Re: hub-spoke topology and response time

Hey Scott, Mihai.

Setup I am playing with has all routers' CPUs idling so I doubt it is a
CPU-related. And it is not a hub-and-spoke specific, just a simple FR
link shows different directed broadcast behavior comparing to unicast;
namely, for the broadcast one it grows from 4 ms up to around 100 ms and
then drops back to 4 ms. And this is quasi-periodic, happens every 2
minutes and 30 seconds +-4 seconds. :-) I played around with
"frame-relay broadcast-queue" settings for that interface and ICMP
packet size, didn't seem to make any difference.
http://www.cisco.com/en/US/tech/tk713/tk237/technologies_tech_note09186a008014f8a7.shtml#topic9

I guess it might be also platform and/or interface specific for period
and min/max reply time, my setup is 2611 routers.

R1#ping ip 2.2.2.255 re 300

Type escape sequence to abort.
Sending 300, 100-byte ICMP Echos to 2.2.2.255, timeout is 2 seconds:

Reply to request 0 from 2.2.2.2, 48 ms
Reply to request 1 from 2.2.2.2, 52 ms
Reply to request 2 from 2.2.2.2, 52 ms
Reply to request 3 from 2.2.2.2, 52 ms
Reply to request 4 from 2.2.2.2, 56 ms
Reply to request 5 from 2.2.2.2, 56 ms
Reply to request 6 from 2.2.2.2, 56 ms
Reply to request 7 from 2.2.2.2, 57 ms
Reply to request 8 from 2.2.2.2, 60 ms
Reply to request 9 from 2.2.2.2, 60 ms
Reply to request 10 from 2.2.2.2, 60 ms
Reply to request 11 from 2.2.2.2, 64 ms
Reply to request 12 from 2.2.2.2, 76 ms
Reply to request 13 from 2.2.2.2, 76 ms
Reply to request 14 from 2.2.2.2, 77 ms
Reply to request 15 from 2.2.2.2, 80 ms
Reply to request 16 from 2.2.2.2, 80 ms
Reply to request 17 from 2.2.2.2, 80 ms
Reply to request 18 from 2.2.2.2, 84 ms
Reply to request 19 from 2.2.2.2, 84 ms
Reply to request 20 from 2.2.2.2, 84 ms
Reply to request 21 from 2.2.2.2, 85 ms
Reply to request 22 from 2.2.2.2, 88 ms
Reply to request 23 from 2.2.2.2, 88 ms
Reply to request 24 from 2.2.2.2, 88 ms
Reply to request 25 from 2.2.2.2, 92 ms
Reply to request 26 from 2.2.2.2, 92 ms
Reply to request 27 from 2.2.2.2, 92 ms
Reply to request 28 from 2.2.2.2, 93 ms
Reply to request 29 from 2.2.2.2, 96 ms
Reply to request 30 from 2.2.2.2, 96 ms
Reply to request 31 from 2.2.2.2, 96 ms
Reply to request 32 from 2.2.2.2, 100 ms
Reply to request 33 from 2.2.2.2, 100 ms
Reply to request 34 from 2.2.2.2, 100 ms
Reply to request 35 from 2.2.2.2, 101 ms
Reply to request 36 from 2.2.2.2, 104 ms
Reply to request 37 from 2.2.2.2, 104 ms
Reply to request 38 from 2.2.2.2, 4 ms
Reply to request 39 from 2.2.2.2, 8 ms
Reply to request 40 from 2.2.2.2, 8 ms
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Reply to request 44 from 2.2.2.2, 8 ms
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Reply to request 46 from 2.2.2.2, 12 ms
Reply to request 47 from 2.2.2.2, 12 ms
Reply to request 48 from 2.2.2.2, 12 ms
Reply to request 49 from 2.2.2.2, 12 ms
Reply to request 50 from 2.2.2.2, 16 ms
Reply to request 51 from 2.2.2.2, 16 ms
Reply to request 52 from 2.2.2.2, 16 ms
Reply to request 53 from 2.2.2.2, 17 ms
Reply to request 54 from 2.2.2.2, 20 ms
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Reply to request 56 from 2.2.2.2, 20 ms
Reply to request 57 from 2.2.2.2, 24 ms
Reply to request 58 from 2.2.2.2, 24 ms
Reply to request 59 from 2.2.2.2, 24 ms
Reply to request 60 from 2.2.2.2, 25 ms
Reply to request 61 from 2.2.2.2, 28 ms
Reply to request 62 from 2.2.2.2, 28 ms
Reply to request 63 from 2.2.2.2, 28 ms
Reply to request 64 from 2.2.2.2, 32 ms
Reply to request 65 from 2.2.2.2, 32 ms
Reply to request 66 from 2.2.2.2, 32 ms
Reply to request 67 from 2.2.2.2, 32 ms
Reply to request 68 from 2.2.2.2, 36 ms
Reply to request 69 from 2.2.2.2, 36 ms

Reply to request 70 from 2.2.2.2, 36 ms
Reply to request 71 from 2.2.2.2, 40 ms
Reply to request 72 from 2.2.2.2, 40 ms
Reply to request 73 from 2.2.2.2, 40 ms
Reply to request 74 from 2.2.2.2, 40 ms
Reply to request 75 from 2.2.2.2, 44 ms
Reply to request 76 from 2.2.2.2, 44 ms
Reply to request 77 from 2.2.2.2, 44 ms
Reply to request 78 from 2.2.2.2, 48 ms
Reply to request 79 from 2.2.2.2, 48 ms
Reply to request 80 from 2.2.2.2, 48 ms
Reply to request 81 from 2.2.2.2, 48 ms
Reply to request 82 from 2.2.2.2, 52 ms
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Reply to request 84 from 2.2.2.2, 52 ms
Reply to request 85 from 2.2.2.2, 56 ms
Reply to request 86 from 2.2.2.2, 56 ms
Reply to request 87 from 2.2.2.2, 56 ms
Reply to request 88 from 2.2.2.2, 56 ms
Reply to request 89 from 2.2.2.2, 60 ms
Reply to request 90 from 2.2.2.2, 60 ms
Reply to request 91 from 2.2.2.2, 60 ms
Reply to request 92 from 2.2.2.2, 61 ms
Reply to request 93 from 2.2.2.2, 64 ms
Reply to request 94 from 2.2.2.2, 64 ms
Reply to request 95 from 2.2.2.2, 64 ms
Reply to request 96 from 2.2.2.2, 68 ms
Reply to request 97 from 2.2.2.2, 68 ms
Reply to request 98 from 2.2.2.2, 68 ms
Reply to request 99 from 2.2.2.2, 69 ms
Reply to request 100 from 2.2.2.2, 72 ms
Reply to request 101 from 2.2.2.2, 84 ms
Reply to request 102 from 2.2.2.2, 84 ms
Reply to request 103 from 2.2.2.2, 88 ms
Reply to request 104 from 2.2.2.2, 88 ms
Reply to request 105 from 2.2.2.2, 88 ms
Reply to request 106 from 2.2.2.2, 89 ms
Reply to request 107 from 2.2.2.2, 92 ms
Reply to request 108 from 2.2.2.2, 92 ms
Reply to request 109 from 2.2.2.2, 92 ms
Reply to request 110 from 2.2.2.2, 96 ms
Reply to request 111 from 2.2.2.2, 96 ms
Reply to request 112 from 2.2.2.2, 96 ms
Reply to request 113 from 2.2.2.2, 97 ms
Reply to request 114 from 2.2.2.2, 100 ms
Reply to request 115 from 2.2.2.2, 100 ms
Reply to request 116 from 2.2.2.2, 100 ms
Reply to request 117 from 2.2.2.2, 4 ms
Reply to request 118 from 2.2.2.2, 4 ms
Reply to request 119 from 2.2.2.2, 4 ms
Reply to request 120 from 2.2.2.2, 105 ms
Reply to request 121 from 2.2.2.2, 8 ms
Reply to request 122 from 2.2.2.2, 8 ms
Reply to request 123 from 2.2.2.2, 8 ms
Reply to request 124 from 2.2.2.2, 12 ms
Reply to request 125 from 2.2.2.2, 12 ms
Reply to request 126 from 2.2.2.2, 12 ms
Reply to request 127 from 2.2.2.2, 12 ms
Reply to request 128 from 2.2.2.2, 16 ms
Reply to request 129 from 2.2.2.2, 16 ms
Reply to request 130 from 2.2.2.2, 24 ms
Reply to request 131 from 2.2.2.2, 24 ms
Reply to request 132 from 2.2.2.2, 24 ms
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Reply to request 134 from 2.2.2.2, 24 ms
Reply to request 135 from 2.2.2.2, 28 ms
Reply to request 136 from 2.2.2.2, 28 ms
Reply to request 137 from 2.2.2.2, 28 ms
Reply to request 138 from 2.2.2.2, 29 ms
Reply to request 139 from 2.2.2.2, 32 ms

Reply to request 140 from 2.2.2.2, 32 ms
Reply to request 141 from 2.2.2.2, 32 ms
Reply to request 142 from 2.2.2.2, 36 ms
Reply to request 143 from 2.2.2.2, 36 ms
Reply to request 144 from 2.2.2.2, 36 ms
Reply to request 145 from 2.2.2.2, 37 ms
Reply to request 146 from 2.2.2.2, 40 ms
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Reply to request 148 from 2.2.2.2, 40 ms
Reply to request 149 from 2.2.2.2, 44 ms
Reply to request 150 from 2.2.2.2, 44 ms
Reply to request 151 from 2.2.2.2, 44 ms
Reply to request 152 from 2.2.2.2, 45 ms
Reply to request 153 from 2.2.2.2, 48 ms
Reply to request 154 from 2.2.2.2, 48 ms
Reply to request 155 from 2.2.2.2, 48 ms
Reply to request 156 from 2.2.2.2, 52 ms
Reply to request 157 from 2.2.2.2, 52 ms
Reply to request 158 from 2.2.2.2, 52 ms
Reply to request 159 from 2.2.2.2, 52 ms
Reply to request 160 from 2.2.2.2, 56 ms
Reply to request 161 from 2.2.2.2, 56 ms
Reply to request 162 from 2.2.2.2, 56 ms
Reply to request 163 from 2.2.2.2, 60 ms
Reply to request 164 from 2.2.2.2, 60 ms
Reply to request 165 from 2.2.2.2, 60 ms
Reply to request 166 from 2.2.2.2, 60 ms
Reply to request 167 from 2.2.2.2, 64 ms
Reply to request 168 from 2.2.2.2, 64 ms
Reply to request 169 from 2.2.2.2, 64 ms
Reply to request 170 from 2.2.2.2, 68 ms
Reply to request 171 from 2.2.2.2, 68 ms
Reply to request 172 from 2.2.2.2, 68 ms
Reply to request 173 from 2.2.2.2, 68 ms
Reply to request 174 from 2.2.2.2, 72 ms
Reply to request 175 from 2.2.2.2, 72 ms
Reply to request 176 from 2.2.2.2, 72 ms
Reply to request 177 from 2.2.2.2, 73 ms
Reply to request 178 from 2.2.2.2, 76 ms
Reply to request 179 from 2.2.2.2, 76 ms
Reply to request 180 from 2.2.2.2, 76 ms
Reply to request 181 from 2.2.2.2, 80 ms
Reply to request 182 from 2.2.2.2, 80 ms
Reply to request 183 from 2.2.2.2, 96 ms
Reply to request 184 from 2.2.2.2, 97 ms
Reply to request 185 from 2.2.2.2, 100 ms
Reply to request 186 from 2.2.2.2, 100 ms
Reply to request 187 from 2.2.2.2, 100 ms
Reply to request 188 from 2.2.2.2, 104 ms
Reply to request 189 from 2.2.2.2, 4 ms
Reply to request 190 from 2.2.2.2, 120 ms
Reply to request 191 from 2.2.2.2, 105 ms
Reply to request 192 from 2.2.2.2, 8 ms
Reply to request 193 from 2.2.2.2, 8 ms
Reply to request 194 from 2.2.2.2, 8 ms
Reply to request 195 from 2.2.2.2, 12 ms
Reply to request 196 from 2.2.2.2, 12 ms
Reply to request 197 from 2.2.2.2, 12 ms
Reply to request 198 from 2.2.2.2, 12 ms
Reply to request 199 from 2.2.2.2, 16 ms
Reply to request 200 from 2.2.2.2, 16 ms
Reply to request 201 from 2.2.2.2, 16 ms
Reply to request 202 from 2.2.2.2, 20 ms
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Reply to request 206 from 2.2.2.2, 24 ms
Reply to request 207 from 2.2.2.2, 24 ms
Reply to request 208 from 2.2.2.2, 24 ms
Reply to request 209 from 2.2.2.2, 28 ms

Reply to request 210 from 2.2.2.2, 28 ms
Reply to request 211 from 2.2.2.2, 28 ms
Reply to request 212 from 2.2.2.2, 28 ms
Reply to request 213 from 2.2.2.2, 32 ms
Reply to request 214 from 2.2.2.2, 32 ms
Reply to request 215 from 2.2.2.2, 32 ms
Reply to request 216 from 2.2.2.2, 33 ms
Reply to request 217 from 2.2.2.2, 36 ms
Reply to request 218 from 2.2.2.2, 36 ms
Reply to request 219 from 2.2.2.2, 36 ms
Reply to request 220 from 2.2.2.2, 40 ms
Reply to request 221 from 2.2.2.2, 40 ms
Reply to request 222 from 2.2.2.2, 40 ms
Reply to request 223 from 2.2.2.2, 41 ms
Reply to request 224 from 2.2.2.2, 44 ms
Reply to request 225 from 2.2.2.2, 44 ms
Reply to request 226 from 2.2.2.2, 44 ms
Reply to request 227 from 2.2.2.2, 48 ms
Reply to request 228 from 2.2.2.2, 48 ms
Reply to request 229 from 2.2.2.2, 48 ms
Reply to request 230 from 2.2.2.2, 49 ms
Reply to request 231 from 2.2.2.2, 52 ms
Reply to request 232 from 2.2.2.2, 52 ms
Reply to request 233 from 2.2.2.2, 52 ms
Reply to request 234 from 2.2.2.2, 56 ms
Reply to request 235 from 2.2.2.2, 56 ms
Reply to request 236 from 2.2.2.2, 56 ms
Reply to request 237 from 2.2.2.2, 57 ms
Reply to request 238 from 2.2.2.2, 60 ms
Reply to request 239 from 2.2.2.2, 60 ms
Reply to request 240 from 2.2.2.2, 60 ms
Reply to request 241 from 2.2.2.2, 64 ms
Reply to request 242 from 2.2.2.2, 64 ms
Reply to request 243 from 2.2.2.2, 64 ms
Reply to request 244 from 2.2.2.2, 65 ms
Reply to request 245 from 2.2.2.2, 68 ms
Reply to request 246 from 2.2.2.2, 68 ms
Reply to request 247 from 2.2.2.2, 68 ms
Reply to request 248 from 2.2.2.2, 72 ms
Reply to request 249 from 2.2.2.2, 72 ms
Reply to request 250 from 2.2.2.2, 72 ms
Reply to request 251 from 2.2.2.2, 72 ms
Reply to request 252 from 2.2.2.2, 76 ms
Reply to request 253 from 2.2.2.2, 76 ms
Reply to request 254 from 2.2.2.2, 76 ms
Reply to request 255 from 2.2.2.2, 76 ms
Reply to request 256 from 2.2.2.2, 76 ms
Reply to request 257 from 2.2.2.2, 76 ms
Reply to request 258 from 2.2.2.2, 76 ms
Reply to request 259 from 2.2.2.2, 80 ms
Reply to request 260 from 2.2.2.2, 80 ms
Reply to request 261 from 2.2.2.2, 80 ms
Reply to request 262 from 2.2.2.2, 81 ms
Reply to request 263 from 2.2.2.2, 84 ms
Reply to request 264 from 2.2.2.2, 84 ms
Reply to request 265 from 2.2.2.2, 84 ms
Reply to request 266 from 2.2.2.2, 88 ms
Reply to request 267 from 2.2.2.2, 88 ms
Reply to request 268 from 2.2.2.2, 88 ms
Reply to request 269 from 2.2.2.2, 89 ms
Reply to request 270 from 2.2.2.2, 92 ms
Reply to request 271 from 2.2.2.2, 92 ms
Reply to request 272 from 2.2.2.2, 92 ms
Reply to request 273 from 2.2.2.2, 96 ms
Reply to request 274 from 2.2.2.2, 96 ms
Reply to request 275 from 2.2.2.2, 96 ms
Reply to request 276 from 2.2.2.2, 97 ms
Reply to request 277 from 2.2.2.2, 100 ms
Reply to request 278 from 2.2.2.2, 100 ms
Reply to request 279 from 2.2.2.2, 100 ms

Reply to request 280 from 2.2.2.2, 4 ms
Reply to request 281 from 2.2.2.2, 104 ms
Reply to request 282 from 2.2.2.2, 4 ms
Reply to request 283 from 2.2.2.2, 105 ms
Reply to request 284 from 2.2.2.2, 8 ms
Reply to request 285 from 2.2.2.2, 8 ms
Reply to request 286 from 2.2.2.2, 8 ms
Reply to request 287 from 2.2.2.2, 12 ms
Reply to request 288 from 2.2.2.2, 12 ms
Reply to request 289 from 2.2.2.2, 12 ms
Reply to request 290 from 2.2.2.2, 12 ms
Reply to request 291 from 2.2.2.2, 16 ms
Reply to request 292 from 2.2.2.2, 16 ms
Reply to request 293 from 2.2.2.2, 16 ms
Reply to request 294 from 2.2.2.2, 20 ms
Reply to request 295 from 2.2.2.2, 20 ms
Reply to request 296 from 2.2.2.2, 20 ms
Reply to request 297 from 2.2.2.2, 20 ms
Reply to request 298 from 2.2.2.2, 24 ms
Reply to request 299 from 2.2.2.2, 24 ms

Scott M Vermillion wrote:
> Hi Mihai,
>
> Just a total guess here but I'm thinking internal interrupt scheduling
> w/in IOS. Likely the broadcast traffic is left in the CPU waiting
> room a little longer on the receiving end relative to the unicast
> traffic.
>
> Sorry for the late reply but I have a few thousand backlogged messages
> yet to go and it doesn't appear as if you ever got any other response...
>
> Regards,
>
> Scott
>
>
> On Jul 2, 2009, at 6:11 , mihai.grigore_at_orange-ftgroup.com wrote:
>
>> Fellow experts,
>>
>> I have a simple topology: R5 is hub and R1, R3 are spokes.
>> IP range is 155.1.0.x/24 where x=router number.
>> I am using static FR mapping
>>
>> R5#sh fram map
>> Serial0/0 (up): ip 155.1.0.1 dlci 501(0x1F5,0x7C50), static,
>> broadcast,
>> CISCO, status defined, active
>> Serial0/0 (up): ip 155.1.0.3 dlci 503(0x1F7,0x7C70), static,
>> broadcast,
>> CISCO, status defined, active
>>
>> I have a question: why unicast and broadcast response times are so
>> different?
>>
>> For unicast, I have about 57 ms:
>>
>> R5#pi 155.1.0.1
>>
>> Type escape sequence to abort.
>> Sending 5, 100-byte ICMP Echos to 155.1.0.1, timeout is 2 seconds:
>> !!!!!
>> Success rate is 100 percent (5/5), round-trip min/avg/max = 56/57/60 ms
>> R5#pi 155.1.0.3
>>
>> Type escape sequence to abort.
>> Sending 5, 100-byte ICMP Echos to 155.1.0.3, timeout is 2 seconds:
>> !!!!!
>> Success rate is 100 percent (5/5), round-trip min/avg/max = 56/57/60 ms
>>
>>
>> For broadcast, I have almost double:
>>
>> R5#pi 255.255.255.255
>>
>> Type escape sequence to abort.
>> Sending 5, 100-byte ICMP Echos to 255.255.255.255, timeout is 2 seconds:
>>
>> Reply to request 0 from 155.1.0.3, 88 ms
>> Reply to request 0 from 155.1.0.1, 100 ms
>> Reply to request 1 from 155.1.0.3, 88 ms
>> Reply to request 1 from 155.1.0.1, 100 ms
>> Reply to request 2 from 155.1.0.3, 113 ms
>> Reply to request 2 from 155.1.0.1, 125 ms
>> Reply to request 3 from 155.1.0.3, 116 ms
>> Reply to request 3 from 155.1.0.1, 128 ms
>> Reply to request 4 from 155.1.0.3, 116 ms
>> Reply to request 4 from 155.1.0.1, 128 ms
>>
>>
>> Not a big deal, but anyone tell me why this?
>>
>> TIA, MIhai
>>
>>
>> Blogs and organic groups at http://www.ccie.net
>>
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>
>
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>
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Received on Wed Jul 22 2009 - 21:38:54 ART