[PWE3] comments on draft-ietf-pwe3-hdlc-ppp-encap-mpls-05.txt
Stewart Bryant <stbryant@cisco.com> Fri, 08 July 2005 18:13 UTC
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Date: Fri, 08 Jul 2005 19:13:04 +0100
From: Stewart Bryant <stbryant@cisco.com>
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Subject: [PWE3] comments on draft-ietf-pwe3-hdlc-ppp-encap-mpls-05.txt
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-------- Original Message -------- Subject: comments on draft-ietf-pwe3-hdlc-ppp-encap-mpls-05.txt Date: Fri, 08 Jul 2005 17:37:34 +0100 From: Stewart Bryant <stbryant@cisco.com> To: 'Luca Martini' <lmartini@cisco.com> CC: pwe3@cisco.com Please don't forget the comments at http://www.ietf.org/mail-archive/web/pwe3/current/msg07088.html ------ Not sure that the following text add any value Although different layer 2 protocols require different information to be carried in this encapsulation, an attempt has been made to make the encapsulation as common as possible for all layer 2 protocols. Other layer 2 protocols are described in separate documents. [ATM] [ETHER] [FRAME] ------ I note that you do not describe the layering in this draft, or call it out explicitly. I think that you should import the layering text from one of the other drafts to show PSN label/PW label/CW. ------ 0 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |0 0 0 0|0 0 0 0|Res| Length | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2: MPLS PWE3 Control Word I think that you should call out the field descriptions as per other encaps, and include the definition. It's just cut and paste. ------ In the above diagram the first 4 bits are set to 0 in indicate PW data [ARCH]. Should be CW ------- The next 4 bits provide space for carrying protocol specific flags. These are not used for HDLC/PPP and they They MUST be set to 0 when transmitting, and MUST be ignored upon receipt. Why is frag not supported? ------- 3.1.2. Processing the sequence number 3.2. MTU Requirements The network MUST be configured with an MTU that is sufficient to transport the largest encapsulation frames. When MPLS is used as the tunneling protocol, for example, this is likely to be 12 or more bytes greater than the largest frame size. The methodology described in [FRAG] MAY be used to fragment encapsulated frames that exeeed the PSN MTU. However if [FRAG] is not used then if the ingress router determines that an encapsulated layer 2 PDU exceeds the MTU of the PSN tunnel through which it must be sent, the PDU MUST be dropped. So you do support frag, but you don't allocate the bits in Fig 2 ------- If a packet is received, on the attachment circuit, that exceeds the interface MTU paramater value [CONTROL] , it MUST be dropped. subTLV? -------- 4.2. Frame Relay Port Mode Figure 3 illustrates the concept of frame relay port mode or many- to-one mapping which is an OPTIONAL capability. I think that the diagram needs a bit of a clean-up to make it obvious there is a FIG 3a and a Fig 3b, it looks somewhat merged. -------- 5. Using an MPLS Label as the Demultiplexer Field To use an MPLS label as the demultiplexer field, a 32-bit label stack entry [MPLSENCAP] is simply prepended to the emulated PW encapsulation, and hence will appear as the bottom label of an MPLS label stack. This label may be called the "PW label". The particular emulated PW identified by a particular label value must be agreed by the ingress and egress LSRs, either by signaling (e.g, via the methods of [CONTROL]) or by configuration. Other fields of the label stack entry are set as follows. I think that this text is missing from the ATM draft ---------- 7. Security Considerations The ethernet pseudowire type is subject to all of the general The HDLC/PPP PW --------- Regards Stewart _______________________________________________ pwe3 mailing list pwe3@ietf.org https://www1.ietf.org/mailman/listinfo/pwe3
- [PWE3] comments on draft-ietf-pwe3-hdlc-ppp-encap… Stewart Bryant
- [PWE3] Re: comments on draft-ietf-pwe3-hdlc-ppp-e… Luca Martini