IETF seamoby WG 2003-07-17 cabo@tzi.org 1

ROHC CT issues

Carsten Bormann, 2003-07-17

IETF seamoby WG 2003-07-17 cabo@tzi.org 2

The RFC 3095 architecture

• Header compression is on a channel• Multiple compression contexts are

multiplexed via a CID (compression context ID)

• HC state is L2 state– In a bridged system, lives on AP, not AR

• There are multiple profiles (RTP, TCP, …)– Some even have special state at L2 (LLA)

IETF seamoby WG 2003-07-17 cabo@tzi.org 3

Implications (1)

• Handover creates a new channel– Normally, negotiation required!

• Some context fields may need to change (e.g., IP address)– These are profile specific

• Context was active before transfer– Race conditions possible!

IETF seamoby WG 2003-07-17 cabo@tzi.org 4

Implications (2)

• How does MN know that CT was done?– And what CT parameters were used, if any?– What is the CID mapping on nAR?– Any other interesting channel parameters?

CT operation must be part of HC profile– Quite similar to ROHC context replication:

draft-ietf-rohc-context-replication-00.txt