Subject: [Ipsec] Update on IPsec-related work within the RoHC working group

From: "Pezeshki, Jonah" <[email-masked]>
Date: Mon, 18 Jun 2007 16:09:00 -0400

IPsec working group,

The purpose of this message is to provide an update on the ongoing
IPsec-related work that is taking place within the Robust Header
Compression (RoHC) working group. 

To reduce the overhead associated with packets protected by IPsec
tunnel-mode SAs, RoHC over IPsec (RoHCoIPsec) proposes to compress the
inner headers of IP packets at the ingress of an IPsec tunnel, and
decompress these headers at the egress. 

Currently, three drafts specify RoHCoIPsec: 

"Integration of Robust Header Compression (RoHC) over IPsec Security
Associations" (draft-ietf-rohc-hcoipsec-05)
This draft outlines the framework for integrating Robust Header
Compression (RoHC) over IPsec (RoHCoIPsec). 

"IKEv2 Extensions to Support Robust Header Compression over IPsec
(RoHCoIPsec)" (draft-ietf-rohc-ikev2-extensions-hcoipsec-02)
This draft describes the IKEv2 extensions required for the operation of
RoHCoIPsec. In summary, this draft specifies the use of the Notify
Payload to negotiate RoHC channel parameters between RoHCoIPsec
instances. Specifically, the Notify payload will be used during the
IKE_AUTH and CREATE_CHILD_SA exchanges to negotiate the RoHCoIPsec
session. Note that this draft will request a new Notify Message Type
value from IANA (denoted ROHC_SUPPORTED) to indicate that the Notify
payload is conveying RoHC channel parameters.

"IPsec Extensions to Support Robust Header Compression over IPsec
(RoHCoIPsec)" (draft-ertekin-rohc-ipsec-extensions-hcoipsec-01)
This draft describes the IPsec extensions required for the operation of
RoHCoIPsec. In summary, this draft specifies several items:
(1) the addition of several processing info fields to the SPD, which
will allow it to include per-channel RoHC parameters. These parameters
will dictate packet disposition for traffic that is to be compressed via
RoHC, and subsequently protected by IPsec. 
(2) the addition of a "RoHC Data Item" field in the SAD that stores the
negotiated RoHC parameters for each established SA. 
(3) the use of the "Next Header" field of the AH/ESP header to identify
a RoHC packet headers.

We are soliciting for comments from the IPsec experts on this mailer
regarding all three drafts. 

Thank you,
 
Jonah Pezeshki
Consultant
Booz | Allen | Hamilton
(703) 984-0810

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From: Markku Savela <[email-masked]>
Date: Mon, 18 Jun 2007 23:26:29 +0300

> Compression (RoHC) over IPsec (RoHCoIPsec). 

Couldn't this same be achieved by use of IPsec compression transform
by defining a "RoHC" compression algorithm?

---

From: "Pezeshki, Jonah" <[email-masked]>
Date: Tue, 19 Jun 2007 10:50:37 -0400

Markku,
 
Thank you for your comment regarding our drafts.  One point that I
failed to clarify in the summary of the drafts (from the previous
e-mail) is that RoHC is not an alternative to IP compression (IPcomp).
IPcomp focuses on algorithmically compressing the contents (i.e.,
payload) of the packet, while RoHC exploits intra- and inter-packet
redundancies of network and transport-layer header fields to effectively
compress packet headers.  Due to this operational difference, RoHC
cannot be defined in the same way as IPcomp is, due to RoHC's need to
dynamically negotiate RoHC channel parameters before operation (thus the
need to extend IKEv2 to negotiate these parameters, and IPsec to store
these values).  Furthermore, it should have been mentioned that the
framework draft (draft-ietf-rohc-hcoipsec-05) and the IPsec extensions
draft (draft-ertekin-rohc-ipsec-extensions-hcoipsec-01) both describe
how RoHCoIPsec and IPcomp can be implemented together in a nested
fashion.

Once again thank you for your comments; hopefully my email addresses
your question.

Jonah

-----Original Message-----
From: Markku Savela [mailto:[email-masked]] 
Sent: Monday, June 18, 2007 4:26 PM
To: Pezeshki, Jonah
Cc: [email-masked]; Ertekin, Emre
Subject: Re: [Ipsec] Update on IPsec-related work within the RoHC
working group

> Associations" (draft-ietf-rohc-hcoipsec-05) This draft outlines the 
> framework for integrating Robust Header Compression (RoHC) over IPsec 
> (RoHCoIPsec).

Couldn't this same be achieved by use of IPsec compression transform by
defining a "RoHC" compression algorithm?