Swinog-3, 19 September 2001

IP-Multicast operational experience

André Chapuis, IP-Plus

Swinog-3, Multicast operational experience

Network design

Standard internet protocols

– PIM-SM– MSDP– MBGP

Redundant RP with anycast-RP

Recommended filters for MSDP/PIM

– ftp://ftpeng.cisco.com/ipmulticast/config-notes/msdp-sa-filter.txt Customer’s RP filtered

– Accept only SA-messages originated by specific RP’s Congruent IMBGP/IBGP topologies

MBGP only where necessary

Swinog-3, Multicast operational experience

Network layout: MBGP

Swinog-3, Multicast operational experience

Network layout: MSDP

Swinog-3, Multicast operational experience

Observations/problems

MBGP: RPF checks:

IOS 12.0(7)T: MBGP used to leak into the unicast RIB ! First trial abruptly stopped…

Distance-preferred lookups, not longest-match ! Problems with aggregates (network statements)

Where to inject prefixes into MBGP if RPF checks are done with network statements rather than IGP route !

Confed-external IMBGP were set a distance of 20 (bug) Occurred in IOS 12.0(10)S1 only Caused routing loops

MBGP/BGP distance needs manual adaptation

Swinog-3, Multicast operational experience

Observations/problems

MSDP: peer-RPF checks:

How it works: When SA-message received, MSDP originator-id

is RPF checked with MBGP source AS (to avoid loops when re-transmitting SA-messages)

Issue: if ISP1 uses parallel MSDP/MBGP peerings and

ISP2 only MSDP from its RP: RPF fails

Seen with ‘debug ip msdp’ (use with care !)

Use I-MSDP sessions or mesh-groups to bypass RPF checks

Swinog-3, Multicast operational experience

Observations/problems

MDS (Multicast Distributed Switching) bug(?) on IOS 12.0(16.6)S2, Cisco7513, VIP4-80, PA-H, Frame-relay p2p sub-interfaces:

MDS stops forwarding packets after some time (~1min) Turn off MDS

Could only be seen with sh ip mroute 233.21.90.1 count because all the routing tables and forwarding tables were looking fine !

Always check packet-forwarding (once the multicast RT is OK)

Swinog-3, Multicast operational experience

Observations/problems

i64beb-eng#sh ip mrou 159.134.237.179 233.21.90.1 count

IP Multicast Statistics

207 routes using 72786 bytes of memory

28 groups, 6.39 average sources per group

Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kilobits per second

Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)

Group: 233.21.90.1, Source count: 51, Group pkt count: 234997

Source: 159.134.237.179/32, Forwarding: 226320/44/663/247, Other: 226320/0/0

Swinog-3, Multicast operational experience

Debugging

mtrace <group> : uses RPF neighbors up to the source

mtrace <source> <dest> <group>: follows SPT for the group

mstat <source> <dest> <group>: gives packet-loss along the SPT

show ip mroute <group> count: gives actually forwarded packets

http://www.on-the-i.com/mt/index.html: tests from your host !

Swinog-3, Multicast operational experience

Mtrace example i64beb-eng#mtrace 159.134.237.179 195.65.89.1 233.20.90.1

Type escape sequence to abort.

Mtrace from 159.134.237.179 to 195.65.89.1 via group 233.20.90.1

From source (dipsy.av.eircom.net) to destination (i64beb-eng-FastEthernet0-0.ip-plus.net)

Querying full reverse path...

0 i64beb-eng-FastEthernet0-0.ip-plus.net (195.65.89.1)

-1 i64beb-eng-FastEthernet0-0.ip-plus.net (195.65.89.1) PIM [default]

-2 i64beb-021-atm4-0.ip-plus.net (164.128.156.249) PIM/MBGP [159.134.0.0/16]

-3 i62beb-031-fas-2-0.ip-plus.net (164.128.129.230) PIM [159.134.0.0/16]

-4 i64bei-000-Hssi1-0-5.ip-plus.net (164.128.49.13) PIM/MBGP [159.134.0.0/16]

-5 ges-005-Serial3-1.ip-plus.net (164.128.33.129) PIM/MBGP [159.134.0.0/16]

-6 lon-000-Serial2-0.ip-plus.net (164.128.34.14) PIM/MBGP [159.134.0.0/16]

-7 lon-005-POS2-0.ip-plus.net (164.128.33.14) PIM/MBGP [159.134.0.0/16]

-8 fa0.mcast1.thn.london.eircom.net (195.66.230.20) PIM [159.134.237.176/29]

-9 fa5-0-0.core1.thn.london.eircom.net (159.134.191.49) PIM [159.134.237.176/29]

-10 pos1-0-0.core1.cra.dublin.eircom.net (159.134.191.97) PIM [159.134.237.176/29]

-11 e0.mbone.cra.dublin.eircom.net (159.134.192.55) PIM [159.134.237.176/29]

-12 dipsy.av.eircom.net (159.134.237.179)

i64beb-eng#

Swinog-3, Multicast operational experience

Facts

Global MBGP table contains 3751 entries

IP-Plus currently has 15 multicast peerings

Some popular Websites offer multicast contents:

– www.on-the-i.com– www.broadcast.com (Yahoo, through AS3356

(Level3)– From last week on, Mbone session:

– UO internal channel 2 sends CNN live