求大神回答EPL和EVPL的区别，986题库里面的疑问

edward_cheung

事件是由于986的题库里有两个很相似的题，令我疑惑了，题目如下：
8 O" f) i( G2 o6 t% F% i  q( u第一题：QUESTION 142
% z" j1 P: M4 k5 l2 q5 X. L$ yWhich two statements are true about an EPL? (Choose two.)
3 x, o  b& W1 l+ @7 Q$ A* XA. It is a point-to-point Ethernet connection between a pair of NNIs.
B. It allows for service multiplexing.
1 L1 @; f1 g6 K2 x0 w4 K9 VC. It has a high degree of transparency.
$ z& n; {! A, I, fD. The EPL service is also referred to as E-line.
6 L+ J7 J+ u. f! F; V2 R+ _Answer: CD            这里的答复说选CD，但是我查了资料，说EPL是点对点透传，为啥不选A？？
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' W- o3 Y: v" C: ~第二题：QUESTION 155
Which two statements are true about an EVPL? (Choose two.)
# ?) w( m+ X- x0 p  D9 Z2 s5 m7 VA. It has a high degree of transparency.
. B4 Z) S% i3 l/ D' o) YB. It does not allow for service multiplexing.
# D" P* F& e; K, H9 i+ j  RC. The EVPL service is also referred to as E-line.
- e6 O( ]5 I1 O- z! }D. It is a point-to-point Ethernet connection between a pair of UNIs.
Answer: CD             这里答案选CD，相对EPL来说EVPL这个就是多了V这个关键词，这里就选了P-T-P这个答案。
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5 X0 O, f& Z5 {* e, n有大神解释一下EPL和EVPL的区别吗？感谢大家

daniel@990.net

Wikipedia被封的恶果，谨摘录如下
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3 V1 F1 v% p' W" B% wEthernet private line (EPL) and Ethernet virtual private line (EVPL) are data services defined by the MEF. EPL provides a point-to-point Ethernet virtual connection (EVC) between a pair of dedicated user–network interfaces (UNIs), with a high degree of transparency. EVPL provides a point-to-point or point-to-multipoint connection between a pair of UNIs.

The services are categorized as an E-Line service type, with an expectation of low frame delay, frame delay variation and frame loss ratio. EPL is implemented using a point-to-point (EVC) with no Service Multiplexing at each UNI (physical interface), i.e., all service frames at the UNI are mapped to a single EVC (a.k.a. all-to-one bundling).

# L  d% B9 |- FDue to a high degree of transparency, EPL is often used to provide point-to-point Transparent LAN Service (TLS), where the service frame's header and payload are identical at both the source and destination UNI. Some implementations tunnel most Ethernet Layer 2 Control Protocols (L2CPs) except for some link layer L2CPs such as IEEE 802.3x pause frames.

9 F* ?1 k3 X6 T& V; \Unlike EPL, EVPL allows for service multiplexing, i.e., multiple EVCs or Ethernet services per UNI. The other difference between the EVPL and EPL is the degree of transparency - while EPL is highly transparent, filtering only the pause frames, EVPL is required to either peer or drop most of the Layer 2 Control Protocols.
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' j2 f, o+ Z' I* Z- H第一题的A就一个小错，是UNI之间的链接，而不是NNI。

4 g) Y" E" V+ w顺便说一句，MEF标准根本就是垃圾，实际工作中不用看。

edward_cheung

感谢上面大神回答，谢谢了
( V. B" p7 ]; A* Q; o4 MEPL provides a point-to-point Ethernet virtual connection (EVC) between a pair of dedicated user–network interfaces (UNIs), with a high degree of transparency
EVPL provides a point-to-point or point-to-multipoint connection between a pair of UNIs
8 Y. G0 q' J2 wUnlike EPL, EVPL allows for service multiplexing