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NOTES
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NOTES
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- weird RR behaviors
- "A" behavior -- Cisco
- MPLS enabled routers don't add RR for outgoing MPLS connections
- "B" behavior -- "Juniper" ?
- add outgoing interface even if packet is bounced
- "stupid" behavior : don't bounce RR packets, bounce non-rr packets
mark RR packets on outgoing packets
examples: 216.24.186.{4,6,33} from uw to cornell
OrgName: National LambdaRail, IndianaU ?? http://www.nlr.net/
explanation: firewall blocking icmp bounce > 48 bytes?
- use id increment rate to verify
- "flakey" behavior: sometime mark RR packets, sometimes not
Cisco under load?
- "DropsRR"
- won't let packets with RR pass by
- apply the "off by one" network alias connection rule
- some planetlab systems calls take >1 sec to complete
- some weird middle boxes uncheck DF bit, screws up optimization
#################################################################
Problematic Trace
ttl nRR entries RRtype Inference source
-----------------------------------------------
1 0 A 2 is not type B (#2:beta)
2 1 A 3 has +2 entries (#1:alpha)
3 3 B +2 --> always B (#0:alpha)
4 3 A 5 is +2: (#4:beta)
5 5 B +2 --> always B (#3:alpha)
6 5 N +0,+0 --> (#5:gamma)
7 5 A/N
8 6 N/B
9 6 A in/new hop off by 1: (#7:epsilon)
10 7 A in/new hop off by 1: (#6:epsilon)
11 8 A 10 is A (#8,beta)
Rules:
Rule alpha: +2 from prev --> you are B and prev is A
Rule beta : +1 from prev --> you are B and prev is N or B
-OR- you are A or N and prev is A
Rule gamma: +0 from prev --> you are A or N and prev is N or B
Rule delta: if you are +0 and next is +0, you are N
Rule epsilon: if +1 and inhop ip and new RR hop ip are off by 1, then you are A and prev is A
Rule zeta: if out of band ping shows RR, then not N
Rule eta: are inhop and new RR hop alises? yes, then B, no then A or N
GUESS:
g = nRR entries + #N's upstream:
- if g == ttl, then B
- if g == ttl-1
Further note:
a sequence of 0,1,2,3,4,5,6,7,8,9 nRR's is indeterminant:
if could be all A's or N,B,B,B...
-----------------------------------------------------------------------------------------------
Calc queue size as a function of min delay:
say average packet is 80 bytes, then if we are going at b Bytes/s,
then max queue size should be b/80 or 500kbps --> 64000/80 == 800 packets
--------------------------------------------------------------------------------------------
MPLS stuff:
Cisco explanation: `no mpls ip propagate-ttl`
http://www.cisco.com/en/US/tech/tk436/tk428/technologies_tech_note09186a008020a42a.shtml
Good MPLS tutorial:
http://www.iec.org/online/tutorials/mpls/topic03.html
Can also get MPLS info from ping:
"MPLS OAM Tools for Troubleshooting MPLS Networks" http://www.cisco.com/application/pdf/en/us/guest/netsol/ns172/c654/cdccont_0900aecd80272b7f.pdf