2.8.19 Access Link Intermediaries Assisting Services (alias) Bof

Current Meeting Report

meetingAccess Link Intermediaries Assisting Services BOF (alias)

Tuesday, November 11 at 1415-1515

CHAIRS: Kevin Fall (kfall@eecs.berkeley.edu) 
        Hui-Lan Lu (huilanlu@bell-labs.com)

(Notes taken by Igor Faynberg, faynberg@bell-labs.com)

The meeting started with the Chairs' welcome and the presentation of the 

1.      Agenda bashing 
2.      Status update (Hui-Lan Lu and Kevin Fall)
3.      Trouble with triggers, Bernard Aboba (15 min.)
4.      Example intermediary services, Thomas Woo (10 min.)
5.      Some observations, Kevin Fall (10 min.)
6.      Open discussion (group name change?)
7.      Wrapping up

The agenda was accepted; I volunteered to take the notes (there were no 
other volunteers). The meeting then proceeded strictly according to the 

Item 2: Hui-Lan presented the status. Proposed charter has been under the 
IESG review, and it was revised based on IESG and mailing list 
feedback. TheRevised charter was posted to the mailing list yesterday 
(further discussion, if any, to take place on line). Kevin reviewed the 

1: Added Kevin's definition of transport intermediaries
2: Enumerated interaction details between intermediaries and 
endpoints: discovery, request, control, and information reporting
3: Clarified that the security association was optional
4: Expanded the survey to allow for planned/desired transport 
5: In-scope transport intermediary services are to be defined after the 
working group is formed
6: Updated the deliverables and milestones.

There was no discussion. The meeting was reminded of the important 
summary of the present BoF information: 






Item 3: Bernard Aboba, Microsoft. "Trouble with triggers."  Trigger is a 
lower layer indication, also known as a "hint" in DNA. The problem is that 
the hint can be wrong, but any trigger requires an action. Still, 
implementations must be robust in the face of misleading "hints". 
Examples of bad hints: Using SSID as a "hint" in moving from one private 
network to another; SSID names the ESS, not the network prefix. As the 
result, host moves from one "default" SSID to another, and concludes that it 
is on the same link. Another example is "Link down" (Media Sense 
implemented in Windows 2000). Some applications (foolishly) consumed the 
"hint," and so TCP connections were closed after momentary 
connectivity loss. The "Link up" example: IEEE 802.11-1999: 
Re-association Response and IEEE 802.11i: Completion of 4-way 
handshake. Those result in DHCP packets going out prior to completion of L2 
authorization and being dropped. Then TCP connections go into slow start. 
Alias  should know which hints are "strong" and which are "weak", verify 
them and recover from misleading hints. Suggestions on how to proceed with 
references to the specific drafts. Motto: "Trust but verify."


Comment: IEEE should deal with 802 link. This was followed by two 
positive comments in support of the presentation. 

Q: It is good you noted Wi-Fi link matters. Let us look at the air links 
more. We have the same problem in CDMA2000, right? Specifically, base 
stations, which have to deal with the faulty air links. This is, by the 
way, why I am here. Do you think we should look at the PDSN?
A: Yes, this needs to be looked at in detail. We should look at costs on 
both sides.
Comment ( Steve Bellovin): The best way is to get the "hint" right, and it 
will improve the performance.

Q: Lots of finger pointing at layer two. But what about layer 3? In these 
situation, if the network got away, how long do you wait until the user 
notices that "it is broken." 
A: I agree about the layer 3.

Comment about firewalls being problematic. How do hints go through 

Item 4. Presentation of  Kevin Fall, Intel Research: Some 
Observations for ALIAS*
 Presentation goes over the troubles with 'Access' links and relevant 
issues: "State vs No State," "Who Signals?", and ICMP.  A picture is 
presented that gives examples of the access links (including wireless 
ones). The direct vs. indirect signaling from middle box 
[intermediary] to the end point. Brainstorming suggestions for ICMP 
messages: "middlebox on path," "radical link change," "wrong source 
address." But maybe "access" link is two problematic to define; we can drop 
"A" in the name and call the group "Link Intermediaries for Enhanced 
Services (LIES)". And then there is an issue of maintanance of states, 
secure sessions with midboxes. Perhaps simple (stateless) async 
notification would work. Threat model.  Not much against on-path 

Comment: Host has ways to determine reachability in the case of route 
Comment: We need to know who initiates the protocol. Depending on the 
choice, the threat models will be different. (We need to avoid "lies.")

Q: What are these intermediaries and why do I need them. What's in it for 
A (from the floor): Intermediaries are there to perform services. Base 
station or a PDSN node, mentioned before, is an example of an 
intermediary that does more than plain routing with the traffic that 
originates or terminates on wireless links. They are also there to 
provide extra services (such as TCP performance improvement or some other 
QoS mechanism). What's in it for me? I can use these extra services, if I 
want to, or I can reject them.

Comment: Layer 3 has more to lose than layer 2 with ICMP.

Presentation: T. Woo. TCP PEP problem addressed. Simulation results. PEP 
operation & benefit. 

Q: What is a benchmark?
A: Simulation with the same bandwidth*delay. Several questions on 
examples, all answered. Comments on multiple clients and 
aggregation; comments on transparency.
Q: Do you have a solution? 
A: No, we would like the group to develop it.
Q: Why should it be done here? There are some solutions that are already out 
A (from the floor):  Because it is important to consider this problem in the 
context of a specific bad link (i.e., wireless link) and because it is 
important to try to find a solution to a suite of problems that arise in a 
specific context rather than rely on ad-hoc solutions. 

The chairs declare that the meeting is running out of time; the 
discussion, including the naming of the WG, should continue on the 
mailing list.

Volunteers are asked to fill the position of Document Editor.

The meeting adjourns on time. 


None received.