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I-TAG
A multiplexing tag for
service instance scaling
in Provider Bridged Networks
Mick Seaman
[email protected]
I-TAG
• Purpose
• Architecture
• Format
• Context
802.1 July ‘04
Service instance multiplexing
Mick Seaman
2
ITAG : Purpose
• Allow upto 220 service instances in a PBN
– Particularly to address the E-LINE reqmt
– Use for E-LAN, E-TREE optional/as reqd
(more later on benefits of choice)
• Leverages existing solutions
– Complements .1Q, .1ad, .1D
– GVRP, GMRP
• No major new protocols required for scaling
802.1 July ‘04
Service instance multiplexing
Mick Seaman
3
ITAG : Architecture
I-tagging systems are “end-stations” on a provider
backbone or core network.
The backbone can be either bridged (.1D) or virtual bridged
(.1Q /.1ad)
If backbone is .1Q then tagging, detagging (ingress and
egress) rules are exactly as they are today
Tag can be added/not added and tag value dependent on
frame C-VID just as for “dual bridge model” in .1Q
<<see Paul Bottorff’s slides from Monday for diagram>>
802.1 July ‘04
Service instance multiplexing
Mick Seaman
4
I-TAG : Format (1)
• I-TAG EtherType (16 bits)
• I-TAG TCI (Tag Control Info, i.e. version, flags
8 bits)
• PRI/DE (priority, drop eligible 4 bits)
• SID (Service Instance ID – 20 bits)
• User DA (Destn. Address of conveyed ‘frame’ – 48 bits)
• User SA (Source Address of conveyed ‘frame’ – 48 bits)
16 + 128 bits total
802.1 July ‘04
Service instance multiplexing
Mick Seaman
5
802.1 July ‘04
Service instance multiplexing
SA
DA
SID
TCI
PRI/DE
EtherType
I-TAG : Format (2)
Mick Seaman
6
802.1 July ‘04
Service instance multiplexing
SID
DA
SA
S-TAG
SID
DA
SA
C-TAG
C-TAG
TCI
PRI/DE
TCI
PRI/DE
EtherType
S-TAG
S-TAG
EtherType
DA
SA
DA
SA
C-TAG
S-TAG
SID
DA
SA
PRI/DE
TCI
EtherType
DA
SA
I-TAG : Context
Mick Seaman
7
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