分享
 
 
 

RFC1483ATM上的多协议封装

王朝other·作者佚名  2008-05-31
窄屏简体版  字體: |||超大  

rfc1483

PRess here to go to the top of the rfc 'tree'.

Network Working GroupJuha Heinanen

Reguest for Comments: 1483Telecom Finland

July 1993

Multiprotocol Encapsulation over ATM Adaptation Layer 5

Status of this Memo

This RFC specifies an IAB standards track protocol for the Internet community, and requests discussion and suggestions for improvements.

Please refer to the current edition of the IAB Official Protocol Standards for the standardization state and status of this protocol.

Distribution of this memo is unlimited.

Abstract

This memo describes two encapsulations methods for carrying network interconnect traffic over ATM AAL5.The first method allows

multiplexing of multiple protocols over a single ATM virtual circuit whereas the second method assumes that each protocol is carried over

a separate ATM virtual circuit.

1.IntrodUCtion

Asynchronous Transfer Mode (ATM) based networks are of increasing interest for both local and wide area applications.This memo

describes two different methods for carrying connectionless network

interconnect traffic, routed and bridged Protocol Data Units (PDUs),over an ATM network.The first method allows multiplexing of

multiple protocols over a single ATM virtual circuit.The protocol

of a carried PDU is identified by prefixing the PDU by an IEEE 802.2

Logical Link Control (LLC) header.This method is in the following called LLC Encapsulation and a subset of it has been earlier

defined for SMDS [1].The second method does higher-layer protocol multiplexing implicitly by ATM Virtual Circuits (VCs).It is in the

following called VC Based Multiplexing.

ATM is a cell based transfer mode that requires variable length user information to be segmented and reassembled to/from short, fixed

length cells.This memo doesn't specify a new Segmentation And Reassembly (SAR) method for bridged and routed PDUs.Instead, the

PDUs are carried in the Payload field of Common Part Convergence Sublayer (CPCS) PDU of ATM Adaptation Layer type 5 (AAL5) [2].Note that this memo only describes how routed and bridged PDUs are

carried directly over the CPCS of AAL5, i.e., when the Service Specific Convergence Sublayer (SSCS) of AAL5 is empty.If Frame RFC 1483Multiprotocol over AAL5July 1993 Relay Service Specific Convergence Sublayer (FR-SSCS), as defined in I.36x.1 [3], is used over the CPCS of AAL5, then routed and bridged PDUs are carried using the NLPID multiplexing method described in RFC

1294 [4].Appendix A (which is for information only) shows the format of the FR-SSCS-PDU as well as how IP and CLNP PDUs are encapsulated over FR-SSCS according to RFC 1294.

2.Selection of the Multiplexing Method It is envisioned that VC Based Multiplexing will be dominant in environments where dynamic creation of large numbers of ATM VCs is fast and economical.These conditions are likely to first prevail in

private ATM networks.LLC Encapsulation,

on the other hand, may be desirable when it is not practical for one reason or another to have

a separate VC for each carried protocol.This is the case, for example, if the ATM network only supports (semi) Permanent Virtual Circuits (PVCs) or if charging depends heavily on the number of

simultaneous VCs.When two ATM stations wish to exchange connectionless network

interconnect traffic, selection of the multiplexing method is done either by manual configuration (in case of PVCs) or by B-ISDN

signalling procedures (in case of Switched VCs).The details of B-ISDN signalling are still under study in CCITT [5].It can, however,

be assumed that B-ISDN signalling messages include a Low layer compatibility information element, which will allow negotiation of

AAL5 and the carried (encapsulation) protocol.

3.AAL5 Frame Format

No matter which multiplexing method is selected, routed and bridged PDUs shall be encapsulated within the Payload field of AAL5 CPCS-PDU.The format of the AAL5 CPCS-PDU is given below:

Heinanen[Page 2]

RFC 1483Multiprotocol over AAL5July 1993

AAL5 CPCS-PDU Format

The Payload field contains user information up to 2^16 - 1 octets. The PAD field pads the CPCS-PDU to fit exactly into the ATM cells such that the last 48 octet cell payload created by the SAR sublayer will have the CPCS-PDU Trailer right justified in the cell.The CPCS-UU (User-to-User indication) field is used to transparently transfer CPCS user to user information.The field has no function under the multiprotocol ATM encapsulation described in this memo and can be set to any value.The CPI (Common Part Indicator) field alings the CPCS-PDU trailer to

The Payload field contains user information up to 2^16 - 1 octets. The PAD field pads the CPCS-PDU to fit exactly into the ATM cells such that the last 48 octet cell payload created by the SAR sublayer will have the CPCS-PDU Trailer right justified in the cell. The CPCS-UU (User-to-User indication) field is used to transparently transfer CPCS user to user information.The field has no function under the multiprotocol ATM encapsulation described in this memo and can be set to any value.

 
 
 
免责声明:本文为网络用户发布,其观点仅代表作者个人观点,与本站无关,本站仅提供信息存储服务。文中陈述内容未经本站证实,其真实性、完整性、及时性本站不作任何保证或承诺,请读者仅作参考,并请自行核实相关内容。
2023年上半年GDP全球前十五强
 百态   2023-10-24
美众议院议长启动对拜登的弹劾调查
 百态   2023-09-13
上海、济南、武汉等多地出现不明坠落物
 探索   2023-09-06
印度或要将国名改为“巴拉特”
 百态   2023-09-06
男子为女友送行,买票不登机被捕
 百态   2023-08-20
手机地震预警功能怎么开?
 干货   2023-08-06
女子4年卖2套房花700多万做美容:不但没变美脸,面部还出现变形
 百态   2023-08-04
住户一楼被水淹 还冲来8头猪
 百态   2023-07-31
女子体内爬出大量瓜子状活虫
 百态   2023-07-25
地球连续35年收到神秘规律性信号,网友:不要回答!
 探索   2023-07-21
全球镓价格本周大涨27%
 探索   2023-07-09
钱都流向了那些不缺钱的人,苦都留给了能吃苦的人
 探索   2023-07-02
倩女手游刀客魅者强控制(强混乱强眩晕强睡眠)和对应控制抗性的关系
 百态   2020-08-20
美国5月9日最新疫情:美国确诊人数突破131万
 百态   2020-05-09
荷兰政府宣布将集体辞职
 干货   2020-04-30
倩女幽魂手游师徒任务情义春秋猜成语答案逍遥观:鹏程万里
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案神机营:射石饮羽
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案昆仑山:拔刀相助
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案天工阁:鬼斧神工
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案丝路古道:单枪匹马
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案镇郊荒野:与虎谋皮
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案镇郊荒野:李代桃僵
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案镇郊荒野:指鹿为马
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案金陵:小鸟依人
 干货   2019-11-12
倩女幽魂手游师徒任务情义春秋猜成语答案金陵:千金买邻
 干货   2019-11-12
 
推荐阅读
 
 
 
>>返回首頁<<
 
靜靜地坐在廢墟上,四周的荒凉一望無際,忽然覺得,淒涼也很美
© 2005- 王朝網路 版權所有