，使其與其它器件的報頭相同。這意味著(zhù)用戶(hù)需要比較TDMoP器件的報頭，并查找格式差異。本應用筆記介紹如何利用Maxim的應用程序修改DS34S132 TDMoP器件的報頭。文章還介紹了如何修改Maxim綁定配置，以接受協(xié)議相同但報頭信息不同的數據包。
TDMoP格式
本節介紹TDM-over-Packet模塊的功能描述。為了通過(guò)分組交換網(wǎng)絡(luò )傳輸TDM數據，TDMoP器件將TDM數據封裝為以太網(wǎng)數據包，如圖1所示。TDMoP報頭不同數據塊的說(shuō)明請參見(jiàn)表1。
圖1. 以太網(wǎng)數據包格式的TDMoP封裝。
表1. 以太網(wǎng)數據包結構
| 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)現互操作性，用戶(hù)需要注意TDMoP報頭的兩個(gè)部分：
UDP/IPv4報頭互操作性
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