T1与E1网络基础知识详解

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"本文介绍了T1和E1网络的基础知识,包括T线路的原理、TDM技术、T线路的级别划分以及与之相关的DS0至DS4标准数字服务速率。" 在计算机网络中,T1和E1是两种广泛用于语音和数据传输的数字通信标准,尤其适用于电话系统和广域网(WAN)连接。它们是基于时分复用(TDM)技术的,允许在单一物理线路中同时传输多个独立的信号。 TDM是一种复用技术,它将多个较低带宽的信号合并成一个更高带宽的信号,以便在单个信道上传输。在T线路中,不同业务链路的时间段被分配给各个用户轮流使用,这样可以有效地利用有限的物理线路资源。当业务流量不大时,TDM对非实时应用如数据传输和文件浏览影响较小,节省了用户的成本。 T1和E1都是专用线路,需要预先向网络服务提供商申请。T1主要在美国和加拿大使用,提供1.544 Mbps的数据速率,由24个64 Kbps的DS0信道组成。E1则在欧洲和许多其他国家普遍采用,提供2.048 Mbps的数据速率,包含32个DS0信道。这些DS0信道可以承载语音通话、数据传输或其他通信服务。 T线路有级别的划分,包括T1、T2、T3等,这些级别基于DS0的速率进行复用。DS0是基本单元,其速率是64 Kbps,相当于ISDN的基本信道速率。DS1(T1)、DS2、DS3(也称为T3)和DS4等更高级别的速率则对应于更高的带宽需求。值得注意的是,T线路的级别划分在欧洲标准和国际标准中有所不同,具体体现在复用方式和命名上。 T1和E1技术在提供高效、经济的通信解决方案方面发挥着关键作用,特别是在需要多通道连接的场景下,如企业内部网络连接、远程办公站点之间的通信以及电话系统的集成。随着网络技术的发展,虽然现代网络更倾向于使用IP协议和更高级别的传输技术,但T1和E1仍然在很多现有的网络基础设施中占据一席之地。

select * from (select t1.[id] as t1_id,t1.[requestId] as t1_requestId,t1.[htqsrq] as t1_htqsrq,t1.[htjzrq] as t1_htjzrq,t1.[htbh] as t1_htbh,t1.[gf] as t1_gf,t1.[xf] as t1_xf,t1.[rq] as t1_rq,t1.[fkfs] as t1_fkfs,t1.[formmodeid] as t1_formmodeid,t1.[modedatacreater] as t1_modedatacreater,t1.[modedatacreatertype] as t1_modedatacreatertype,t1.[modedatacreatedate] as t1_modedatacreatedate,t1.[modedatacreatetime] as t1_modedatacreatetime,t1.[modedatamodifier] as t1_modedatamodifier,t1.[modedatamodifydatetime] as t1_modedatamodifydatetime,t1.[form_biz_id] as t1_form_biz_id,t1.[MODEUUID] as t1_MODEUUID,t1.[htfj] as t1_htfj,t1.[zje] as t1_zje,t1.[ds] as t1_ds,t1.[zjedx] as t1_zjedx,t1.[cspp] as t1_cspp,t1.[yfk] as t1_yfk,t1.[gxid] as t1_gxid,t1.[bz] as t1_bz,t1.[gfqymc] as t1_gfqymc,t1.[gfjc] as t1_gfjc,t1.[bh] as t1_bh,t1.[jylx] as t1_jylx,t1.[cght] as t1_cght,t1.[yf] as t1_yf,t1.[yfk1] as t1_yfk1,t1.[yf11] as t1_yf11,t1.[nf] as t1_nf,t1.[rksj] as t1_rksj,t1.[cclx] as t1_cclx,t1.[cgbt] as t1_cgbt,t1.[yfk2] as t1_yfk2,t1.[sywf] as t1_sywf,t1.[yfbl] as t1_yfbl,t1.[fhbl] as t1_fhbl,t1.[yfh] as t1_yfh,t1.[sykf] as t1_sykf,t1.[hzsdlqys] as t1_hzsdlqys,t1.[sys_workflowid] as t1_sys_workflowid,t1.[cgqzyz] as t1_cgqzyz,t1.[htwjpdf] as t1_htwjpdf,t1.[cghtlc] as t1_cghtlc,t1.[htzt] as t1_htzt,t1.[qzfs] as t1_qzfs,t1.[htwjtp] as t1_htwjtp,t1.[cgqzlc] as t1_cgqzlc,t1.[sjfk] as t1_sjfk,t1.[ydkds] as t1_ydkds,t1.[chpt] as t1_chpt,t1.[lxdhchr] as t1_lxdhchr,t1.[gxsjkx] as t1_gxsjkx,t1.[hkzt] as t1_hkzt,t1.[lcfkd] as t1_lcfkd,t1.[fkzlcid] as t1_fkzlcid,t1.[mode_top_4] as t1_mode_top_4,t1.[cgdj] as t1_cgdj,t1.[mode_top_22] as t1_mode_top_22,t2.[id] as t2_id,t2.[mainid] as t2_mainid,t2.[sld] as t2_sld,t2.[ppcj] as t2_ppcj,t2.[hsdj] as t2_hsdj,t2.[bz] as t2_bz,t2.[je] as t2_je,t2.[xhggyt] as t2_xhggyt,t2.[mxgxid] as t2_mxgxid,t2.[dqkckc] as t2_dqkckc,t2.[rkhkc] as t2_rkhkc,t2.[yf] as t2_yf,t2.[yldjbhyf] as t2_yldjbhyf,SELECT year(rksj) as 年 FROM uf_gfht as cus_年年 from uf_gfht t1 INNER join uf_gfht_dt1 t2 on t1.id = t2.mainid) tmp1 where t1 错在哪里

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