INTERNET DRAFT Weibin Zhao
Service Location Group Henning Schulzrinne
draft-zhao-slp-da-interaction-06.txt Columbia University
Expires: December 23, 2000 Erik Guttman
Sun Microsystems
June 23, 2000
mSLP - Mesh-enhanced Service Location Protocol
draft-zhao-slp-da-interaction-06.txt
Status of This Memo
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Abstract
This document presents mSLP - Mesh-enhanced Service Location
Protocol, which enhances SLPv2 with a scheme for the interaction of
Directory Agents (DAs). mSLP proposes to use a fully meshed peering
DA architecture. Peer DAs exchange service registration information,
and maintain the same consistent data for the shared scopes. mSLP
provides a reliable directory service for an SLP system. It also
greatly simplifies Service Agent (SA) registrations. mSLP is backward
compatible with SLPv2, and incremental deployment is supported.
1. Introduction
In the Service Location Protocol (RFC 2608 [1]), Directory Agents
(DAs) are introduced for caching service advertisements from Service
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Agents (SAs), and answering queries from User Agents (UAs). They
exist to enhance the performance and scalability of SLP.
When multiple DAs are present, how should they interact with each
other? This is an open issue in SLPv2. This document presents mSLP -
Mesh-enhanced Service Location Protocol, which enhances SLPv2 with a
scheme for the interaction of DAs. mSLP proposes that if DAs are
needed in an SLP system, a fully meshed peering DA architecture
should be used, i.e., more than one DA should be present for each
scope, and they should maintain a fully meshed peer relationship
(similar to IBGP [2]). Peer DAs exchange their data for the shared
scopes when they set up a peer relationship, and continue to exchange
new service registration information during the entire peering
period. As a result, they maintain the same consistent data for the
shared scopes. mSLP provides a reliable directory service for an SLP
system. It also greatly simplifies SA registrations The scalability
of SLP is thereby enhanced. mSLP is backward compatible with SLPv2,
and incremental deployment is supported.
The rest of this document is organized as follows: Section 2 defines
the terminology. Section 3 reviews the current DA message flows in
SLPv2. Section 4 defines the mesh-enhancement extension. In Section
5, we describe the DA peer relationship. In Section 6, we present
the message forwarding control among DAs. We discuss our design in
Section 7, list constants in Section 8, and give security
considerations in Section 9.
2. Terminology
Peer DAs
If two DAs have one or more scopes in common within one
administrative domain, they are peers. Peer DAs
coordinate with each other and store the same consistent
data for the shared scopes.
Peering TCP connection
A persistent TCP connection that is kept between a pair
of peer DAs for the entire peering period. It provides
a reliable communication channel for the peer DAs to
exchange messages. Therefore, a DA implementation is not
burdened by managing message retransmissions. Its
closing can be an indication of the termination of the
peer relationship.
Mesh-enhanced DA
A DA who maintains a peering TCP connection to each of
its peers and forwards service registration information
to its peers according to the rules given in this
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document. A mesh-enhanced DA MUST carry the "mesh-
enhanced" attribute keyword in its DAAdvert messages.
Mesh-aware SA
An SA who understands the "mesh-enhanced" attribute in a
DAAdvert message and uses the mesh-enhanced DA
capability accordingly.
3. DA Message Flows in SLPv2
This section reviews the current DA message flows in SLPv2. Figure 1
illustrates SA registrations with DAs. For each service registration
(SrvReg) and deregistration (SrvDeReg) message, a DA replies with a
service acknowledgment (SrvAck) message.
+----+ +----+
| | --- SrvReg/SrvDeReg --> | |
| SA | | DA |
| | <------- SrvAck ------- | |
+----+ +----+
Figure 1. SA Registrations
Figure 2 shows UA queries with DAs. A DA replies with a service reply
(SrvRply) message to a service request (SrvRqst) message, a service
type reply (SrvTypeRply) message to a service type request
(SrvTypeRqst) message, and an attribute reply (AttrRply) message to
an attribute request (AttrRqst) message.
+----+ +----+
| | ----- SrvTypeRqst/SrvRqst/AttrRqst ----> | |
| UA | | DA |
| | <---- SrvTypeRply/SrvRply/AttrRply ----- | |
+----+ +----+
Figure 2. UA Queries
Figure 3 depicts DA discovery. A DA replies with a unicast DA
advertisement (DAAdvert) message to a multicast SrvRqst message which
has "service:directory-agent" as service type.
+-------+ Multicast SrvRqst +----+
| | ----- (service:directory-agent) ----> | |
| UA/SA | | DA |
| | <-------- Unicast DAAdvert ---------- | |
+-------+ +----+
Figure 3. DA Discovery
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Figure 4 shows DA advertisements which are multicast periodically.
+----+ +-------+
| | | |
| DA | ---- Multicast DAAdvert ---> | UA/SA |
| | | |
+----+ +-------+
Figure 4. DA Advertisement
From Figure 1 to 4, we can see that SLPv2 does not define the message
flows among DAs. We will define these flows for the interaction of
DAs and refine above flows in the following sections.
4. Mesh-enhancement Extension
We define a new SLP extension - "mesh-enhancement extension" for
specifying the interaction operations of mesh-enhanced DAs. This
extension has a five-byte extension header, a one-byte field denoted
as "Action-ID", and an optional part of DA list. Figure 5
illustrates its format.
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Mesh-Enhancement Extension ID | Next Extension Offset (NEO) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| NEO, contd. | Action-ID | Number of DA URLs |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length of DA URL #1 | DA URL #1 \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
. . .
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Length of DA URL #N | DA URL #N \
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5. Mesh-Enhancement Extension
The Action-ID is used to specify the requested operations from the
receiving DA or to indicate the status information to the receiving
DA. Table 1 lists the defined Action-IDs.
Action-ID Abbreviation
0 No_Action
1 Mesh_Forward_Rqst
2 Data_Dump_Rqst
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3 Peer_Conn_Indication
4 Peer_DA_Indication
5 Peer_Conn_Keepalive
Table 1. Actions in Mesh-Enhancement Extension
No_Action: null operation. It is used to turn off other operations.
Mesh_Forward_Rqst: mesh forwarding request. It requests that the
receiving DA forward the message to all DAs (both mesh-enhanced and
non-mesh-enhanced) in the registration scope.
Data_Dump_Rqst: data dump request. It requests that the receiving DA
dump all the service registration data in the shared scopes to the
requesting DA.
Peer_Conn_Indication: peer connection indication. It informs the
receiving DA that this is a peering TCP connection.
Peer_DA_Indication: peer DAs indication. It carries the optional DA
list in the form of URLs. The receiving DA SHOULD peer with all DAs
in this list.
Peer_Conn_Keepalive: peer connection keepalive. It indicates that
this peering TCP connection is alive. The receiving DA SHOULD not
close it.
5. Peer Relationship
We use a set of fully meshed peering TCP connections among peer DAs.
A mesh-enhanced DA maintains a peer list. Each entry in this peer
list includes peer URL, shared scopes, boot timestamp, peering TCP
connection ID, and mesh flag. The boot timestamp is to identify a
rebooted peer. The peering TCP connection is used for message
forwarding. The mesh flag tells whether the peer is mesh-enhanced or
not. A mesh-enhanced DA adds an entry to its peer list whenever it
discovers a new peer, removes an entry from the peer list when it
finds the corresponding peer is down, and updates an entry when it
detects the corresponding peer is rebooted.
A peer relationship has three stages: setting up, keeping and tearing
down. We describe each stage in detail next. We consider the
situation where mesh-enhanced DAs, non-mesh-enhanced DAs, mesh-aware
SAs and non-mesh-aware SAs are coexisted. Our scheme works even if
multicast is NOT supported or a DA's multicast DAAdvert can not reach
all of its peer DAs.
5.1. Setting Up a Peer Relationship
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In SLP, each DA periodically sends DA Advertisement (DAAdvert)
messages to the administratively scoped SLP multicast [3] address
(239.255.255.253 is the default address in the IPv4 local scope). All
DAs listen to this address. A DAAdvert message from a mesh-enhanced
DA MUST carry the "mesh-enhanced" attribute keyword (Figure 6).
+-----+ +-----------+
| | | |
| DA1 | ------- Multicast DAAdvert ------> | DA2/UA/SA |
| | [attr = mesh-enhanced] | |
+-----+ +-----------+
Figure 6. Mesh-enhanced DA Advertisement
When a mesh-enhanced DA learns about a new peer (either mesh-enhanced
or non-mesh-enhanced), it creates a peering TCP connection to the
peer if such connection does not yet exist. The mesh-enhanced DA uses
this peering TCP connection to forward messages to the peer. The
peer, if mesh-enhanced, also uses this peering TCP connection to
forward messages in the opposite direction. Therefore, a peering TCP
connection MAY be set up between two mesh-enhanced DAs or between a
mesh-enhanced DA and a non-mesh-enhanced DA. In the latter case, the
message forwarding only goes in uni-direction from the mesh-enhanced
DA to the non-mesh-enhanced DA.
For a non-mesh-enhanced peer, the mesh-enhanced DA just sets up a
peering TCP connection with it and forwards message to it through the
peering TCP connection. But for a mesh-enhanced peer, the mesh-
enhanced DA MUST take the following additional steps:
(1) Peering Connection Indication. After a peering TCP connection is
established, the DA who initiates the connection sends a
"Peer_Conn_Indication" DAAdvert message (We mean the message has the
mesh-enhancement extension with the Action-ID set to
"Peer_Conn_Indication". Similar notation is used in the rest of this
document.) through the connection to mark it as the peering TCP
connection (Figure 7).
(1) "Peer_Conn_Indication" DAAdvert
+-----+ (2) "Peer_DA_Indication" DAAdvert +-----+
| | <----------------- (TCP) ----------------- | |
| DA1 | | DA2 |
| | ------------------ (TCP) ----------------> | |
+-----+ "Peer_DA_Indication" DAAdvert +-----+
Figure 7. Peering Connection and Peer DAs Indication
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(2) Peer DAs Indication. After sending the "Peer_Conn_Indication"
DAAdvert message, the mesh-enhanced DA sends a "Peer_DA_Indication"
DAAdvert message through the peering TCP connection (Figure 7). This
message carries a list of DAs that the receiving DA MUST peer with.
This DA list is constructed based on the sending DA's peer
information and the receiving DA's service scopes. More precisely,
this list includes those DAs in the sending DA's peer list that share
some scopes with the receiving DA.
How does a mesh-enhanced DA react when it receives the
"Peer_Conn_Indication" and "Peer_DA_Indication" DAAdvert messages?
When a mesh-enhanced DA receives a "Peer_Conn_Indication" DAAdvert
message, it SHOULD use the TCP connection from which the message is
received as the peering TCP connection to the sending DA instead of
establishing another one (There is a small possibility that a pair of
peering TCP connections might be created between the two peer DAs if
they try to set up a peering TCP connection to each other almost at
the same time.), and reply with a "Peer_DA_Indication" DAAdvert
message (Figure 7). By exchanging the peer information through
"Peer_DA_Indication" DAAdvert messages, the mesh-enhanced DAs can
learn about other DAs in the shared scopes even if multicast is not
supported (The initial peer relationships can be configured by hand
or through DHCP [4]).
The interaction sequence of in Figure 6 and 7 can be summarized as
follows (assume DA2 is mesh-enhanced):
DA1 is a mesh-enhanced peer of DA2:
<1> DA2 discovers DA1.
<2> DA2 creates peering TCP connection to DA1.
<3> DA2 sends "Peer_Conn_Indication" DAAdvert to DA1.
<4> DA2 sends "Peer_DA_Indication" DAAdvert to DA1.
<5> DA1 sends "Peer_DA_Indication" DAAdvert to DA2.
DA1 is a non-mesh-enhanced peer of DA2:
<1> DA2 discovers DA1.
<2> DA2 creates peering TCP connection to DA1.
When a mesh-enhanced DA receives a "Peer_DA_Indication" DAAdvert
message, it checks the DA list in the message. This DA list can be
empty in which case the number of DA URLs equals 0. If any URL in the
list is NOT in its peer list, the mesh-enhanced DA unicasts an active
DA discovery service request (a SrvRqst message with service type =
"service:directory-agent") to the DA corresponding to the URL, to
obtain a DAAdvert message from it (Figure 8). For example, if DA2
received the URL for DA3 from DA1 in the "Peer_DA_Indication"
DAAdvert message (Figure 7), and DA3 is NOT in DA2's peer list, DA2
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MUST then acquire a DAAdvert message from DA3 (Figure 8). Upon
receiving the DAAdvert message from DA3, DA2 can go through the whole
process to set up a peer relationship with DA3.
+-----+ Unicast SrvRqst +-----+
| | ----- (service:directory-agent) ----> | |
| DA2 | | DA3 |
| | <-------- Unicast DAAdvert ---------- | |
+-----+ +-----+
Figure 8. Obtaining DAAdvert
(3) Getting Data. After sending the "Peer_DA_Indication" DAAdvert
message, the mesh-enhanced DA SHOULD decide whether it needs to get
the data from the new peer. If it needs, it sends a "Data_Dump_Rqst"
DAAdvert message to the peer (Figure 9).
+-----+ "Data_Dump_Rqst" DAAdvert +-----+
| | -------------- (TCP) ------------> | |
| DA1 | | DA2 |
| | <--------- SrvReg (TCP) ---------- | |
+-----+ (data of shared scopes) +-----+
Figure 9. Dumping Data
Please note that a mesh-enhanced DA does not need to download data
from all of its new peers. For example, when a newly booted DA joins
a peering DA set of three DAs, it needs to get a copy of the existing
registration data from one of these three DAs, but not from all of
them, which incurs a lot of redundant transmissions. How to choose a
DA to download the data from the peering DA set is implementation
dependent. There are a variety of choices for doing this. The new DA
can randomly choose one DA from the peering DA set or just use the
first DA it found. Other criteria can also be used for the selection
such as the nearest DA or the most lightly loaded DA. The choice
only affects performance.
On the other hand, when a mesh-enhanced DA receives a
"Data_Dump_Rqst" DAAdvert message, it dumps all the data of the
shared scopes to the requesting DA. Each data record is sent as a
SrvReg message, with a re-calculated new lifetime (= old lifetime -
elapsed time). After exchanging their data in both directions, peer
DAs have the same consistent data for the shared scopes.
5.2. Keeping a Peer Relationship
In SLPv2, a DA could close an idle TCP connection after
CONFIG_CLOSE_CONN seconds (5 minutes at least). To keep a peering TCP
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connection alive, a mesh-enhanced DA SHOULD send a
"Peer_Conn_Keepalive" DAAdvert message via the channel every
CONFIG_DA_KEEPALIVE (see Section 8) seconds (Figure 10).
+-----+ +-----+
| | | |
| DA1 | ---------------- (TCP) ----------------> | DA2 |
| | "Peer_Conn_Keepalive" DAAdvert | |
+-----+ +-----+
Figure 10. DA Keepalive
5.3. Tearing Down a Peer Relationship
A mesh-enhanced DA SHOULD tear down a peer relationship when it finds
that the peer has closed the peering TCP connection; when it receives
a multicast DAAdvert message from the peer with a DA stateless boot
timestamp set to 0 meaning the peer is going to shutdown; or when it
has not received the keepalive DAAdvert message from the peer for
more than CONFIG_DA_KEEPALIVE seconds. In the last case, there may be
a network partition and peer DA states get inconsistent.
To tear down a peer relationship, a DA stops forwarding any service
registration information to this peer, closes TCP connection with
this peer, and removes this peer from its peer list.
6. Message Forwarding Control
6.1. Forwarding SrvReg and SrvDeReg Messages
A mesh-enhanced DA forwards new service registration information from
mesh-aware SAs. The forwarding rules are as follows:
(1) Explicit Forwarding: A message is forwarded only when it
explicitely requests to be forwarded. A mesh-aware SA needs to
attach the mesh-enhancement extension to a SrvReg or SrvDeReg message
and set the Action-ID to "Mesh_Forward_Rqst" if it wants the message
to be forwarded by a mesh-enhanced DA. This is for the compatibility
with SLPv2, where SAs need to register with all existing DAs. To
avoid unnecessary forwarding, the explicit forwarding rule is used.
(2) One-hop Forwarding: A SrvReg or SrvDeReg message is forwarded
only once by a mesh-enhanced DA to all of its peers (both mesh-
enhanced and non-mesh-enhanced) in the registration scope. Before
forwarding a message, a mesh-enhanced DA sets the Action-ID in the
mesh-enhancement extension to "No_Action". In this way, a forwarded
message will never be forwarded again. Since the peering DA set is
in a fully connected mesh, one-hop forwarding is enough to ensure
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that a message can reach all peer DAs. Figure 11 shows how a
SrvReg/SrvDeReg message is forwarded.
+----+ "Mesh_Forward_Rqst" +-----+ "No_Action" +-----+
| | -- SrvReg/SrvDeReg -> | | --- SrvReg/SrvDeReg --> | |
| SA | | DA1 | | DA2 |
| | <------ SrvAck ------ | | <------- SrvAck ------- | |
+----+ +-----+ +-----+
Figure 11. Forwarding Registration
(3) Handling SrvAck: A DA always replies with a SrvAck message when
it receives a SrvReg or SrvDeReg message. So a mesh-enhanced DA
SHOULD process SrvAck messages from other DAs.
6.2. Forwarding DAAdvert Messages
Besides forwarding service registration information from mesh-aware
SAs, a mesh-enhanced DA also forwards the DAAdvert messages from its
non-mesh-enhanced peers. The forwarding rules are as follows:
(1) A DAAdvert message is forwarded only when it comes from a new or
rebooted non-mesh-enhanced peer.
(2) The DAAdvert message is forwarded to all of its mesh-enhanced
peers that share some scopes with the advertised DA.
(3) A forwarded DAAdvert message SHOULD not be forwarded again. It
can be identified easily since the sending DA and advertised DA are
different for a forwarded DAAdvert message.
Forwarding the DAAdvert message from a new or rebooted non-mesh-
enhanced peer can ensure that the DA is known to all of its mesh-
enhanced peers even if multicast is NOT supported or its multicast
DAAdvert messages can NOT reach all of its mesh-enhanced peers. With
the peer setting up procedure described in Section 5.1 and the
forwarding rules given in this section, a DA (mesh-enhanced or non-
mesh-enhanced) known to one mesh-enhanced peer can be known to all of
its mesh-enhanced peers. Therefore, a mesh-enhanced DA can know all
of its peers (mesh-enhanced and non-mesh-enhanced), and forward
service registration information from mesh-aware SAs to them
properly.
7. Design Discussion
In this section, we discuss several important design issues.
7.1 Meshed Peering TCP Connections
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The fully meshed peering DA architecture is built on top of a set of
fully meshed peering TCP connections. We choose to use this set of
fully meshed peering TCP connections mainly because it greatly
facilitates message forwarding control. Any service registration
information received by a DA only needs one-hop forwarding to reach
all other DAs in the peering DA set. We anticipate a small number of
DAs for each service scope, and 2-4 is the recommended value. There
is no need to have separate DA for each scope. A DA can serve
multiple scopes, and a peering TCP connection is used for all shared
scopes between each pair of peer DAs.
7.2 Reliability
The fully meshed peering DA architecture provides maximum robustness.
It ensures that no single failure point exists in the SLP directory
service. All service registrations are kept by at least two DAs. If
one DA is down, at least one other peer DA can continue to provide
the service information for the scope. Moreover, the peering DA
architecture ensures the data consistency among peer DAs
automatically. It also enables a DA to recover from crash with much
less effort since a rebooted DA can get the existing data from its
peering DA set. This is done through DA coordination, no SA
involvement is needed.
7.3 Simplifying SA Registrations and Scalability
The fully meshed peering DA architecture greatly simplifies SA
registrations. A mesh-aware SA only needs to register with one
mesh-enhanced DA in the registration scope. The information will be
propagated automatically within the peering DA set. Thus, a mesh-
aware SA does not need to implement the complicated algorithm to
register with all existing DAs and to re-register when new mesh-
enhanced DAs are discovered, or old mesh-enhanced DAs are found to
have rebooted. With mesh-enhanced DAs and simplified SAs, the overall
SLP system scalability can be enhanced.
7.4 Forwarding UA Queries
A further extension to the interaction of SLP DAs is to forward UA
queries besides SA registrations. It works as follows: When a mesh-
enhanced DA receives a UA query which is not in its scope, it
forwards the query to another DA which supports the scope. This can
simplify UA implementation since UAs do not need to keep track of DA
scopes. A UA can send its queries to any mesh-enhanced DA. However,
this adds much complexity to the mesh-enhanced DA implementation.
First, a mesh-enhanced DA needs to keep track of all DAs of all
scopes, not only the DAs that share some scopes with it. Second, a
mesh-enhanced DA needs to forward the query to another DA, and it
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also needs to forward the reply from another DA back to the UA. We
did not include this extension in our scheme mainly due to its
complexity. However, for a thin-client UA implementation, it might
deserve further consideration.
7.5 Compatibility
mSLP is backward compatible with SLPv2. It only defines a new
attribute ("mesh-enhanced") for the DAAdvert message and a new SLP
extension (mesh-enhancement extension) which is used by DAAdvert,
SrvReg and SrvDeReg messages. In mSLP, DAs are enhanced with very
little added complexity, and the changes are almost transparent to
UAs and SAs. UAs can be kept unchanged. SAs can be greatly simplified
by using the mesh-forwarding capability for the service
registrations.
mSLP supports incremental deployment of mesh-enhanced DAs. A mesh-
enhanced DA MUST set up peer relationships with both mesh-enhanced
DAs and non-mesh-enhanced DAs. A mesh-aware SA only needs to register
with one mesh-enhanced DA. However, it still needs to take care of
newly found non-mesh-enhanced DAs and rebooted non-mesh-enhanced DAs
since these non-mesh-enhanced DAs can not get the existing data from
other DAs. Therefore, uniformly mesh-enhanced DAs can provide a much
easier job for mesh-aware SAs.
7.6 Summary
We summarize the operations for UAs, mesh-aware SAs, non-mesh-aware
SAs, mesh-enhanced DAs and non-mesh-enhanced DAs as follows:
UA
A UA MAY prefer to use a mesh-enhanced DA to a non-mesh-enhanced
DA since a mesh-enhanced DA is more likely to reliably contain
the complete set of current service registration data for the
UA's scope.
Non-mesh-aware SA
It needs to discover all DAs in its scope and register with all
of them. It does NOT use the mesh-enhancement extension.
Mesh-aware SA
It identifies mesh-enhanced DAs from the "mesh-enhanced"
attribute in the DAAdvert messages. It only needs to discover
one mesh-enhanced DA and register with it using a mesh-
enhancement extension with the Action-ID set to
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"Mesh_Forward_Rqst". If there are no mesh-enhanced DAs in its
scope, it operates in the same way as a non-mesh-aware SA [1].
Non-mesh-enhanced DA
It accepts SrvReg and SrvDeReg messages from SAs and mesh-
enhanced DAs normally. It dose NOT forward them.
Mesh-enhanced DA
(1) It MUST carry the "mesh-enhanced" attribute keyword in its
DAAdvert messages (Section 2).
(2) It MUST keep a list of peer DAs (mesh-enhanced and non-mesh-
enhanced) that share some scopes with it, and maintain a peering
TCP connection to each of them. For each mesh-enhanced peer, a
"Peer_Conn_Indication" DAAdvert message SHOULD be sent OR
processed, a "Peer_DA_Indication" DAAdvert message SHOULD be sent
AND processed, a "Data_Dump_Rqst" DAAdvert message MAY be sent OR
processed (Section 5).
(3) It accepts SrvReg and SrvDeReg messages from SAs and mesh-
enhanced DAs. It MUST forward the "Mesh_Forward_Rqst" SrvReg and
SrvDeReg to all peer DAs (both mesh-enhanced and non-mesh-
enhanced) in the registration scope. It also processes SrvAck
messages from mesh-enhanced DAs (Section 6.1).
(4) When it receives a DAAdvert messages from a new or rebooted
non-mesh-enhanced peer, it MUST forward the message to all of its
mesh-enhanced peers that share some scopes with the advertised DA
(Section 6.2).
8. Constants
Mesh-enhancement Extension ID 0x0006 (Section 4)
CONFIG_DA_KEEPALIVE 290 seconds (Section 5.2)
Note: CONFIG_DA_KEEPALIVE < CONFIG_CLOSE_CONN, which has a default
value of 300 seconds [1].
9. Security Considerations
DA authentication is more important in mSLP, since mesh-aware SAs
trust the mesh-enhanced DA they are sending the SrvReg and SrvDeReg
messages to to forward them. DAs SHOULD use standard SLPv2
authentication to authenticate other DAs in the mesh. DAs SHOULD also
perform authentication before accepting SrvReg and SrvDeReg messages
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to prevent illegitimate modification or elimination of legitimate
service registrations. mSLP is just as secure as SLPv2.
10. References
[1] E. Guttman, C. Perkins, J. Veizades, M. Day,
"Service Location Protocol Version 2", RFC 2608, June 1999.
[2] Y. Rekhter, T. Li, "A Border Gateway Protocol 4 (BGP-4)",
RFC 1771, March 1995.
[3] D. Meyer, "Administratively Scoped IP Multicast", RFC 2365,
July 1998.
[4] R. Droms, "Dynamic Host Configuration Protocol", RFC 2131,
March 1997.
11. Authors' Addresses
Weibin Zhao
Department of Computer Science
Columbia University
1214 Amsterdam Avenue, MC 0401
New York, NY 10027-7003
Email: zwb@cs.columbia.edu
Henning Schulzrinne
Department of Computer Science
Columbia University
1214 Amsterdam Avenue, MC 0401
New York, NY 10027-7003
Email: hgs@cs.columbia.edu
Erik Guttman
Sun Microsystems
Eichhoelzelstr. 7
74915 Waibstadt
Germany
Email: Erik.Guttman@sun.com
Zhao, et al. Expires: December 23, 2000 [Page 14]