3
4
5
6
7
8
Decisions include how many
9
VLANs exist in a switch block
10
and where these devices are placed.
30
Layer 2 End-to-End VLAN Switched Ethernet Wiring Closet
Network Layer
192.20.21.0 192.20.24.0 192.30.20.0
Data-Link Layer Broadcast Domains
Engineering VLAN
Marketing VLAN
Sales VLAN
Physical Layer LAN Switch
Human Layer
VLAN1 VLAN2 VLAN3
Port-Driven
Floor #1
Floor #2
Floor #3
28
VLANs Establish Broadcast Domains
Broadcast Domain 2 Brong the Switch Block with
VLANs
1
2
Server Block
Core
上睑下垂
– 诊断:
• 临床表现 • 上睑缘与角膜相对位置 • 第一眼位睑裂高度 • 提上睑肌肌力判定
– 治疗:
• 先天性:手术,防弱视 • 后天性:病因治疗
睑缘炎
鳞屑性
病因 腺体分泌旺盛
涩感
有
充血,肿胀 有
溃疡
无
分泌物 腊样,鳞屑状
睫毛 脱落可再生