Sem fio : Cisco ASR 5000 Series

Geração do pacote ICMP do 5000 Series ASR da identificação CLI e de fragmentação

18 Junho 2016 - Tradução por Computador
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Introdução

Este documento descrevem os contagens de byte relatados pelos comandos show port e o comando ping quando os sibilos estão executados no CLI na plataforma do 5000 Series do roteador dos serviços da agregação (ASR). Igualmente demonstra os efeitos da fragmentação quando os pacotes enviados são maiores do que a unidade de transmissão máxima configurada (MTU) na relação. Esta é boa informações de fundo a ter quando você pesquisa defeitos edições do plano de usuário com sibilo ou mesmo geralmente para os pacotes que passam através do chassi. Também, a experimentação com sibilos em um nó é uma grande maneira de confirmar os conceitos explicados neste documento.

Contribuído por Dave Damerjian, engenheiro de TAC da Cisco.

Problema

Quando você especifica o tamanho de um pacote do Internet Control Message Protocol (ICMP), o tamanho refere o payload cru que obtém envolvido acima no pacote. Não inclui o cabeçalho ICMP (8 bytes) OU o cabeçalho IP (20 bytes). Igualmente o notable é o cabeçalho de Ethernet (14 bytes = MAC de destino (6) + MAC de origem (6) + tipo de frame de Ethernet (2)), a etiqueta VLAN (4 bytes), e a sequência de verificação de frame da Ethernet de arrasto (FCS, 4 bytes), o mais atrasado de que não é ser indicada em um traço de Wireshark.

Solução

Quando você vir a saída do show port [npu | a ligação de dados] opõe o comando, a matemática que pode ser aplicada é mostrada neste exemplo. Combine as cores a fim obter uma compreensão direta. Este exercício trabalha em uma porta com o pouco ao sem tráfego enquanto permite que um sibilo seja enviado sem nenhum outro tráfego para se nublar a saída resultante.

Tamanho de virulência: 56 bytes (que é igualmente o padrão para este comando)

Payload + cabeçalho ICMP: 64

Encabeçamento do payload + do cabeçalho ICMP +IP: 84

Encabeçamento do payload + do cabeçalho ICMP +IP + cabeçalho de Ethernet + etiqueta VLAN: 102

Payload (56) + encabeçamento do cabeçalho ICMP (8) +IP (20) + cabeçalho de Ethernet (14) + etiqueta VLAN (4) + FCS (4): 106

  context Ctx
    interface 21/1 broadcast
      ip address 10.193.82.118 255.255.255.0
      ip mtu 1500
    #exit
 
  port ethernet 21/1
    no shutdown
    vlan 30
      no shutdown
      bind interface 21/1 Ctx
    #exit
  #exit
 
[Ctx]ASR5000> show ip arp

Flags codes:
I - Incomplete, R - Reachable, M - Permanent, S - Stale,
D - Delay,      P - Probe,     F - Failed

Address         Link Type Link Address      Flags  Mask            Interface
10.193.82.1     ether     00:00:0C:07:AC:1E R                      21/1

 
[Ctx]ASR5000> show ip route
 
"*" indicates the Best or Used route.  S indicates Stale.

 Destination         Nexthop          Protocol   Prec Cost Interface
*0.0.0.0/0           10.193.82.1      static     1    0    21/1
 
[Ctx]ASR5000> clear port data counters 21/1
Saturday April 12 14:06:21 UTC 2014

[Ctx]ASR5000> clear port npu count 21/1
Saturday April 12 14:06:21 UTC 2014

[Ctx]ASR5000> ping 10.193.82.1 count 1 size 56
Saturday April 12 14:06:21 UTC 2014
PING 10.193.82.1 (10.193.82.1) 56(84) bytes of data.
64 bytes from 10.193.82.1: icmp_seq=1 ttl=255 time=0.957 ms

--- 10.193.82.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.957/0.957/0.957/0.000 ms
 
Note that the datalink counters include the FCS bytes, while both datalink and npu
counters include the ethernet frame and vlan tags.

[Ctx]ASR5000> show port datalink count 21/1
Saturday April 12 14:06:25 UTC 2014
Counters for port 21/1:
Line Card  Gigabit Ethernet Port
Rx Counter                        Data  |  Tx Counter                       Data
-----------------------  -------------- + -----------------------  -------------
RX Unicast frames                   112 | TX Unicast frames                    1
RX Multicast frames                   3 | TX Multicast frames                  0
RX Broadcast frames                   9 | TX Broadcast frames                  0
RX Size   64 frames                   0 | TX Size   64 frames                  0
RX Size   65 ..  127 fr              14 | TX Size   65 ..  127 fr              1
RX Size  128 ..  255 fr               0 | TX Size  128 ..  255 fr              0
RX Size  256 ..  511 fr             110 | TX Size  256 ..  511 fr              0
RX Size  512 .. 1023 fr               0 | TX Size  512 .. 1023 fr              0
RX Size 1024 .. 1518 fr               0 | TX Size 1024 .. 1518 fr              0
RX Size > 1518 frames                 0 | TX Size > 1518 frames                0
RX Bytes OK                       43966 | TX Bytes OK                        106
RX Bytes BAD                          0 | TX Bytes BAD                         0
RX SHORT OK                           0 | TX PAUSE                             0
RX SHORT CRC                          0 | TX ERR                               0
RX OVF                                0 |
RX NORM CRC                           0 |
RX LONG OK                            0 |
RX LONG CRC                           0 |
RX PAUSE                              0 |
RX FALS CRS                           0 |
RX SYM ERR                            0 |
-----------------------  -------------- + -----------------------  -------------

[Ctx]ASR5000> show port npu count 21/1
Saturday April 12 14:06:25 UTC 2014
Counters for port 21/1
Counter                  Rx Frames       Rx Bytes      Tx Frames        Tx Bytes
-------------------- ------------- --------------- ------------- ---------------
Unicast                          1             102             1             102
Multicast                        3             202             0               0
Broadcast                        8             512             0               0
IPv4 unicast                     1             102             1             102
IPv4 non-unicast                 1              66             0               0
IPv6 unicast                     0               0             0               0
IPv6 non-unicast                 0               0             0               0
Fragments received               0               0           n/a             n/a
Packets reassembled              0               0           n/a             n/a
Fragments to kernel              0               0           n/a             n/a
HW error                         0               0           n/a             n/a
Port non-operational             0               0             0               0
SRC MAC is multicast             0               0           n/a             n/a
Unknown VLAN tag                 0               0           n/a             n/a
Other protocols                  2             136           n/a             n/a
Not IPv4                         0               0           n/a             n/a
Bad IPv4 header                  0               0           n/a             n/a
IPv4 MRU exceeded                0               0           n/a             n/a
TCP tiny fragment                0               0             0               0
No ACL match                     0               0             0               0
Filtered by ACL                  0               0             0               0
TTL expired                      0               0           n/a             n/a
Flow lookup twice                0               0           n/a             n/a
Unknown IPv4 class               0               0           n/a             n/a
Too short: IP                    0               0           n/a             n/a
Too short: ICMP                  0               0             0               0
Too short: IGMP                  0               0             0               0
Too short: TCP                   0               0             0               0
Too short: UDP                   0               0             0               0
Too short: IPIP                  0               0           n/a             n/a
Too short: GRE                   0               0           n/a             n/a
Too short: GRE key               0               0           n/a             n/a
Don't frag discards            n/a             n/a             0               0
Fragment packets               n/a             n/a             0               0
Fragment fragments             n/a             n/a             0               0
IPv4VlanMap dropped              0               0           n/a             n/a
IPSec NATT keep alive            0               0           n/a             n/a
MPLS Flow not found              0               0           n/a             n/a
MPLS unicast                     0               0             0               0
Size < 17                        0               0             0               0
Size   17 ..   64                8             512             0               0
Size   65 ..  127                4             304             1             102
Size  128 ..  255                0               0             0               0
Size  256 ..  511                0               0             0               0
Size  512 .. 1023                0               0             0               0
Size 1024 .. 2047                0               0             0               0
Size 2048 .. 4095                0               0             0               0
Size 4096 .. 4500                0               0             0               0
Size > 4500                      0               0             0               0

Fragmentação de IP

A fragmentação do pacote IP ocorre quando o tamanho do pacote, que inclui o cabeçalho IP, mas não nenhuns dados da camada 2 tais como a fonte/MAC de destino, o ID de VLAN, ou o FSC, quebram-se em segmentos múltiplos a fim seguir com “o ajuste MTU IP” para a relação (padrão 1500).  Neste exemplo, com o MTU ajustado ao tamanho padrão de 1500, um payload ICMP do tamanho 1472 tentado ser enviado não será fragmentado (1472 + encabeçamento do cabeçalho ICMP (8) +IP (20) = 1500), mas qualquer coisa maior do que aquele será fragmentado. Quando a fragmentação ocorre, há dois fragmentos de pacote contados nos contadores do npu e da ligação de dados da porta, um em cada cubeta apropriado-feita sob medida. Com a conclusão de um sibilo da inundação de 500 pacotes, 1000 fragmentos são enviados; 500 para o grande tamanho e 500 para o tamanho pequeno. Este exemplo foi executado em um ASR 5500 (comparado ao exemplo de emissor precedente em um ASR 5000), mas trabalha similarmente em ambas as Plataformas.

[ECS]ASR500> show ip interface 
Thursday July 16 00:31:39 UTC 2015
Intf Name: 5/29-ECS
Intf Type: Broadcast
Description:
VRF: None
IP State: UP (Bound to 5/29 vlan id 31, 802.1P prior 0, ifIndex 85786626)
IP Address: 10.213.137.105 Subnet Mask: 255.255.255.0
Bcast Address: 10.213.137.255 MTU: 1500
Resoln Type: ARP ARP timeout: 60 secs
L3 monitor LC-port switchover: Disabled
Number of Secondary Addresses: 0

port ethernet 5/29
no shutdown
vlan 31
no shutdown
bind interface 5/29-ECS ECS
#exit
#exit

Primeiramente, estabeleça uma linha de base para os contadores. Especifique o ID de VLAN para os contadores NPU (a fim confirmar que todos os sibilos têm o ID de VLAN adicionado).

[ECS]ASR5500> clear port datalink counters 5/29
Friday July 17 23:53:46 UTC 2015

[ECS]ASR5500> show port datalink counters 5/29
Friday July 17 23:53:46 UTC 2015
rCounters for port 5/29:
Line Card 10 Gigabit Ethernet Port
Rx Counter                        Data  |  Tx Counter                       Data
-----------------------  -------------- + -----------------------  -------------
RX Bytes                            406 | TX Bytes                             0
RX Unicast frames                     0 | TX Unicast frames                    0
RX Multicast frames                   4 | TX Multicast frames                  0
RX Broadcast frames                   1 | TX Broadcast frames                  0
RX Size 64 frames                     0 | TX Size 64 frames                    0
RX Size   65 ..  127 fr               5 | TX Size   65 ..  127 fr              0
RX Size  128 ..  255 fr               0 | TX Size  128 ..  255 fr              0
RX Size  256 ..  511 fr               0 | TX Size  256 ..  511 fr              0
RX Size  512 .. 1023 fr               0 | TX Size  512 .. 1023 fr              0
RX Size 1024 .. 1518 fr               0 | TX Size 1024 .. 1518 fr              0
RX Size 1519 .. 1522 fr               0 | TX Size 1519 .. 1522 fr              0
-----------------------  -------------- + -----------------------  -------------

[ECS]ASR5500> clear port npu counters 5/29 vlan 31
Friday July 17 23:53:47 UTC 2015

[ECS]ASR5500> show port npu counters 5/29 vlan 31
Friday July 17 23:53:47 UTC 2015
Counters for port 5/29 vlan id 31:

Counter                  Rx Frames       Rx Bytes      Tx Frames        Tx Bytes
-------------------- ------------- --------------- ------------- ---------------
Unicast                          0               0             0               0
Multicast                        3             196             0               0
Broadcast                        1              64             0               0
IPv4 unicast                     0               0             0               0
IPv4 non-unicast                 3             196             0               0
IPv6 unicast                     0               0             0               0
IPv6 non-unicast                 0               0             0               0
Fragments received               0               0           n/a             n/a
Packets reassembled              0               0           n/a             n/a
Fragments to kernel              0               0           n/a             n/a
HW error                         0               0           n/a             n/a
Port non-operational           539           38520             0               0
SRC MAC is multicast             0               0           n/a             n/a
Unknown VLAN tag                 0               0           n/a             n/a
Other protocols                  2             128           n/a             n/a

Sibila do tamanho 1500 bytes que o incude o cabeçalho IP é não-fragmentado mandado. O tamanho total na camada de ligação de dados (porque sae da porta) é:

1472 (payload) + 8 (cabeçalho ICMP) + 20 (cabeçalho IP) + 14 (origem de MAC/dest) + 4 (ID de VLAN) + 4 (FSC) = 1522

[ECS]ASR5500> ping  10.213.137.1 size 1472 flood
Friday July 17 23:53:48 UTC 2015
PING 10.213.137.1 (10.213.137.1) 1472(1500) bytes of data.
 
--- 10.213.137.1 ping statistics ---
500 packets transmitted, 500 received, 0% packet loss, time 422ms
rtt min/avg/max/mdev = 0.405/0.800/0.994/0.143 ms, ipg/ewma 0.845/0.802 ms

[ECS]ASR5500> show port datalink counters 5/29
Friday July 17 23:53:54 UTC 2015
Counters for port 5/29:
Line Card 10 Gigabit Ethernet Port
Rx Counter                        Data  |  Tx Counter                       Data
-----------------------  -------------- + -----------------------  -------------
RX Bytes                         771008 | TX Bytes                        765656
RX Unicast frames                   536 | TX Unicast frames                  524
RX Multicast frames                  45 | TX Multicast frames                  0
RX Broadcast frames                  20 | TX Broadcast frames                  0
RX Size 64 frames                     0 | TX Size 64 frames                    0
RX Size   65 ..  127 fr              75 | TX Size   65 ..  127 fr              0
RX Size  128 ..  255 fr              24 | TX Size  128 ..  255 fr             18
RX Size  256 ..  511 fr               2 | TX Size  256 ..  511 fr              6
RX Size  512 .. 1023 fr               0 | TX Size  512 .. 1023 fr              0
RX Size 1024 .. 1518 fr               0 | TX Size 1024 .. 1518 fr              0
RX Size 1519 .. 1522 fr             500 | TX Size 1519 .. 1522 fr            500
RX OverSize frames                    0 | TX OverSize frames                   0
RX UnderSize frames                   0 | TX UnderSize frames                  0
RX ExceedMaxSize frames               0
RX Fragment frames                    0 | TX Fragment frames                   0
RX Jabber frames                      0 | TX Jabber frames                     0
RX Control frames                     0 | TX Control frames                    0
RX Pause frames                       0 | TX Pause frames                      0
RX FCS Error frames                   0 | TX FCS Error frames                  0
RX Length Error frames                0 | TX Length Error frames               0
RX Code Error frames                  0
RX ExMaxSize Err frames               0
-----------------------  -------------- + -----------------------  -------------

[ECS]ASR5500> show port npu counters 5/29 vlan 31
Friday July 17 23:53:54 UTC 2015
Counters for port 5/29 vlan id 31:
Counter                  Rx Frames       Rx Bytes      Tx Frames        Tx Bytes
-------------------- ------------- --------------- ------------- ---------------
Unicast                        520          761900           520          762800
Multicast                       38            2811             0               0
Broadcast                       18            1408             0               0
IPv4 unicast                   538          763308           520          762800
IPv4 non-unicast                30            2027             0               0
IPv6 unicast                     0               0             0               0
IPv6 non-unicast                 8             784             0               0
Fragments received               0               0           n/a             n/a
Packets reassembled              0               0           n/a             n/a
Fragments to kernel              0               0           n/a             n/a
HW error                         0               0           n/a             n/a
Port non-operational          9482          681251             0               0
SRC MAC is multicast             0               0           n/a             n/a
Unknown VLAN tag                 0               0           n/a             n/a
Other protocols                 20            1280           n/a             n/a
Not IPv4                         8             784           n/a             n/a
...
Size    0 ..   63                0               0             0               0
Size   64 ..  127               70            5193             0               0
Size  128 ..  255               24            3408            18            2580
Size  256 ..  511                0               0             6            1980
Size  512 .. 1023                0               0             0               0
Size 1024 .. 2047              500          759000           500          759000
Size 2048 .. 4095                0               0             0               0
Size 4096 .. 8191                0               0             0               0
Size >= 8192                     0               0             0               0

Um aumento no tamanho por resultados de um byte na fragmentação (> 1500), de modo que os 500 pacotes sejam enviados como dois grupos de 500 pacotes. Note neste exemplo que o sibilo falha. Isto é provavelmente devido à rede que não pode segurar o tamanho maior do que o MTU configurado, mas aquele não é o foco deste artigo.

[ECS]ASR5500> ping 10.213.137.1 size 1473 flood
Friday July 17 23:53:55 UTC 2015
PING 10.213.137.1 (10.213.137.1) 1473(1501) bytes of data.
................................................................................
................................................................................
................................................................................
................................................................................
................................................................................
................................................................................
....................^C
--- 10.213.137.1 ping statistics ---
500 packets transmitted, 0 received, 100% packet loss, time 7124ms
, ipg/ewma 14.277/0.000 ms

[ECS]ASR5500> show port datalink counters 5/29
Friday July 17 23:54:05 UTC 2015
Counters for port 5/29:
Line Card 10 Gigabit Ethernet Port
Rx Counter Data | Tx Counter Data
----------------------- -------------- + ----------------------- -------------
RX Bytes 786615 | TX Bytes 1566628
RX Unicast frames 601 | TX Unicast frames 1567
RX Multicast frames 111 | TX Multicast frames 0
RX Broadcast frames 47 | TX Broadcast frames 0
RX Size 64 frames 0 | TX Size 64 frames 501
RX Size 65 .. 127 fr 190 | TX Size 65 .. 127 fr 2
RX Size 128 .. 255 fr 64 | TX Size 128 .. 255 fr 48
RX Size 256 .. 511 fr 5 | TX Size 256 .. 511 fr 16
RX Size 512 .. 1023 fr 0 | TX Size 512 .. 1023 fr 0
RX Size 1024 .. 1518 fr 0 | TX Size 1024 .. 1518 fr 0
RX Size 1519 .. 1522 fr 500 | TX Size 1519 .. 1522 fr 1000
RX ExceedMaxSize frames               0
RX Fragment frames                    0 | TX Fragment frames                   0
RX Jabber frames                      0 | TX Jabber frames                     0
RX Control frames                     0 | TX Control frames                    0
RX Pause frames                       0 | TX Pause frames                      0
RX FCS Error frames                   0 | TX FCS Error frames                  0
RX Length Error frames                0 | TX Length Error frames               0
RX Code Error frames                  0
RX ExMaxSize Err frames               0
----------------------- -------------- + ----------------------- -------------

[ECS]ASR5500> show port npu counters 5/29 vlan 31
Friday July 17 23:54:06 UTC 2015

Counters for port 5/29 vlan id 31:
Counter Rx Frames Rx Bytes Tx Frames Tx Bytes
-------------------- ------------- --------------- ------------- ---------------
Unicast 554 766984 1562 1549040
Multicast 94 6962 0 0
Broadcast 53 4294 0 0
IPv4 unicast 607 771278 1562 1549040
IPv4 non-unicast 73 4904 0 0
IPv6 unicast 0 0 0 0
IPv6 non-unicast 21 2058 0 0
Fragments received 0 0 n/a n/a
Packets reassembled 0 0 n/a n/a
Fragments to kernel 0 0 n/a n/a
HW error 0 0 n/a n/a
Port non-operational 25146 1805666 0 0
SRC MAC is multicast 0 0 n/a n/a
Unknown VLAN tag 0 0 n/a n/a
Other protocols 68 4742 n/a n/a
Not IPv4 21 2058 n/a n/a
...
Size 0 .. 63 0 0 501 19546
Size 64 .. 127 188 14154 2 140
Size 128 .. 255 60 8520 45 6450
Size 256 .. 511 0 0 15 4950
Size 512 .. 1023 0 0 0 0
Size 1024 .. 2047 500 759000 1000 1518000
Size 2048 .. 4095 0 0 0 0
Size 4096 .. 8191 0 0 0 0
Size >= 8192 0 0 0 0

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