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電信網路的難題
• 規格不一(T-Carrier/E-Carrier/SDH...)
• 多種協定架構(ATM/Frame Relay/ISDN...)
• 管理困難• 查修及維護困難度高,需大量人力• 需要同步信號
2
PSTN TopologyIP
IP Phone
IP
IP Phone
User
Service
Routing
PSTN
3
PSTN Protocols Stack
Internet
Coxal Cabling
SDH
ATM TDM
DSL POTSLeaseLine
A/VServices
IP
VPN
Dialup
IPTVServices
NetworkServices
VoIPServices
Optical CablingWireless Cabling
PrivateNet
4
SDH Add Drop Mux
5
SONET/SDHADM-MSPP
6
T1 to E1 Translate
7
Carrier Frame SizeFrame Size Payload Speed Ratio
T1
T2
T3
E1
E2
E3
OC1/STM0
OC3/STM1
OC12/STM4
OC48/STM16
OC192/STM64
OC768/STM256
193 1536 1544 99.48%
1176 6144 6312 97.34%
4760 43008 44736 96.14%
240 1920 2048 93.75%
848 7680 8448 90.91%
1536 30720 34368 89.39%
6480 49536000 51840000 95.56%
19440 149760000 155520000 96.30%
77760 600768000 622080000 96.57%
311040 2404800000 2488320000 96.64%
1244160 9620928000 9953280000 96.66%
4976640 38485440000 39813120000 96.67%
8
Virtual Line
9
Ethernet Frame Format
Premble DA SA Type Payload FCS
1518 bytes
8 byte 6 byte 6 byte 2 byte 46-1500 byte 4 byte
Premble DA SA 0x8100 FCS
1522 bytes
8 byte 6 byte 6 byte 2 byte 46-1500 byte 4 byte
Type
2 byte
CoS PayloadVID
2 byte
Premble DA SA 0x88A8 FCS
1526 bytes
8 byte 6 byte 6 byte 2 byte 46-1500 byte 4 byte
Type
2 byte
CCoS Payload
CVID
2 byte
PCP/DES
VID
2 byte
Premble DA SA0x88E7 FCS
1536 bytes
8 byte 46-1500 byte 4 byte
Type
2 byte
CCoS Payload
CVID
2 byte
SCoSB-DA B-SA
6 byte 6 byte
0x88A8 I-SID
2 byte
Ethernet II Frame
CFI
0x8100
2 byte
CFI
0x8100
2 byte
CFI
CFI
BCoS
BVID
CFI
2 byte 2 byte 2 byte 3 byte 6 byte 6 byte
Premble DA SA Length Payload FCS
1518 bytes
7 byte 6 byte 6 byte 2 byte 46-1500 byte 4 byte
SFD
10
Ethernet Frame Evolution
Payload
SA
DA
Payload
VID
SA
DA
Payload
S-VID
SA
DA
C-VID
Payload
S-VID
SA
DA
C-VID
B-VID
B-SA
B-DA
I-SID802.3 802.1Q 802.1ad
802.1ah
Provider backbone bridges
Provider bridgesVirtual LAN
SA: Source MAC addressDA: Destination MAC addressVID: VLAN IDC-VID: Customer VIDS-VID: Service VIDI-SID: Service IDB-VID: Backbone VIDB-DA: Backbone DAB-SA: Backbone SA
11
Frame Semantic
• VLAN Cross Connect identifier has local port scope
• Frame format as defined in IEEE 802.1Q
• VLAN Cross Connect tagged frame allows up to 4K VLANs per port
Destination MAC Source MAC TPID Ether Type / Len Data FCSTCI
PCPCFI
VXC ID12-bit VLAN Cross Connect IDup to 4K VLANs per port
VXC-TAG
12
Service Model
• At the boundary of the VLAN-XC domain, the VLAN ID of the outer tag (C-tag or S-Tag) can be used to associate the frame with a particular VLAN-XC connection.
• If required, the outer tag (C-tag or S-tag) is preserved and transparently transported within the VLAN-XC domain
Destination MAC Source MAC Ether Type / Len Data FCSC-tag
Destination MAC Source MAC Ether Type / Len Data FCSS-tag C-tag
13
• Extended VLAN Cross Connect
• Frame Format as defined in IEEE 802.1ad
• VLAN Cross Connect tagged frame allows up to 16M VLANs per port
Frame Semantic
Destination MAC Source MAC TPID Ether Type / Len Data FCSTCI
PCPCFI
VLAN ID
TPID TCI
PCPCFI
VLAN ID
EVXC ID24-bit VLAN Cross Connect ID
up to 16M VLANs per Port
EVXC-TAG
14
VLAN Cross Connect with CE-VLAN Preservation Example
Destination MAC
Source MAC
CE-VLAN
Destination MAC
Source MAC
VXC=1024
CE-VLAN
Destination MAC
Source MAC
VXC=236
CE-VLAN
Destination MAC
Source MAC
VXC=2636
CE-VLAN
Destination MAC
Source MAC
CE-VLAN
L2
Frame
L2
Frame
L2
Frame
L2
Frame
L2
Frame
VLAN Cross Connect Connection
PE-Node PE-NodeP-NodeP-Node
Port 6Port 3 Port 2 Port 8 Port 4 Port 12 Port 6 Port 9
15
Extended VLAN Cross Connect Example
Destination MAC
Source MAC
CE-VLAN
Destination MAC
Source MAC
EVXC=12045
CE-VLAN
Destination MAC
Source MAC
EVXC=645
CE-VLAN
Destination MAC
Source MAC
VXC=15320
CE-VLAN
Destination MAC
Source MAC
CE-VLAN
L2
Frame
L2
Frame
L2
Frame
L2
Frame
L2
Frame
VLAN Cross Connect Connection
PE-Node PE-NodeP-NodeP-Node
Port 6Port 3 Port 2 Port 8 Port 4 Port 12 Port 6 Port 9
16
Scalability
• VLAN Cross Connect can be naturally extended to work with hierarchical domains using tunneling
• Uses standard VLAN stacking
MACEVXCTag
MACEVXCTag
MACEVXCTag
MACEVXCTag
MACEVXCTag
EVXCTag
MACEVXCTag
EVXCTag
Level n+1
Level n Level n
17
Ethernet Jumbo Frame一般的 Ethernet Frame Size 是以資料長度 1500 bytes 加上 18 bytes 的表頭所組成的。不論是 10Mbps 或是 10Gbps 都因為相容需要,而使用相同的 MTU。會選擇使用 1500bytes 的長度是因為早期的 10Mbps 的 Ethernet 使用 CSMA/CD 及同軸電纜,傳輸錯誤率並不低,若傳輸有錯誤發生時,所需重送的資料量就比較大,而且大的 Frame Size 代表傳送及接收時,都需要大量的記憶體作為 Buffer。但以今日的記憶體及處理器,相對網路傳輸速度需求而言,是較低的價格,而且利用光纖傳輸的品質,比銅纜好很多,所以將 Frame Size 放大是可以預見的。在 Internet 2 (I2) 的骨幹網路上就已經測試使用 4KByte和9KByte 的Jumbo Frame 多年。
而且其他非Ethernet的協定也都使用較大的Frame Size,若Ethernet也使用較大的Frame Size可以減少封包的切割,並可加快傳輸速度。
18
Media Type Speed Frame MTU Maximum Frame Length
Ethernet 10 Mbps 1500 1518
802.3 10 Mbps 1518 1536
802.3u 100 Mbps 1518 1536
802.3z/ab 1 Gbps 1518 1536
802.3ae/an 10 Gbps 1518 1536
802.3ba 100 Gbps 1518? 1536?
802.5 4 Mbps 4528 4550
802.5 16 Mbps 18173 18200
802.5 100 Mbps 18173 18200
802.11g 54 Mbps 2312 2346
FDDI 100 Mbps 4352 4470
Fiber Channel 2 Gbps 65280 65280
POS/OC48 2.5 Gbps 9180 9180
ATM/AAL5 9180 9180
Standard Frame Size
19
Jumbo Frame Benefit
• Lower Overhead of Packets
• High Utilization of Connection
• High Transmission Rate
• Low CPU Utilization
• Improved Performance of Transmission
20
Jumbo Frame Requirement
• Low Transport Error Rates
• High Speed Connection
• Hardware Buffer Size Limitation
• Long Size of Packet Aware
21
Jumbo Frame Problem
• Conjunction occur problem
• Short Size Packets
• Transmission Error problem
• Difficult to QoS
• Large Hardware Buffer
• Longer Delay
22
Ethernet Jumbo Frame
1.5K Frame = 1500 * 8 + 368 = 12368 bit4K Frame = 4000 * 8 = 32000 +368 bit9K Frame = 9000 * 8 = 72000 +368 bit16K Frame = 16000 * 8 = 128000 +368 bit32K Frame = 32000 * 8 = 256000 +368 bit64K Frame = 64000 * 8 = 512000 +368 bit
FrameSize (in bit)=IFG+SFD+DMAC+SMAC+Q+Q+Length+Payload+FCS=(96/8)+8+6+6+4+4+2+Payload+4=46+Payload=368+(Payload*8)
23
Frame Speed
Frame Size Ratio 10Mb10Mb 100Mb100Mb 1Gb1Gb 10Gb10Gb 100Gb100Gb
Frame/Sec Throughput Frame/Sec Throughput Frame/Sec Throughput Frame/Sec Throughput Frame/Sec Throughput
0.046K
1.5K
4K
9K
16K
32K
64K
736 50.00% 13587 5000000 135870 50000000 1358696 500000000 13586957 5000000000 135869565 50000000000
12368 97.02% 809 9702458 8085 97024580 80854 970245796 808538 9702457956 8085382 97024579560
32368 98.86% 309 9886307 3089 98863075 30895 988630746 308947 9886307464 3089471 98863074642
72368 99.49% 138 9949149 1382 99491488 13818 994914880 138183 9949148795 1381826 99491487950
128368 99.71% 78 9971332 779 99713324 7790 997133242 77901 9971332419 779010 99713324193
256368 99.86% 39 9985646 390 99856456 3901 998564563 39006 9985645634 390064 99856456344
512368 99.93% 20 9992818 195 99928177 1952 999281766 19517 9992817662 195172 99928176623
24
因為現在的 CPU大都使用中斷方式,處理因正常處理程序執行之外發生的事件,利用中斷可以有效的處理在相同的時間,發生事件而引發需執行的不同程序。假設網路處理單元需要 1000 個 CPU clock cycle 處理一個中斷服務,而中斷可以占用所有計算資源的一半。
當10Mb ethernet 使用最大為1500 byte 的 Frame size,最多產生每秒 810 個中斷,所以至少需要的處理速度為 1.6MHz。 810x1000x2=1620000=1.6MHz
而以10Gb Ethernet 而言,使用 1500byte Frame 就需要 1.6GHz。 808538x1000x2= 1617076000=1.6GHz.
若是使用 64Kbyte Frame 的話卻只需要 39MHz。 19517x1000x2=39034000Hz=39MHz.
若是 100Gb ethernet 使用 1500byte Frame 的話需要 16GHz。 8085382x1000x2=16170764000=16GHz.
但換成 64Kbyte Frame 只需要 390MHz。 195172x1000x2=390344000=390.34MHz
這樣使得使用較低階的 CPU 傳送全速 100Gb 的資料成為可能。
25
但是為何 Jumbo Frame 沒有全面取代原本的1500byte 的 Ethernet frame size ?
原因除了要向前版相容,以免因換用 Jumbo Frame 而需要將全部的網路設備更換。還有就是因為換了較大的 Frame Size 而造成 Buffer 變小,而有可能原本更換為 Jumbo Frame 是要加快傳輸速度,結果可能因為 Buffer 變小而反而變慢。
但為何 Line Speed 的 Switch 需要使用到 Buffer ?
事實上因為在 Switch 時會需要查 Forwarding Table 及對 Frame 作一些錯誤防止的處理,所以利用內部的 Buffer 先將資料暫存,等到檢查無誤之後,再傳送。或者是因為 QoS 的考慮,而需要將具有高優先的資料先行傳送,而低優先的資料,就只有先暫存在 Buffer 中了。
26
例如原本使用 1500byte 時,網路設備的 Buffer 最多可以暫存256個 Frame 的資料。 1500x256=384000=384KByte ,而以一部 24 port 的 Lan switch 來說也只要 384x24=9216=9.216MByte 的空間就可以了,換成每片4Mbit 的晶片,三片就可以工作得很好。這樣的空間可以處理10Mbit Ethernet大約一秒的 delay。但是換成 4K Jumbo Frame 時就只有 384000/4000=96個 Frame,而換成 9K Frame 只有 384000/9000=42個Frame,而 16K Frame 只有 384000/16000=24個 Frame。
以原本的設計,因 QoS 設計,區分為 4 個等級時,每個 Queue 還可以放 256/4=64 個 Frame ,這樣子在 QoS 的調整上還足以應付需求。 若為 9K Frame 時,每個 Queue 只可以放 10 個 Frame 的資料,而 16K Frame 更只有24/4=6 個,這樣 Buffer 很容易就會滿了,而發生資料遺失。所以要使用 Jumbo Frame 時,在設計 QoS 時需要注意到這些細節作調整。
27
Line Protection
28
STP Multiple Path Protection
29
Ring Protection
30
RPR Station Structure
31
RPR Architecture
32
RPR Operation
Failure Bandwidth Allocation
33
ITU-T G.8032 Topology
34
Line Protection Summary
反應時間 頻寬效率 架構 硬體需求
STP >50ms 一般 Loop None
RPR <50ms 高 Ring Need
ERPS <50ms 一般 Loop None
35
OAM Standards
• IEEE standards 802.3ah EFM OAM for access link
• IEEE standards 802.1ag CFM - Connectivity Fault Management on link layer
• ITU Y.1730 / Y1731 Ethernet OAM
• MPLS OAM
• MEF-16 OAM
36
Fault Fault Detection
Fault Notification
Fault Verification
Fault Isolation Repair Repair
Verification
Link
ServiceTransportService
Transport
ServiceLevel
Agreement
802.3ahEFM OAM SNMP
802.3ahEFM OAM
802.3ahEFM OAM RSTP
802.3ahEFM OAM
IEEE 802.1ag CFM / ITU-T Y.1731IEEE 802.1ag CFM / ITU-T Y.1731IEEE 802.1ag CFM / ITU-T Y.1731IEEE 802.1ag CFM / ITU-T Y.1731 MSTP802.1agY.1731
MPLS VCCD/BFDMPLS VCCD/BFDMPLS VCCD/BFDMPLS VCCD/BFD MSTP LSP Ping
MEF Service OAMMEF Service OAMMEF Service OAMMEF Service OAM MEF
OAM Protocol Matrix
37
Access CustomerAccessCoreCustomer
Service Provider
802.3ah802.3ah
End to End OAM
802.1ag
802.1ag 802.1ag 802.1ag
CE CEU-PE U-PE
OperatorDomain
OperatorDomain
OperatorDomain
OAM in networks
38
IEEE 802.3ah OAM
• Define in IEEE 802.3ah Ethernet First Mile section 57.
• Use MAC sublayer multicast slow protocol
• Monitor link operation
• Remote fault indication
• Remote loopback control
39
OAM functions
• Auto discovery
• Unidirectional fault signaling
• Remote loopback test
• Link monitoring
• Critical Events
• Layer 2 variable retrieval
• Organization specific extensions
40
OAM Sublayer Block
Multiplexer Parser
Control
MAC Data request MAC Data Indication
MAC Data IndicationMAC Data request
OAM requestLoopback Frame
CTRL OAM request CTRL OAM Indication
OAM CTRLRequest
OAM CTRLIndication
OAM PDUIndication
OAM PDURequest
OAM Sublayer block diagrom
41
OAM Remote Loopback
Physical
MAC
MAC Control
OAM
OAMClient
MACClient
Physical
MAC
MAC Control
OAM
OAMClient
MACClient
Medium
LocalDTE
RemoteDTE
OAM Remote Loopback
42
IEEE 802.1ag CFM
• Continuity Check packet type
• Layer 2 Ping packet type
• Layer 2 Trace Route packet type
• Per services fault isolation with VLAN
• Uses domains to contain OAM flows and bound OAM responsibilities
43
ITU-T Y.1731
• Alarm Indication Signal (Eth-AIS)
• Remote Defect Indication (Eth-RDI)
• Locked Signal (Eth-LCK)
• Test Signal (Eth-TEST)
• Performance Monitoring (Eth-PM)
• Frame Loss Measurement (Eth-LM)
• Frame Delay Measurement (Eth-DM)
44
MPLS OAM
• Label Switched Path (LSP) Ping
• Label Switched Path (LSP) Traceroute
• Virtual Circuit Connection Verification (VCCV)
• Bi-directional Forwarding Detection (BFD)
• Fast Re-Route
45
MFE OAM
• Point to point Ethernet Virtual Circuit (EVC) Performance Monitoring (PM)
• Point to multi-point EVC PM
• Multi-point to multi-point EVC PM
• EVC Fault management
46
PWE3 Reference Model
CE1 PE1 CE2PE2
Emulated Service
PSN Tunnel
Pseudo Wire
Customer Edge 1 Customer Edge 2
Provider Edge 1 Provider Edge 2
PW1
PW2
Attachment Circuit Attachment Circuit
PWE3 reference model
Physical Link Physical LinkLogical Link
Reference Clock
47
Protocol Stack Reference ModelEmulated Service
TDM/ATM/FR/Ethernet
PayloadEncapsulation
PSN
PW Demultiplexer
PSN Tunnel
PSN
Physical Layers
Emulated ServiceTDM/ATM/FR/Ethernet
PayloadEncapsulation
PW Demultiplexer
PSN Tunnel
PSN
Physical Layers
PSN Tunnel
Pseudo Wire
Emulated Service
PWE3 Protocol Stack Reference Model
48
TDMoIP for UDP/IPIP Header
Length
Flags
IP TOS
Identification
IP Version Total Length
Fragment Offset
Time to Live Protocol IP Header Checksum
Source IP address
Destination Ip address
Source Port Number Destination Port Number
UDP ChecksumUDP Length
PT RTP Sequence Number
Timestamp
SSRC Identifier
Sequence Number
Adapted Payload
RTV P X CC M
RES L R M RES Length
TDMoIP Packet format for UDP/IP
RFC-5087
49
NS-2Simulation
50
Simulation Parameters
• 1.5/4/9/16Kbps Frame Size
• 10/100/1000/10000 Packets Queue Size
• 10Mbps for 64Kbps DS0
• 100Mbps for 1.544/2.048Mbps T1/E1
• 1Gbps for 44.736/34.68Mbps T3/E3
• 10Gbps for 155.52Mbps STM1
• 80% Bandwidth
51
Sim Throughput
52
53
54
55
56
57
58
Sim Delay
59
60
61
62
63
64
65
Sim Loss
66
67
68
69
70
71
72
Simulation Result
Connections
DS0 125
T1/E1 51/39
T3/E3 17/23
STM1 51各項測試表現以1000<Queue Size <10000 為最佳
80% DS0 in Structure DS0 Only
Performance
10Mbps 125 125 100%100Mbp
s1224/1170 1250 97.92%/93.6%
1Gbps 11424/11040 12500 91.4%/88.32%
10Gbps 102816 125000 82.26%
10Gbps Ethernet以80%頻寬傳輸125000 DS0,若是附加到STM1 Frame則只有102816 DS0,佔82.26%,而和總頻寬10Gbps相比為62.8%。這對9.95328Gbps的STM64的96.66%是較差,但是若將價格及管理花費,還有維護的方便等一起加進來考量,就不算太差。
73
Conclusion
74
PSTN v.s. Carrier Grade Ethernet
75
Next GenerationPSTN TopologyPOTS Phone POTS Phone
User
Service
Routing
Carrier Grade Ethernet
76
Carrier-Grade Ethernet
77
使用乙太網路作為基礎傳輸的好處
• 傳輸速度已達10Gbps,但價格卻是逐年下降。
• 傳輸距離可達數百公里。
• 可減化傳輸協定的層級。
• 可利用光纖Ethernet傳輸,錯誤率低,較銅線可靠穩定。
78
使用乙太網路作為基礎傳輸的好處
• 擴充性高
• 維護非常簡單
• 設備價格較低。• 使用單一架構,可簡化網路。• 架設、測試、維護簡單。• Overhead較少
79
使用乙太網路作為基礎傳輸的好處
• 乙太網路的連接已可從LAN至MAN而至WAN。
• 可利用VLAN作虛擬線路設定,並區分不同服務等級。
• 網路拓蹼可為環狀或樹狀架構或混合。
• 已支援OAM及時管理及監控。
80
Technology
• VLAN/VLAN stacking (IEEE 802.1Q/ad/ah)
• Extending the Spanning Tree concept (IEEE 802.1D/S/W)
• Resilient Packet Ring (IEEE 802.17)
• MPLS (ITU-T 8110.1/8112/8121)
• Ethernet OAM (IEEE 802.3ah/802.1ag/ITU-T Y.1731)
81
Protocol Layer FunctionalityScalability QoS/TE Resilience OAM
IP Subnet, NAT DSCP Re-Routing Ping, Trace route etc.
Ethernet VLAN Switching
12/24 bitLabel space
GMPLS-based TE,802.1p prioritization
1:1 protection switching
802.1ag
EthernetMAC-in-MAC
46,46+12 bitLabel space
GMPLS-based TE,802.1p prioritization
1:1 protection switching
802.1ag
EthernetT-MPLS
20 bitLabel space
GMPLS-based TE,Prioritization EXP bits
1:1 protection switching, Fast Re-Route
802.1ag,LSP ping/LSP traceroute
EthernetPHY
10/100/1000Mbps10/100Gbps
802.17 RPR 802.3ah
WDM DWDM Standby channels
Fiber bundles Redundant fibers
82
802.1Q VLAN
802.1ah MAC-in-MAC 802.3ah OAM
802.1ad Q-in-Q
802.1aq OAM
802.1ad Q-in-Q
802.3
802.1D/S/W STP/RSTP/MSTP
802.17 RPR
802.1Q VLAN
802.1Q VLAN
802.2
PWE3
IP
PWE3
T-Carrier/E-Carrier/SONET/SDH
Audio/Video/Data Services
MPLS
PSTN
VPLS
VoIP
Virtual Circuit
TCP/UDP
SNMP
1588 PTP
Ethernet Protocols Stack
83
The End
84