10回目イーサネット技術(3/4)

10回目イーサネット技術(3/4)
Frame Forwarding (1)
10回目イーサネット技術(3/4)
z
Ethernet Frame Forwarding
z
Broadcast & Select
z
z
z
VLAN
z
Link Aggregation
Shared Media ‐> Repeater HUB
Discard at PCs
Shared Medium
MAC
frame
A to D
×
○
×
PC -A
PC -D
PC -B
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PC -C
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Frame Forwarding (2)
z
Frame Forwarding (3)
MAC learning
z
Discard at output filter
z Unknown destination ‐> B & S
z
MAC learning + Switch
z
z
MAC
frame
Shared Medium
Unknown destination ‐> B & S
Known destination ‐> switch
Switch
FDB: Forwarding Database
×× × ×
A to D
A to D
A to D
B to C
○
PC -A
PC -A
PC -D
PC -B
PC -C
PC -D
PC -B
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z
48 bit
I/G bit (Individual/Group)
z
U/L bit (Unique/Local)
z
z
z
z
0: Unicast address, 1: Multicast address
z
z
0: Globally unique address (managed by IEEE)
1: Locally administered address
z
24 bits Vender assigned serial ID z
Win XP – ipconfig /all
Linux /sbin/ifconfig –a z
22 bits Organizationally Unique Identifier (OUI)
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Examples of the MAC address
z
z
PC -C
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MAC address format
z
MAC
frame
FDB
00‐1E‐65‐14‐69‐92 (00‐1E‐65 ‐> Intel)
http://standards.ieee.org/regauth/oui/oui.txt
01‐80‐C2‐00‐00‐02 (IEEE 802.3 std. Slow_Protocols_Multicast
address) (00‐80‐C2 ‐> IEEE 802.1 Committee)
z
z
OUI is defined as 24 bits ID (“00” + 22 bits)
z
On the wire
48 bits (6 Bytes)
This is a multicast address !!!
01‐00‐5E‐00‐00‐00 (Internet Multicast address) (00‐00‐5E ‐> Internet Assigned Numbers Authority: IANA)
This is a multicast address !!!
I/G U/L
I/G U/L
OUI 24 bits
1 0 0 0 0 0 0 0 00000001 01000011 00000000 00000000 01000000
In the memory (01-80-C2-00-00-02)
24 bits
222=4,194,304
U/L I/G
224=16,777,216
0 0 0 0 0 0 0 1 10000000 11000010 00000000 00000000 00000010
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1
Bit transmission
z
z
Half Duplex and Full Duplex (1)
Octet by Octet
LSB to MSB (except CRC 4 Octets)
z
Half Duplex
z Send or Receive
z 10 Mbps ‐> 1 bit = 0.1 μs
z
= 20m (in fiber 5ns/m)
1500 B = 12,000 bit = 240 km z Sending data is also received at sender PC
Ethernet Frame
Shared Medium
CRC protection
Extension
CRC
4 OCT
PAD
TYPE/
LEN.
DATA
0-1500 OCT
2 OCT
SA
DA
6 OCT
6 OCT
S
F
D
PREAMBLE
Inter Frame Gap (IFG)
8 OCT
A to D
Min. 12 OCT
×
MAC header
Frame Size
×
×
○
PC -A
Ethernet Packet
PC -D
PC -B
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PC -C
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Half Duplex and Full Duplex (2)
z
Forwarding Principle
z
Full Duplex
z Send and Receive
z
If Destination MAC is not found in FDB
z
If there is a loop, frames are exploded.
z
z Sending data and Receiving data are z
MAC learning
independent
Send 100 Mbps + Receive 100 Mbps = 200 Mbps throughput (Cisco Count)
Switch
z
z
Frame is broadcast to all ports except the incoming port.
Meltdown the network.
No Loop is allowed.
Switch
FDB
Switch
Switch
Switch
Switch
A to D
B to A
PC -A
PC -A
PC -D
PC -B
PC -D
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How to avoid a loop
Loopを作ると何が起きる
z
矢上の研究室内でイーサネットループを作成
z
STP (Spanning Tree Protocol)
z
z
自動的にITC管理のスイッチがポートを閉塞
z
外部への通信が不可能に
z
z
ループ解消後、ITCに電話連絡してポート閉
塞を解除して正常通信に移行
z
1985 DEC, IEEE802.1D‐1990
Loop is allowed in a physical network topology.
z Construct a tree topology in the logical network topology.
z
Switch
Logically shut down the some links. ll h d
h
l k
Switch
Switch
Switch
ループ実験は、ITCの運用時間中にやること
Switch
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Switch
Switch
Switch
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2
How to make a tree topology
z
Select “Root Bridge (RB)”
z
z
Bridge (switch) which has the smallest “Bridge ID(64bit)” is selected as RB.
z
z
Example (1)
If A is selected as RB
z A‐B = 10, A‐C‐B=35, A‐C‐D‐B=45
z A‐C=20, A‐B‐C=25, A‐B‐D‐C=35
16 bit priority (default 0x8000) + 48 bit MAC address
z A‐B‐D=25, A‐B‐C‐D=35, A‐C‐D=30
Each bridge calculate a shortest path to RB.
g
p
A port status which belongs to the shortest path route is set to “Forwarding”. z A port status which belongs to not the shortest path route to RB is set to “Blocking” z
A
B
cost = 10
○
A
B
× ×
cost = 20
cost = 15
cost = 15
○
C
cost = 10
D
C
×
×
○
×
D
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Example (2)
z
Example (3)
If B is selected as RB
z
If link B‐C is broken
z B‐A = 10, B‐C‐A=35, B‐D‐C‐A=45
z B‐A = 10, B‐D‐C‐A=45
z B‐C=15, B‐A‐C=30, B‐D‐C=25
z B‐A‐C=30, B‐D‐C=25
z B‐D=15, B‐A‐C‐D=40, B‐C‐D=25
A
cost = 10
B
A
z B‐D=15, B‐A‐C‐D=40
○
A
B
cost = 10
B
A
×
cost = 20
cost = 20
×
C
cost = 10
D
C
B
×
cost = 15
cost = 15
○
○
×
cost = 15
○
×
×
C
D
cost = 10
D
C
○
○
×
D
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Why port is closed with STP?
z
STP is worked on the ITC’s Switch. z
z
Blocking to Listening: Max Age 20 sec
z Listening to Learning: Forward Delay 15 sec
z Learning to Forwarding: Forward g
g
Delay 15 sec
z Total 50 sec for the standard STP.
z
STP frames (Bridge Protocol Data Unit: BPDU) are exchanged among ITC’s Switch and your lab’s switches.
But cheap switches (10/100M/1G) /HUBs do not support STP !!!
z
z
STP Timer Value
Ethernet Bridge constructed on PCs may not support STP.
z It is too slow for route repair.
Loop at such switches can not avoid with STP!!!
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STP to Rapid STP (RSTP)
IEEE802.1Q‐1988 VLAN
IEEE802.1w‐2001 (IEEE 802.1D‐2004)
Few seconds restoration.
z STP upper compatible.
z
z
Virtual LAN
z
Real LAN
Virtual LAN #100
Virtual LAN #297
Virtual LAN #652
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VLAN Tag Frame
z
Two types of VLAN (1/2)
Type=0x8100 IEEE802.1Q VLAN
z
Port VLAN
z 1 switching HUB is partitioned into +4 OCT
multiple switch segments.
VID Format (On the wire expression)
P l d
Payload
MAX Payload
1518B
type
VID
type
type
SA
DA
SA
DA
802.3
802.1Q
C-TAG
User
Priority
C
F
I
8
5
7
6
VID (12 bit)
4
3
2
1
8
7
6
Segment #1
5
4
3
2
1
User Priority : 3 bit
CFI : Canonical Format Indicator : 1 bit
0 for Ethernet (Little-Endianness)
1 for Token Ring (Big-Endianness)
Port #
1
2
Port #
11
12
VID : Virtual LAN Identifier
0 for null VLAN ID (use User Priority)
1 for default VLAN
4095 for switch management
9
13
10
20
Segment #2
86
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Two types of VLAN (2/2)
z
Tag VLAN utilization
z
Tag VLAN
z
Tagged Port and Untagged Port
z
A link (port) is shared by several VLANs.
z
z Each VLAN is distinguished with VID in C‐TAG.
Switch adds C‐TAG to the incoming frame
Switch removes C‐TAG of the outgoing frame No VID
VID 100
VID=100
Switch
VID 100
VID=100
Switch
Switch
VID=1022
Switch
VID=1022
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4
PC can handle VLAN tag
z
VLAN configuration on Linux
Ethernet NIC can support logical interface.
z
z
# /sbin/vconfig add eth0 1022
z
# /sbin/vconfig set_egress_map eth0.122 [sokcket_buffer_priority] 4
z
Ex. Eth0, Eth0.100, and Eth0.1022
z
z
Eth0 is untagged interface.
Eth0.100 and Eth0.1022 are tagged interface.
z
Eth0
Eth0.100
z
VID=1
VID=100
make eth0.1022
IP packets output from [socket_buffer_priority] are mapped with user priority value 4
mapped with user priority value 4.
# /sbin/vconfig set_ingress_map eth0.122 [sokcket_buffer_priority] 4
z
VID=1022
Ethernet frames input with user priority value 4 are queued to the [socket_buffer_priority] buffer.
Switch
Eth0.1022
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Linux GREtap
Link Aggregation (LAG) IEEE802.3ad‐2000
z
After kernel 2.6.30(?)
Ethernet over IP (GRE) tunnel
z
Physically 1 NIC, but logically many NISs is possible
z
z
z
z
# ip link add [name] type gretap local local.ip.address
remote remote.ip.address
Several links are aggregated into a logical big pipe link.
z
Two 1 Gbps links can be aggregated into one 2 Gbps link. z
z
virtualization
z
Full duplex links
All component links are the same speed.
p
Flow bandwidth can not over the component link bandwidth. Veth0
Veth0
Link Aggregation (x2)
IP network
Veth1
131.232.56.10
123.4.5.6
Veth2
Switch
Switch
Link Aggregation (x3)
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234.56.78.9
まとめ
z
Ethernet Frame Forwarding
【8】 11月15日 イーサネット技術(1)
【9】 11月29日 イーサネット技術(2)
【10】 12月6日 イーサネット技術(3)
3
【11】 12月13日イーサネット技術(4)
【12】 12月20日フォトニックネットワーク(1)
【13】 12月27日 フォトニックネットワーク(2)
【14】 1月17日 フォトニックネットワーク(3)
レポート〆切(予定) 1月24日(木)
MAC address learning + broadcast
z Loop operation is not allowed
z Spanning Tree Protocol (STP) is used to prevent the loop operation.
Virtual LAN
i
l A
z
z
4094 virtual LANs can be mapped on the physical LAN. Link Aggregation
z
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スケジュール
z
z
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Logical big pipe can be made by aggregation.
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5
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